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Islam MR, Ji F, Bansal M, Hua Y, Sigal IA. Fibrous finite element modeling of the optic nerve head region. Acta Biomater 2024; 175:123-137. [PMID: 38147935 DOI: 10.1016/j.actbio.2023.12.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 12/06/2023] [Accepted: 12/20/2023] [Indexed: 12/28/2023]
Abstract
The optic nerve head (ONH) region at the posterior pole of the eye is supported by a fibrous structure of collagen fiber bundles. Discerning how the fibrous structure determines the region biomechanics is crucial to understand normal physiology, and the roles of biomechanics on vision loss. The fiber bundles within the ONH structure exhibit complex three-dimensional (3D) organization and continuity across the various tissue components. Computational models of the ONH, however, usually represent collagen fibers in a homogenized fashion without accounting for their continuity across tissues, fibers interacting with each other and other fiber-specific effects in a fibrous structure. We present a fibrous finite element (FFE) model of the ONH that incorporates discrete collagen fiber bundles and their histology-based 3D organization to study ONH biomechanics as a fibrous structure. The FFE model was constructed using polarized light microscopy data of porcine ONH cryosections, representing individual fiber bundles in the sclera, dura and pia maters with beam elements and canal tissues as continuum structures. The FFE model mimics the histological in-plane orientation and width distributions of collagen bundles as well as their continuity across different tissues. Modeling the fiber bundles as linear materials, the FFE model predicts the nonlinear ONH response observed in an inflation experiment from the literature. The model also captures important microstructural mechanisms including fiber interactions and long-range strain transmission among bundles that have not been considered before. The FFE model presented here advances our understanding of the role of fibrous collagen structure in the ONH biomechanics. STATEMENT OF SIGNIFICANCE: The microstructure and mechanics of the optic nerve head (ONH) are central to ocular physiology. Histologically, the ONH region exhibits a complex continuous fibrous structure of collagen bundles. Understanding the role of the fibrous collagen structure on ONH biomechanics requires high-fidelity computational models previously unavailable. We present a computational model of the ONH that incorporates histology-based fibrous collagen structure derived from polarized light microscopy images. The model predictions agree with experiments in the literature, and provide insight into important microstructural mechanisms of fibrous tissue biomechanics, such as long-range strain transmission along fiber bundles. Our model can be used to study the microstructural basis of biomechanical damage and the effects of collagen remodeling in glaucoma.
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Affiliation(s)
- Mohammad R Islam
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Mechanical Engineering, University of Texas Rio Grande Valley, Edinburg TX, USA
| | - Fengting Ji
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh PA, USA
| | - Manik Bansal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Biomedical Engineering, University of Mississippi, MS, USA
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh PA, USA.
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Otani T, Miyata K, Miki A, Wada S. Computational study on the effects of central retinal blood vessels with asymmetric geometries on optic nerve head biomechanics. Med Eng Phys 2024; 123:104086. [PMID: 38365339 DOI: 10.1016/j.medengphy.2023.104086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 11/28/2023] [Accepted: 12/10/2023] [Indexed: 02/18/2024]
Abstract
Optic nerve head (ONH) biomechanics are associated with glaucoma progression and have received considerable attention. Central retinal vessels (CRVs) oriented asymmetrically in the ONH are the single blood supply source to the retina and are believed to act as mechanically stable elements in the ONH in response to intraocular pressure (IOP). However, these mechanical effects are considered negligible in ONH biomechanical studies and received less attention. This study investigated the effects of CRVs on ONH biomechanics taking into consideration three-dimensional asymmetric CRV geometries. A CRV geometry was constructed based on CRV centerlines extracted from optical coherence tomography ONH images in eight healthy subjects and superimposed in the idealized ONH geometry established in previous studies. Mechanical analyses of the ONH in response to the IOP were conducted in the cases with and without CRVs for comparison. Obtained results demonstrated that the CRVs induced anisotropic ONH deformation, particularly in the lamina cribrosa and the associated upper neural tissues (prelamina) with wide ranges of spatial strain distributions. These results indicated that the CRVs result in anisotropic deformation with local strain concentration, rather than function to mechanically support in response to the IOP as in the conventional thinking in ophthalmology.
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Affiliation(s)
- Tomohiro Otani
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, Japan.
| | - Kota Miyata
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, Japan
| | - Atsuya Miki
- Department of Myopia Control Research, Aichi Medical University, Japan
| | - Shigeo Wada
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyamacho, Toyonaka, Osaka 560-8531, Japan
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Lam MR, Yang CD, Colmenarez JA, Dong P, Gu L, Suh DW. The role of intrapartum fetal head compression in neonatal retinal hemorrhage. J AAPOS 2023; 27:267.e1-267.e7. [PMID: 37722620 DOI: 10.1016/j.jaapos.2023.07.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 07/20/2023] [Accepted: 07/22/2023] [Indexed: 09/20/2023]
Abstract
PURPOSE Neonatal retinal hemorrhage is a common finding in newborns, but the underlying mechanisms are not fully understood. A computational simulation was designed to study the events taking place in the eye and orbit when the head is compressed as the neonate passes through the birth canal. METHODS A finite element model of the eye, optic nerve sheath, and orbit was simulated and subjected to forces mimicking rises in intracranial pressure (ICP) associated with maternal contractions during normal vaginal delivery. Resulting changes in intraocular pressure (IOP), pressure in the optic nerve sheath, and stress within the sclera and retina were measured. RESULTS During contractions, increased ICP was transmitted to the orbit, globe, and optic nerve sheath. IOP rose by 2.71 kPa near the posterior pole. Pressure at the center of the optic nerve sheath rose by 7.31 kPa and up to 9.30 kPa at its interface with the sclera. Stress in the retina was highest near the optic disk and reached 10.93, 10.99, and 13.28 kPa in the preretinal, intraretinal, and subretinal layers, respectively. Stress in the sclera peaked at 12.76 kPa. CONCLUSIONS Increasing ICP associated with natural vaginal delivery increases intraorbital pressure, which applies stress to the retina. Associated retinal deformation may cause tearing of the retinal vasculature. Increased pressure within the optic nerve sheath may occlude the central retinal vein, resulting in outflow obstruction and subsequent rupture. Forces accumulated near the optic disk, likely accounting for the tendency of neonatal retinal hemorrhage to occur posteriorly.
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Affiliation(s)
- Matthew R Lam
- Creighton University School of Medicine, Phoenix, Arizona.
| | - Christopher D Yang
- Department of Ophthalmology and Visual Sciences, University of California, Irvine School of Medicine, Irvine, California; Gavin Herbert Eye Institute, University of California, Irvine, Irvine, California
| | - Jose A Colmenarez
- Department of Biomedical Engineering and Science, Florida Institute of Technology, Melbourne, Florida
| | - Pengfei Dong
- Department of Biomedical Engineering and Science, Florida Institute of Technology, Melbourne, Florida
| | - Linxia Gu
- Department of Biomedical Engineering and Science, Florida Institute of Technology, Melbourne, Florida
| | - Donny W Suh
- Department of Ophthalmology and Visual Sciences, University of California, Irvine School of Medicine, Irvine, California; Gavin Herbert Eye Institute, University of California, Irvine, Irvine, California
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Karimi A, Razaghi R, Rahmati SM, Girkin CA, Downs JC. Relative Contributions of Intraocular and Cerebrospinal Fluid Pressures to the Biomechanics of the Lamina Cribrosa and Laminar Neural Tissues. Invest Ophthalmol Vis Sci 2022; 63:14. [PMID: 36255364 PMCID: PMC9587471 DOI: 10.1167/iovs.63.11.14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 09/27/2022] [Indexed: 12/02/2022] Open
Abstract
Purpose The laminar region of the optic nerve head (ONH), thought to be the site of damage to the retinal ganglion cell axons in glaucoma, is continuously loaded on its anterior and posterior surfaces by dynamic intraocular pressure (IOP) and orbital cerebrospinal fluid pressure (CSFP), respectively. Thus, translaminar pressure (TLP; TLP = IOP-CSFP) has been proposed as a glaucoma risk factor. Methods Three eye-specific finite element models of the posterior human eye were constructed, including full 3D microstructures of the load-bearing lamina cribrosa (LC) with interspersed laminar neural tissues (NTs), and heterogeneous, anisotropic, hyperelastic material formulations for the surrounding peripapillary sclera and adjacent pia. ONH biomechanical responses were simulated using three combinations of IOP and CSFP loadings consistent with posture change from sitting to supine. Results Results show that tensile, compressive, and shear stresses and strains in the ONH were higher in the supine position compared to the sitting position (P < 0.05). In addition, LC beams bear three to five times more TLP-driven stress than interspersed laminar NT, whereas laminar NT exhibit three to five times greater strain than supporting LC (P < 0.05). Compared with CSFP, IOP drove approximately four times greater stress and strain in the LC, NT, and peripapillary sclera, normalized per mm Hg pressure change. In addition, IOP drove approximately three-fold greater scleral canal expansion and anterior-posterior laminar deformation than CSFP per mm Hg (P < 0.05). Conclusions Whereas TLP has been hypothesized to play a prominent role in ONH biomechanics, the IOP and CSFP effects are not equivalent, as IOP-driven stress, strain, and deformation play a more dominant role than CSFP effects.
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Affiliation(s)
- Alireza Karimi
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Reza Razaghi
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | | | - Christopher A. Girkin
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - J. Crawford Downs
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, Alabama, United States
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Urale PWB, Puckett AM, York A, Arnold D, Schwarzkopf DS. Highly accurate retinotopic maps of the physiological blind spot in human visual cortex. Hum Brain Mapp 2022; 43:5111-5125. [PMID: 35796159 PMCID: PMC9812231 DOI: 10.1002/hbm.25996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 05/18/2022] [Accepted: 06/15/2022] [Indexed: 01/15/2023] Open
Abstract
The physiological blind spot is a naturally occurring scotoma corresponding with the optic disc in the retina of each eye. Even during monocular viewing, observers are usually oblivious to the scotoma, in part because the visual system extrapolates information from the surrounding area. Unfortunately, studying this visual field region with neuroimaging has proven difficult, as it occupies only a small part of retinotopic cortex. Here, we used functional magnetic resonance imaging and a novel data-driven method for mapping the retinotopic organization in and around the blind spot representation in V1. Our approach allowed for highly accurate reconstructions of the extent of an observer's blind spot, and out-performed conventional model-based analyses. This method opens exciting opportunities to study the plasticity of receptive fields after visual field loss, and our data add to evidence suggesting that the neural circuitry responsible for impressions of perceptual completion across the physiological blind spot most likely involves regions of extrastriate cortex-beyond V1.
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Affiliation(s)
- Poutasi W. B. Urale
- School of Optometry & Vision ScienceUniversity of AucklandAucklandNew Zealand
| | - Alexander M. Puckett
- School of PsychologyUniversity of QueenslandBrisbaneQueenslandAustralia
- Queensland Brain InstituteUniversity of QueenslandBrisbaneQueenslandAustralia
| | - Ashley York
- School of PsychologyUniversity of QueenslandBrisbaneQueenslandAustralia
- Queensland Brain InstituteUniversity of QueenslandBrisbaneQueenslandAustralia
| | - Derek Arnold
- School of PsychologyUniversity of QueenslandBrisbaneQueenslandAustralia
- Queensland Brain InstituteUniversity of QueenslandBrisbaneQueenslandAustralia
| | - D. Samuel Schwarzkopf
- School of Optometry & Vision ScienceUniversity of AucklandAucklandNew Zealand
- Experimental PsychologyUniversity College LondonLondonUnited Kingdom
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Hua Y, Lu Y, Walker J, Lee PY, Tian Q, McDonald H, Pallares P, Ji F, Brazile BL, Yang B, Voorhees AP, Sigal IA. Eye-specific 3D modeling of factors influencing oxygen concentration in the lamina cribrosa. Exp Eye Res 2022; 220:109105. [PMID: 35568202 PMCID: PMC11007759 DOI: 10.1016/j.exer.2022.109105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 04/06/2022] [Accepted: 04/28/2022] [Indexed: 11/29/2022]
Abstract
Our goal was to identify the factors with the strongest influence on the minimum lamina cribrosa (LC) oxygen concentration as potentially indicative of conditions increasing hypoxia risk. Because direct measurement of LC hemodynamics and oxygenation is not yet possible, we developed 3D eye-specific LC vasculature models. The vasculature of a normal monkey eye was perfusion-labeled post-mortem. Serial cryosections through the optic nerve head were imaged using fluorescence and polarized light microscopy to visualize the vasculature and collagen, respectively. The vasculature within a 450 μm-thick region containing the LC - identified from the collagen, was segmented, skeletonized, and meshed for simulations. Using Monte Carlo sampling, 200 vascular network models were generated with varying vessel diameter, neural tissue oxygen consumption rate, inflow hematocrit, and blood pressures (arteriole, venule, anterior boundary, and posterior boundary). Factors were varied over ranges of baseline ±20% with uniform probability. For each model we first obtained the blood flow, and from this the neural tissue oxygen concentration. ANOVA was used to identify the factors with the strongest influence on the minimum (10th percentile) oxygen concentration in the LC. The three most influential factors were, in ranked order, vessel diameter, neural tissue oxygen consumption rate, and arteriole pressure. There was a strong interaction between vessel diameter and arteriole pressure whereby the impact of one factor was larger when the other factor was small. Our results show that, for the eye analyzed, conditions that reduce vessel diameter, such as vessel compression due to elevated intraocular pressure or gaze-induced tissue deformation, may particularly contribute to decreased LC oxygen concentration. More eyes must be analyzed before generalizing.
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Affiliation(s)
- Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Yuankai Lu
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Jason Walker
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA, United States
| | - Po-Yi Lee
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Qi Tian
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Haiden McDonald
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA, United States
| | - Pedro Pallares
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA, United States
| | - Fengting Ji
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States
| | - Bryn L Brazile
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Bin Yang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Engineering, Rangos School of Health Sciences, Duquesne University, Pittsburgh, PA, United States
| | - Andrew P Voorhees
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States.
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Jiang S, Turco B, Choudhry N. VASCULAR PERFUSION DENSITY MAPPING USING OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY COMPARING NORMAL AND OPTIC DISK PIT EYES. Retin Cases Brief Rep 2022; 16:126-132. [PMID: 31688795 DOI: 10.1097/icb.0000000000000908] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
PURPOSE Optic disk pits (ODPs) are typically detected incidentally as small, gray, unilateral, oval-shaped excavation in the temporal optic disk on routine fundus examination. In this cross-sectional retrospective case series, we report optical coherence tomography angiography findings in patients with unilateral ODPs and describe changes in vessel perfusion associated with ODP. METHODS A total of eight eyes (four with ODP and four normal contralateral) were included in this study. Patients were excluded if any other optic disk abnormalities were present. Spectral-domain optical coherence tomography angiography (AngioVue; Optovue, Fremont, CA) imaging was conducted to map the vascularization of three layers in the optic nerve over a 4.5-mm × 4.5-mm region. The radial peripapillary capillaries, the nerve head capillaries, and the choriocapillaris were automatically segmented based on the OCT system software, and the capillary perfusion density (CPD) was quantified for each layer. Kruskal-Wallis one-way analysis of variance was used to compare CPD in normal and ODP eyes of four patients with monocular ODP. RESULTS Overall, CPD was lower in eyes with ODP compared with the contralateral normal eye in the radial peripapillary capillary (0.4521 ± 0.08 vs. 0.5505 ± 0.03, P = 0.08) and nerve head capillary layers (0.5461 ± 0.08 vs. 0.5989 ± 0.01, P = 0.08). Significantly lower CPD values were associated with ODP eyes in the radial peripapillary capillary layer within the disk (P = 0.04), inferior nasal (P = 0.04), and temporal (P = 0.02) regions and in the nerve head vessel layer within the disk region (P = 0.04). Significantly higher CPD values were associated with ODP eyes in the choriocapillaris layer within the nasal (P = 0.02), superior temporal (P = 0.02), and inferior temporal (P = 0.02) regions. Visual acuity was also decreased in ODP eyes at 0.4 ± 0.3 logarithm of the minimum angle of resolution units (20/50) compared with normal eyes at 0.1 ± 0.1 logarithm of the minimum angle of resolution units (20/25) (P = 0.12). CONCLUSION This study demonstrated that the presence of an ODP is associated with decreased vascular density in some regions of the optic disk and reduced visual acuity.
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Affiliation(s)
- Shangjun Jiang
- Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Bryen Turco
- Wayne State University School of Medicine, Detroit, Michigan
| | - Netan Choudhry
- Vitreous Retina Macula Specialists of Toronto, Etobicoke, Ontario, Canada; and
- Department of Ophthalmology and Visual Sciences, University of Toronto, Toronto, Ontario, Canada
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Park KS, Lim HB, Shin YI, Park GS, Lee WH, Kim JY. Effect of axial length on peripapillary microvasculature: An optical coherence tomography angiography study. PLoS One 2021; 16:e0258479. [PMID: 34648529 PMCID: PMC8516294 DOI: 10.1371/journal.pone.0258479] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 09/28/2021] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE To investigate the effects of axial length (AL) on the peripapillary microvascular density acquired from optical coherence tomography angiography (OCTA). METHODS Retrospective observational study. A total of 111 eyes from 111 normal healthy subjects were examined. The subjects were divided into three groups according to the AL: Group 1 (AL: < 24.0 mm; 35 eyes), Group 2 (AL: 24.0-25.99 mm; 37 eyes), and Group 3 (AL: ≥ 26 mm; 39 eyes). Peripapillary OCTA images were acquired using 6× 6 mm angiography scans, and vessel density (VD) and perfusion density (PD) of the superficial capillary plexus were calculated automatically. VD and PD were compared among the three groups according to the distance from the optic disc (inner and outer rings). Linear regression analyses were also performed to identify clinical factors associated with average VD. RESULTS The average ALs of Groups 1-3 were 23.33± 0.57, 25.05± 0.60, and 27.42± 0.82, respectively. Average VD (P = 0.009) and PD (P = 0.029) in the inner ring increased with increasing AL. However, average VD (P < 0.001) and PD (P < 0.001) in the outer ring decreased with AL increased; the same trends were found for the full areas (VD, p<0.001; PD, p = 0.001). Average VDs in the inner and outer rings were not associated (P = 0.938). CONCLUSIONS Peripapillary VD and PD were significantly associated with AL. Depending on the distance from the disc, peripapillary VDs and PDs of the inner and outer rings were differentially affected by AL. Physicians should therefore consider the effects of AL in the analyses of peripapillary microvasculature.
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Affiliation(s)
- Kee Sup Park
- Department of Ophthalmology, Chungnam National University College of Medicine, Daejeon, Republic of Korea
- Department of Ophthalmology, Konyang University College of Medicine, Daejeon, Republic of Korea
| | - Hyung Bin Lim
- Department of Ophthalmology, Chungnam National University College of Medicine, Daejeon, Republic of Korea
- Myung Eye Clinic, Daejeon, Republic of Korea
| | - Yong Il Shin
- Department of Ophthalmology, Chungnam National University College of Medicine, Daejeon, Republic of Korea
- Rhee’s Eye Hospital, Daejeon, Republic of Korea
| | - Gi Seok Park
- Department of Ophthalmology, Chungnam National University College of Medicine, Daejeon, Republic of Korea
| | - Woo Hyuk Lee
- Department of Ophthalmology, Chungnam National University College of Medicine, Daejeon, Republic of Korea
- Department of Ophthalmology, Gyeongsang University College of Medicine Changwon Hospital, Changwon, Korea
| | - Jung-Yeul Kim
- Department of Ophthalmology, Chungnam National University College of Medicine, Daejeon, Republic of Korea
- * E-mail:
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Qian X, Li R, Lu G, Jiang L, Kang H, Kirk Shung K, Humayun MS, Zhou Q. Ultrasonic elastography to assess biomechanical properties of the optic nerve head and peripapillary sclera of the eye. Ultrasonics 2021; 110:106263. [PMID: 33065466 PMCID: PMC7736296 DOI: 10.1016/j.ultras.2020.106263] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 08/13/2020] [Accepted: 09/22/2020] [Indexed: 05/30/2023]
Abstract
PURPOSE To quantitatively investigate both optic nerve head (ONH) and peripapillary sclera (PPS) biomechanical properties of porcine eyes through an ultrasonic elastography imaging system in response to both increasing and decreasing intraocular pressure (IOP). METHODS The Young's modulus of the ONH and PPS were assessed using our high resolution ultrasonic imaging system which utilized a mechanical shaker to induce shear waves and an off-axis aligned 40 MHz needle transducer to track micron-level displacement along the direction of wave propagation. In this study, imaging on a total of 8 ex vivo porcine eyes preloaded with IOPs from 6 mmHg to 30 mmHg was performed. To have a better understanding of the effect of varying IOP on biomechanics, both increasing and decreasing IOPs were investigated. RESULTS The increase of the Young's modulus of ONH (92.4 ± 13.9 kPa at 6 mmHg to 224.7 ± 71.1 kPa at 30 mmHg) and PPS (176.8 ± 14.3 kPa at 6 mmHg to 573.5 ± 64.4 kPa at 30 mmHg) following IOP elevation could be observed in the reconstructed Young's modulus of the shear wave elasticity (SWE) imaging while the B-mode structural images remained almost unchanged. In addition, for the same IOP level, both ONH and PPS have a tendency to be stiffer with decreasing IOP as compared to increasing IOP. CONCLUSIONS Our results demonstrate the feasibility of using our ultrasonic elastography system to investigate the stiffness mapping of posterior eye with high resolution in both increasing and decreasing IOPs, making this technique potentially useful for glaucoma.
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Affiliation(s)
- Xuejun Qian
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA; USC Roski Eye Institute, University of Southern California, Los Angeles, CA 90033, USA
| | - Runze Li
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA; USC Roski Eye Institute, University of Southern California, Los Angeles, CA 90033, USA
| | - Gengxi Lu
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA; USC Roski Eye Institute, University of Southern California, Los Angeles, CA 90033, USA
| | - Laiming Jiang
- USC Roski Eye Institute, University of Southern California, Los Angeles, CA 90033, USA
| | - Haochen Kang
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - K Kirk Shung
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
| | - Mark S Humayun
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA; USC Roski Eye Institute, University of Southern California, Los Angeles, CA 90033, USA
| | - Qifa Zhou
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA; USC Roski Eye Institute, University of Southern California, Los Angeles, CA 90033, USA.
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Ko MWL, Lai CCC, Ng PCK, Chow BHY, Woo MJS, Yim KHC, Kim JR. Investigation of the Optic Nerve Head Morphology Influence to the Optic Nerve Head Biomechanics - Population Specific Model. Annu Int Conf IEEE Eng Med Biol Soc 2020; 2019:5374-5377. [PMID: 31947070 DOI: 10.1109/embc.2019.8856300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Glaucoma is an eye disorder potentially leading to permanent blindness through the damage of optic nerves at the optic nerve head (ONH). As a critical region of optic nerve damage, the porous Lamina Cribrosa (LC) in the ONH plays a critical role in determining whether optic nerves passing through will experience apoptosis in response to shear stress. The primary cause of shear stress to the LC is the increase in intraocular pressure (IOP). Since morphology governs how mechanical stresses distributes, LC morphology could be an important factor in determining the risks of glaucoma development and progression. The current project aims at investigating how anterior LC surface morphology impacts its response to shear stress caused by IOP. Results of the current study show that steeper LC morphologies could be associated with increased average shear stress on the anterior LC surface. The effect of LC morphology was comparable to that of IOP. This highlights the potential significance of LC morphology on the distribution of IOP-induced shear stress and calls for further investigation in this area.
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Satekenova E, Ko MWL, Kim JR. Investigation of the Optic Nerve Head Morphology Influence to the Optic Nerve Head Biomechanics - Patient Specific Model. Annu Int Conf IEEE Eng Med Biol Soc 2020; 2019:5370-5373. [PMID: 31947069 DOI: 10.1109/embc.2019.8856743] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Glaucoma is associated with damage and death of optic nerve fibers within the Lamina Cribrosa (LC) region of the Optic Nerve Head. The pathogenesis of the disease is unclear, and the anterior LC surface morphology of different individuals can be one of the possible contributor of glaucoma development and progression. The current study evaluates the relationship between the LC surface curvature and distribution of shear stresses on the LC surface. The patient-specific reconstructed ocular model was developed and analyzed in a finite element analysis software. In addition, the effect of elastic modulus of both sclera and LC on the shear stress was examined. Results showed that there is a correlation between the shear stress distribution and the curvature of the anterior LC surface. This finding highlights the potential significance of the LC morphology on the distribution of LC shear stress and require further investigation.
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Xu L, Freedman SF, Silverstein E, Muir K, El-Dairi M. Longitudinal reproducibility of spectral domain optical coherence tomography in children with physiologic cupping and stable glaucoma. J AAPOS 2019; 23:262.e1-262.e6. [PMID: 31513901 DOI: 10.1016/j.jaapos.2019.05.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 05/07/2019] [Accepted: 05/20/2019] [Indexed: 12/27/2022]
Abstract
PURPOSE To determine whether Spectralis (Heidelberg, Germany) spectral domain optical coherence tomography (SD-OCT) measurements are reproducible over time in children with physiologic cupping and stable glaucoma. METHODS Subjects were identified from a subset of participants in an earlier retrospective study conducted by our group and included children (<18 years of age) with physiologic cupping and stable primary congenital glaucoma (PCG) having had at least 2 SD-OCTs over a period of more than 1 between April 2010 and September 2015. Thicknesses of average peripapillary retinal nerve fiber layer (pRNFL) and six individual sectors and volumes of three segmented retinal layers and total retina were measured. Spectralis review software was used for segmentation. Intraclass correlation coefficients (ICC) and coefficient of variation (COV) were calculated. RESULTS A total of 35 eyes of 35 children were included: 15 eyes had physiologic cupping; 20 eyes, PCG. Mean ages at initial SD-OCT were 11.2 ± 3.3 years and 9.7 ± 3.3, respectively; mean intervals between first and last imaging were 2.2 ± 1.1 and 3.0 ± 1.4 years, respectively. ICCs across three visits for both groups for average and sectoral pRNFL thicknesses were 0.887-0.997 and for segmented retinal volumes were 0.806-0.993. ICCs for total retinal volume for physiologic cupping and PCG were 0.993 and 0.954, respectively. COVs for average pRNFL thickness were 0.9% and 1.7%, respectively. For all other measurements, COVs ranged from 0.3% to 5.4%. CONCLUSIONS Reproducibility of longitudinal SD-OCT measurements for average pRNFL thickness in children with stable glaucoma over about 2 years is comparable to short-term reproducibility (COV) in normal children (1.16%) and normal and glaucoma adults (1.62%-3.4%).
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Affiliation(s)
- Limin Xu
- Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts
| | - Sharon F Freedman
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina
| | - Evan Silverstein
- Department of Ophthalmology, Virginia Commonwealth University, Richmond, Virginia
| | - Kelly Muir
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina
| | - Mays El-Dairi
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina.
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Casado A, Cerveró A, López-de-Eguileta A, Fernández R, Fonseca S, González JC, Pacheco G, Gándara E, Gordo-Vega MÁ. Topographic correlation and asymmetry analysis of ganglion cell layer thinning and the retinal nerve fiber layer with localized visual field defects. PLoS One 2019; 14:e0222347. [PMID: 31509597 PMCID: PMC6738661 DOI: 10.1371/journal.pone.0222347] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 08/27/2019] [Indexed: 11/18/2022] Open
Abstract
Purpose To evaluate the accuracy of the measurement of the ganglion cell layer (GCL) of the posterior pole analysis (PPA) software of the Spectralis spectral-domain (SD) optical coherence tomography (OCT) device (Heidelberg Engineering, Inc., Heidelberg, Germany), the asymmetry of paired GCL sectors, the total retinal thickness asymmetry (RTA), and the peripapillary retinal nerve fiber layer (pRNFL) test to discriminate between healthy, early and advanced glaucoma eyes. Methods Three hundred eighteen eyes of 161 individuals with reliable visual fields (VF) were enrolled in this study. All participants were examined using the standard posterior pole and the pRNFL protocols of the Spectralis OCT device. VF impairment was graded in hemifields, and the GCL sectors were correlated with this damage. Thicknesses of each GCL, the GCL map deviation asymmetry and the pRNFL were compared between control and glaucomatous eyes. The area under the receiver operating characteristic curve (AUC) of these analyses was assessed. Results Fourteen of the 16 sectors of the GCL and pRNFL were significantly thinner in eyes with glaucoma than in control eyes (p<0.006). Similarly, the GCL map deviation showed a significant difference between these eyes and both the control eyes as well as the eyes with early glaucoma (p = 0.001 and p = 0.039, respectively). The highest values of AUC to diagnose both early and advanced glaucoma corresponded to the average pRNFL analysis and the GCL map deviation (AUC>0.823, p<0.040 and AUC>0.708, p<0.188, respectively). Conclusions Although 16 central sectors of the GCL observed with PPA showed good correlation with VF damage, the pRNFL and the GCL map deviation were more effective for discrimination of glaucomatous damage.
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Affiliation(s)
- Alfonso Casado
- Department of Ophthalmology, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain
| | - Andrea Cerveró
- Department of Ophthalmology, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain
- * E-mail:
| | - Alicia López-de-Eguileta
- Department of Ophthalmology, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain
| | - Raúl Fernández
- Department of Ophthalmology, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain
| | - Soraya Fonseca
- Department of Ophthalmology, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain
| | - Juan Carlos González
- Department of Ophthalmology, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain
| | - Gema Pacheco
- Department of Ophthalmology, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain
| | - Elena Gándara
- Department of Ophthalmology, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain
| | - Miguel Á. Gordo-Vega
- Department of Ophthalmology, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain
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Hung CH, Lee SH, Lin SY, Lin SL, Chen YC. The relationship between optic nerve head deformation and visual field defects in myopic eyes with primary open-angle glaucoma. PLoS One 2019; 13:e0209755. [PMID: 30596728 PMCID: PMC6312218 DOI: 10.1371/journal.pone.0209755] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 12/11/2018] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To investigate the relationship between the morphologic features of myopic optic nerve head (ONH) and visual field (VF) defects in myopic subjects with primary open-angle glaucoma (POAG) by intraindividual comparison. METHODS Myopic POAG subjects with unilateral glaucomatous VF defect were recruited. The morphologic features of myopic ONH, including optic disc tilt, optic disc rotation, and β-zone parapapillary atrophy (PPA) were measured from color fundus photographs. The comparisons were performed between the eyes with VF defects and the contralateral eyes without VF defects. Logistic regression analysis was performed to investigate the relationship between various ocular parameters and the presence of VF defects. RESULTS We retrospectively included 100 eyes of 50 myopic POAG subjects. (Mean age: 50.1 ± 10.0 years). The tilt ratio was similar between the paired eyes. The degree of optic disc rotation (12.96 ± 7.21°) in eyes with VF defects were statistically greater than the contralateral eyes (6.86 ± 4.30°; P < 0.001) without VF defect. The β-zone PPA-to-disc area ratio was significantly greater in eyes with VF defects than the contralateral eyes (P = 0.024) without VF defect. In multivariate logistic regression analysis, the greater degree of optic disc rotation was significantly associated with the presence of VF defects (P < 0.001). However, tilt ratio, β-zone PPA-to-disc area ratio, refractive error, and axial length were not associated with the presence of VF defects. CONCLUSIONS Among the morphologic features of myopic ONH, only the greater degree of the optic disc rotation was associated with the presence of VF defects in myopic subjects with POAG.
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Affiliation(s)
- Chih-Heng Hung
- Department of Ophthalmology, Cathay General Hospital, Taipei, Taiwan
| | - Shwu-Huey Lee
- Department of Ophthalmology, Cathay General Hospital, Taipei, Taiwan
| | - Szu-Yuan Lin
- Department of Ophthalmology, Cathay General Hospital, Taipei, Taiwan
| | - Shun-Ling Lin
- Department of Ophthalmology, Cathay General Hospital, Taipei, Taiwan
| | - Yi-Chun Chen
- Department of Ophthalmology, Cathay General Hospital, Taipei, Taiwan
- * E-mail:
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Voorhees AP, Jan NJ, Hua Y, Yang B, Sigal IA. Peripapillary sclera architecture revisited: A tangential fiber model and its biomechanical implications. Acta Biomater 2018; 79:113-122. [PMID: 30142444 DOI: 10.1016/j.actbio.2018.08.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 08/09/2018] [Accepted: 08/17/2018] [Indexed: 01/29/2023]
Abstract
The collagen fiber architecture of the peripapillary sclera (PPS), which surrounds the scleral canal, is a critical factor in determining the mechanical response of the optic nerve head (ONH) to variations in intraocular pressure (IOP). Experimental and clinical evidence point to IOP-induced deformations within the scleral canal as important contributing factors of glaucomatous neural tissue damage and consequent vision loss. Hence, it is imperative to understand PPS architecture and biomechanics. Current consensus is that the fibers of the PPS form a closed ring around the canal to support the delicate neural tissues within. We propose an alternative fiber architecture for the PPS, in which the scleral canal is supported primarily by long-running fibers oriented tangentially to the canal. We present evidence that this tangential model is consistent with histological observations in multiple species, and with quantitative measurements of fiber orientation obtained from small angle light scattering and wide-angle X-ray scattering. Using finite element models, we investigated the biomechanical implications of a tangential fiber PPS architecture. We found that the tangential arrangement of fibers afforded better mechanical support to the tissues within the scleral canal as compared to a simple circumferential ring of fibers or a combination of fibers oriented radially and circumferentially. We also found that subtle variations from a tangential orientation could reproduce clinically observed ONH behavior which has yet to be explained using current theories of PPS architecture and simulation, namely, the contraction of the scleral canal under elevated IOP. STATEMENT OF SIGNIFICANCE It is hypothesized that vision loss in glaucoma is due to excessive mechanical deformation within the neural tissue inside the scleral canal. This study proposes a new model for how the collagen of the peripapillary sclera surrounding the canal is organized to support the delicate neural tissue inside. Previous low-resolution studies of the peripapillary sclera suggested that the collagen fibers are arranged in a ring around the canal. Instead, we provide microscopic evidence suggesting that the canal is also supported by long-running interwoven fibers oriented tangentially to the canal. We demonstrate that this arrangement has multiple biomechanical advantages over a circular collagen arrangement and can explain previously unexplained experimental findings including contraction of the scleral canal under elevated intraocular pressure.
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Affiliation(s)
- Andrew P Voorhees
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ning-Jiun Jan
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Yi Hua
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Bin Yang
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ian A Sigal
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA, USA.
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Yamashita T, Sakamoto T, Yoshihara N, Terasaki H, Tanaka M, Kii Y, Nakao K. Correlations between local peripapillary choroidal thickness and axial length, optic disc tilt, and papillo-macular position in young healthy eyes. PLoS One 2017; 12:e0186453. [PMID: 29023585 PMCID: PMC5638527 DOI: 10.1371/journal.pone.0186453] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Accepted: 10/02/2017] [Indexed: 11/21/2022] Open
Abstract
Optical coherence tomography (OCT) has made it possible for clinicians to measure the peripapillary choroidal thickness (ppCT) noninvasively in various ocular diseases. However, the ocular factors associated with the ppCT have not been conclusively determined. The purpose of this study was to determine the relationship between the local ppCT and the axial length, optic disc tilt, and the angle of the papillo-macular position (PMP) in healthy eyes. This was a prospective, observational cross-sectional study of 119 right eyes of 119 healthy Japanese volunteers. The ppCT was manually measured at eight sectors around the optic disc using the B-scan images of the Topcon 3D OCT RNFL 3.4 mm circle scan. The trajectory of the retinal pigment epithelium in the B-scan image was fitted to a sine curve using ImageJ, and the amplitude of the sine curve was used to determine the degree of the optic disc tilt. The PMP angle was determined in the color fundus photographs. The relationships between the ppCT and the axial length, the optic disc tilt, and PMP angle were determined by Spearman and multiple correlation analyses. The mean age was 25.8 ± 3.9 years and the mean axial length was 25.5 ± 1.4 mm. The ppCT was significantly and negatively associated with the axial length (R = -0.43 to -0.24, P<0.01) and positively associated with the PMP angle (R = 0.28 to 0.37, P<0.01) in all eight circumpapillary sectors. The temporal and infratemporal ppCTs were significantly and negatively associated with the optic disc tilt (R = -0.31, -0.20, P<0.05). The results of multiple regression analyses were similar to that of Spearman correlation analysis. In conclusion, the axial length and PMP angle can affect the ppCT in all circumferential sectors, however the tilt of the optic disc is correlated with only some of the sectors. This should be remembered in interpreting the ppCT.
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Affiliation(s)
- Takehiro Yamashita
- Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Taiji Sakamoto
- Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
- * E-mail:
| | - Naoya Yoshihara
- Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Hiroto Terasaki
- Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Minoru Tanaka
- Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Yuya Kii
- Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - Kumiko Nakao
- Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
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Qian CS, Brascamp JW, Liu T. On the functional order of binocular rivalry and blind spot filling-in. Vision Res 2017; 136:15-20. [PMID: 28502775 DOI: 10.1016/j.visres.2017.04.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2017] [Revised: 04/11/2017] [Accepted: 04/25/2017] [Indexed: 11/18/2022]
Abstract
Binocular rivalry is an important phenomenon for understanding the mechanisms of visual awareness. Here we assessed the functional locus of binocular rivalry relative to blind spot filling-in, which is thought to transpire in V1, thus providing a reference point for assessing the locus of rivalry. We conducted two experiments to explore the functional order of binocular rivalry and blind spot filling-in. Experiment 1 examined if the information filled-in at the blind spot can engage in rivalry with a physical stimulus at the corresponding location in the fellow eye. Participants' perceptual reports showed no difference between this condition and a condition where filling-in was precluded by presenting the same stimuli away from the blind spot, suggesting that the rivalry process is not influenced by any filling-in that might occur. In Experiment 2, we presented the fellow eye's stimulus directly in rivalry with the 'inducer' stimulus that surrounds the blind spot, and compared it with two control conditions away from the blind spot: one involving a ring physically identical to the inducer, and one involving a disc that resembled the filled-in percept. Perceptual reports in the blind spot condition resembled those in the 'ring' condition, more than those in the latter, 'disc' condition, indicating that a perceptually suppressed inducer does not engender filling-in. Thus, our behavioral data suggest binocular rivalry functionally precedes blind spot filling-in. We conjecture that the neural substrate of binocular rivalry suppression includes processing stages at or before V1.
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Affiliation(s)
- Cheng S Qian
- Department of Psychology, Michigan State University, United States
| | - Jan W Brascamp
- Department of Psychology, Michigan State University, United States; Neuroscience Program, Michigan State University, United States
| | - Taosheng Liu
- Department of Psychology, Michigan State University, United States; Neuroscience Program, Michigan State University, United States.
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Laspas P, Culmann PD, Grus FH, Prokosch-Willing V, Poplawksi A, Pfeiffer N, Hoffmann EM. Revision of encapsulated blebs after trabeculectomy: Long-term comparison of standard bleb needling and modified needling procedure combined with transconjunctival scleral flap sutures. PLoS One 2017; 12:e0178099. [PMID: 28542372 PMCID: PMC5436863 DOI: 10.1371/journal.pone.0178099] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 05/06/2017] [Indexed: 11/19/2022] Open
Abstract
PURPOSE To compare two surgical approaches for treating encapsulated blebs after trabeculectomy with mitomycin C, in terms of the development of intraocular pressure and progression of glaucoma in a long-term follow up: 1. bleb needling alone vs. 2. a combined approach of needling with additional transconjunctival scleral flap sutures, to prevent early ocular hypotony. METHODS Forty-six patients with failing blebs after trabeculectomy with mitomycin C were enrolled in this study. Patients received either needling revision alone (group 1; n = 23) or a combined needling with additional transconjuctival flap sutures, if intraoperatively the intraocular pressure was estimated to be low (group 2; n = 23). Intraocular pressure (IOP), visual acuity, visual fields, and optic nerve head configuration by means of Heidelberg Retina Tomograph (HRT®) were analysed over time. Results from both groups were compared using Mann-Whitney U-test for single timepoints. RESULTS IOP did not differ significantly between the two groups during follow-up at three months (P = 0.13), six months (P = 0.12), one year (P = 0.92) and two years (P = 0.57) after surgery. Furthermore, there was no significant difference in the course of glaucoma concerning the optic nerve anatomy between the two groups (Rim Area Change in the Moorfields Regression Analysis of HRT®) till two years after surgery (P = 0.289). No functional impairment in visual acuity and visual fields was found in the groups of the study. CONCLUSIONS Single needling procedure is a standard successful method for restoring the function of encapsulated blebs. Postoperative hypotony represents a possible hazard, which can be minimized by additional transconjunctival flap sutures. Long-term results suggest that this modification is equally effective in lowering the IOP and preventing the progression of glaucoma as the standard needling procedure. To our knowledge this is the first study to investigate the long-term effect of tranconjunctival sutures for the prevention of hypotony.
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Affiliation(s)
- P. Laspas
- Department of Ophthalmology, University Medical Center, Johannes Gutenberg- University Mainz, Mainz, Germany
- * E-mail:
| | - P. D. Culmann
- Department of Ophthalmology, University Medical Center, Johannes Gutenberg- University Mainz, Mainz, Germany
| | - F. H. Grus
- Department of Ophthalmology, University Medical Center, Johannes Gutenberg- University Mainz, Mainz, Germany
| | - V. Prokosch-Willing
- Department of Ophthalmology, University Medical Center, Johannes Gutenberg- University Mainz, Mainz, Germany
| | - A. Poplawksi
- Department of Ophthalmology, University Medical Center, Johannes Gutenberg- University Mainz, Mainz, Germany
| | - N. Pfeiffer
- Department of Ophthalmology, University Medical Center, Johannes Gutenberg- University Mainz, Mainz, Germany
| | - E. M. Hoffmann
- Department of Ophthalmology, University Medical Center, Johannes Gutenberg- University Mainz, Mainz, Germany
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Holló G. Relationship between optical coherence tomography sector peripapillary angioflow-density and Octopus visual field cluster mean defect values. PLoS One 2017; 12:e0171541. [PMID: 28152106 PMCID: PMC5289610 DOI: 10.1371/journal.pone.0171541] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 01/17/2017] [Indexed: 11/18/2022] Open
Abstract
Purpose To compare the relationship of Octopus perimeter cluster mean-defect (cluster MD) values with the spatially corresponding optical coherence tomography (OCT) sector peripapillary angioflow vessel-density (PAFD) and sector retinal nerve fiber layer thickness (RNFLT) values. Methods High quality PAFD and RNFLT images acquired on the same day with the Angiovue/RTVue-XR Avanti OCT (Optovue Inc., Fremont, USA) on 1 eye of 27 stable early-to-moderate glaucoma, 22 medically controlled ocular hypertensive and 13 healthy participants were analyzed. Octopus G2 normal visual field test was made within 3 months from the imaging. Results Total peripapillary PAFD and RNFLT showed similar strong positive correlation with global mean sensitivity (r-values: 0.6710 and 0.6088, P<0.0001), and similar (P = 0.9614) strong negative correlation (r-values: -0.4462 and -0.4412, P≤0.004) with global MD. Both inferotemporal and superotemporal sector PAFD were significantly (≤0.039) lower in glaucoma than in the other groups. No significant difference between the corresponding inferotemporal and superotemporal parameters was seen. The coefficient of determination (R2) calculated for the relationship between inferotemporal sector PAFD and superotemporal cluster MD (0.5141, P<0.0001) was significantly greater than that between inferotemporal sector RNFLT and superotemporal cluster MD (0.2546, P = 0.0001). The R2 values calculated for the relationships between superotemporal sector PAFD and RNFLT, and inferotemporal cluster MD were similar (0.3747 and 0.4037, respectively, P<0.0001). Conclusion In the current population the relationship between inferotemporal sector PAFD and superotemporal cluster MD was strong. It was stronger than that between inferotemporal sector RNFLT and superotemporal cluster MD. Further investigations are necessary to clarify if our results are valid for other populations and can be usefully applied for glaucoma research.
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Affiliation(s)
- Gábor Holló
- Department of Ophthalmology, Semmelweis University, Budapest, Hungary
- * E-mail:
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20
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Pavlatos E, Perez BC, Morris HJ, Chen H, Palko JR, Pan X, Weber PA, Hart RT, Liu J. Three-Dimensional Strains in Human Posterior Sclera Using Ultrasound Speckle Tracking. J Biomech Eng 2016; 138:021015. [PMID: 26632258 DOI: 10.1115/1.4032124] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Indexed: 02/02/2023]
Abstract
Intraocular pressure (IOP) induced strains in the peripapillary sclera may play a role in glaucoma progression. Using inflation testing and ultrasound speckle tracking, the 3D strains in the peripapillary sclera were measured in nine human donor globes. Our results showed that the peripapillary sclera experienced through-thickness compression and meridional stretch during inflation, while minimal circumferential dilation was observed when IOP was increased from 10 to 19 mmHg. The maximum shear was primarily oriented in the through-thickness, meridional cross sections and had a magnitude slightly larger than the first principal strain. The tissue volume had minimal overall change, confirming near-incompressibility of the sclera. Substantial strain heterogeneity was present in the peripapillary region, with local high strain areas likely corresponding to structural heterogeneity caused by traversing blood vessels. These 3D strain characteristics provide new insights into the biomechanical responses of the peripapillary sclera during physiological increases of IOP. Future studies are needed to confirm these findings and investigate the role of these biomechanical characteristics in ocular diseases.
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Sawada Y, Hangai M, Ishikawa M, Yoshitomi T. Association of Myopic Optic Disc Deformation with Visual Field Defects in Paired Eyes with Open-Angle Glaucoma: A Cross-Sectional Study. PLoS One 2016; 11:e0161961. [PMID: 27571303 PMCID: PMC5003372 DOI: 10.1371/journal.pone.0161961] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 08/15/2016] [Indexed: 11/19/2022] Open
Abstract
PURPOSE To examine the association of myopia with the visual field (VF) defects in open-angle glaucoma (OAG) using paired eyes to eliminate the effect of unknown confounding factors that are diverse among individuals. METHODS One hundred eighteen eyes of 59 subjects with myopia (spherical equivalent [SE] ≥ -2 diopter [D] and axial length ≥ 24.0 mm) whose intra-ocular pressure between paired eyes was similar and the mean deviation (MD) of the Humphrey VF test differed by more than 6 dB were included. Refractive errors (SE, axial length) and parameters associated with the papillary and parapapillary myopic deformation (tilt ratio, torsion angle, and β-zone parapapillary atrophy [PPA] area without Bruch's membrane) were measured in each eye. The paired eyes were divided into worse and better eyes according to the MD of the VF, and parameters were compared between them. Further, multiple linear regression analysis was performed to examine the correlation of the difference in various parameters with the MD difference between paired eyes. RESULTS The SE of all eyes was -6.39 ± 2.15 D (mean ± standard deviation) and axial length was 26.42 ± 1.07 mm. MD of the worse and better VF eyes were -13.56 ± 6.65 dB and -4.87 ± 5.32 dB, respectively. Eyes with worse VFs had significantly greater SE, axial length, tilt ratio, and PPA area without Bruch's membrane than those with better VFs (all P < 0.05). In multiple linear regression analysis, the difference of the MD between paired eyes was significantly correlated with the difference in the tilt ratio and PPA area without Bruch's membrane. CONCLUSION The myopic papillary and parapapillary deformations, but not refractive error itself, were related to the worse VF in paired eyes with OAG. This suggests that myopia influences the severity of the glaucomatous VF defects via structural deformation.
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Affiliation(s)
- Yu Sawada
- Department of Ophthalmology, Akita University Graduate School of Medicine, Akita, Japan
| | - Masanori Hangai
- Department of Ophthalmology, Saitama Medical University, Saitama, Japan
| | - Makoto Ishikawa
- Department of Ophthalmology, Akita University Graduate School of Medicine, Akita, Japan
| | - Takeshi Yoshitomi
- Department of Ophthalmology, Akita University Graduate School of Medicine, Akita, Japan
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22
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Matsumoto CS, Shinoda K, Terauchi G, Matsumoto H, Mizota A, Miyake Y. Assessment of Macular Function during Vitrectomy: New Approach Using Intraoperative Focal Macular Electroretinograms. PLoS One 2015; 10:e0144627. [PMID: 26658489 PMCID: PMC4675556 DOI: 10.1371/journal.pone.0144627] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 11/21/2015] [Indexed: 11/22/2022] Open
Abstract
Purpose To describe a new technique to record focal macular electroretinograms (FMERGs) during vitrectomy to assess macular function. Methods Intraoperative FMERGs (iFMERGs) were recorded in ten patients (10 eyes) who undergo vitrectomy. iFMERGs were elicited by focal macular stimulation. The stimulus light was directed to the macular area through a 25 gauge (25G) glass fiber optic bundle. Background light was delivered through a dual chandelier-type light fiber probe. Focal macular responses elicited with combinations of stimulus and background luminances were analyzed. Results A stimulus luminance that was approximately 1.75 log units brighter than the background light was able to elicit focal macular responses that were not contaminated by stray light responses. Thus, a stimulus luminance of 160 cd/m2 delivered on a background of 3 cd/m2 elicited iFMEGs from only the stimulated area. This combination of stimulus and background luminances did not elicit a response when the stimulus was projected onto the optic nerve head. The iFMERGs elicited by a 10° stimulus with a duration of 100 ms and an interstimulus interval of 150 ms consisted of an a-, b-, and d-waves, the oscillatory potentials, and the photopic negative response (PhNR). Conclusions Focal ERGs with all components can be recorded from the macula and other retinal areas during vitreous surgery. This new technique will allow surgeons to assess the function of focal areas of the retina intraoperatively.
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Affiliation(s)
- Celso Soiti Matsumoto
- Department of Ophthalmology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo 173–8605, Japan
- Matsumoto Eye Clinic, Tokushima, Japan
| | - Kei Shinoda
- Department of Ophthalmology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo 173–8605, Japan
- * E-mail:
| | - Gaku Terauchi
- Department of Ophthalmology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo 173–8605, Japan
| | | | - Atsushi Mizota
- Department of Ophthalmology, Teikyo University School of Medicine, Kaga 2-11-1, Itabashi-ku, Tokyo 173–8605, Japan
| | - Yozo Miyake
- Aichi Medical University, 1–1 Yazakokarimata, Nagakute, Aichi, 480–1195, Japan
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23
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Abstract
The biomechanical environment within the eye is of interest in both the regulation of intraocular pressure and the loss of retinal ganglion cell axons in glaucomatous optic neuropathy. Unfortunately, this environment is complex and difficult to determine. Here we provide a brief introduction to basic concepts of mechanics (stress, strain, constitutive relationships) as applied to the eye, and then describe a variety of experimental and computational approaches used to study ocular biomechanics. These include finite element modeling, direct experimental measurements of tissue displacements using optical and other techniques, direct experimental measurement of tissue microstructure, and combinations thereof. Thanks to notable technical and conceptual advances in all of these areas, we are slowly gaining a better understanding of how tissue biomechanical properties in both the anterior and posterior segments may influence the development of, and risk for, glaucomatous optic neuropathy. Although many challenging research questions remain unanswered, the potential of this body of work is exciting; projects underway include the coupling of clinical imaging with biomechanical modeling to create new diagnostic tools, development of IOP control strategies based on improved understanding the mechanobiology of the outflow tract, and attempts to develop novel biomechanically-based therapeutic strategies for preservation of vision in glaucoma.
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Affiliation(s)
- Thao D Nguyen
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - C Ross Ethier
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, USA; Department of Mechanical Engineering, Georgia Institute of Technology, USA; Institute of Biosciences and Bioengineering, Georgia Institute of Technology, USA; Department of Ophthalmology, Emory University, USA.
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24
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Ayyalasomayajula A, Park RI, Simon BR, Geest JPV. A porohyperelastic finite element model of the eye: the influence of stiffness and permeability on intraocular pressure and optic nerve head biomechanics. Comput Methods Biomech Biomed Engin 2015; 19:591-602. [PMID: 26195024 PMCID: PMC4721930 DOI: 10.1080/10255842.2015.1052417] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Progressively deteriorating visual field is a characteristic feature of primary open-angle glaucoma (POAG), and the biomechanics of optic nerve head (ONH) is believed to be important in its onset. We used porohyperelasticity to model the complex porous behavior of ocular tissues to better understand the effect variations in ocular material properties can have on ONH biomechanics. An axisymmetric model of the human eye was constructed to parametrically study how changes in the permeabilities of retina-Bruch's-choroid complex (k(RBC)), sclera k(sclera), uveoscleral pathway (k(UVSC)) and trabecular meshwork k(TM) as well as how changes in the stiffness of the lamina cribrosa (LC) and sclera affect IOP, LC strains, and translaminar interstitial pressure gradients (TLIPG). Decreasing k(RBC) from 5 × 10(- 12) to 5 × 10(- 13) m/s increased IOP and LC strains by 17%, and TLIPG by 21%. LC strains increased by 13% and 9% when the scleral and LC moduli were decreased by 48% and 50%, respectively. In addition to the trabecular meshwork and uveoscleral pathway, the retina-Bruch's-choroid complex had an important effect on IOP, LC strains, and TLIPG. Changes in k(RBC) and scleral modulus resulted in nonlinear changes in the IOP, and LC strains especially at the lowest k(TM) and k(UVSC). This study demonstrates that porohyperelastic modeling provides a novel method for computationally studying the biomechanical environment of the ONH. Porohyperelastic simulations of ocular tissues may help provide further insight into the complex biomechanical environment of posterior ocular tissues in POAG.
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Affiliation(s)
| | | | - Bruce R. Simon
- Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ 85721
- Biomedical Engineering Graduate Interdisciplinary Program, University of Arizona, Tucson, AZ 85721
| | - Jonathan P. Vande Geest
- Department of Aerospace and Mechanical Engineering, University of Arizona, Tucson, AZ 85721
- Biomedical Engineering Graduate Interdisciplinary Program, University of Arizona, Tucson, AZ 85721
- Department of Biomedical Engineering, University of Arizona, Tucson, AZ 85721
- BIO5 Institute, University of Arizona, Tucson, AZ 85721
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25
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Pereira I, Weber S, Holzer S, Fischer G, Vass C, Resch H. Compensation for retinal vessel density reduces the variation of circumpapillary RNFL in healthy subjects. PLoS One 2015; 10:e0120378. [PMID: 25786232 PMCID: PMC4364727 DOI: 10.1371/journal.pone.0120378] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 02/06/2015] [Indexed: 11/18/2022] Open
Abstract
This work intends to assess circumpapillary retinal vessel density (RVD) at a 3.46 mm diameter circle and correlate it with circumpapillary retinal nerve fiber layer (RNFL) thickness measured with Fourier-Domain Optical Coherence Tomography. Furthermore, it aims to evaluate the reduction of intersubject variability of RNFL when considering RVD as a source of information for RNFL distribution. For that, 106 healthy subjects underwent circumpapillary RNFL measurement. Using the scanning laser ophthalmoscope fundus image, thickness and position of retinal vessels were assessed and integrated in a 256-sector RVD profile. The relationship between local RVD value and local RNFL thickness was modeled by linear regression. RNFL was then compensated for RVD variation by regression formulas. A strong statistically significant intrasubject correlation was found for all subjects between RVD and RNFL profiles (mean R = 0.769). In the intersubject regression analysis, 247 of 256 RNFL sectors showed a statistically significant positive correlation with RVD (mean R = 0.423). RVD compensation of RNFL resulted in a relative reduction of up to 20% of the intersubject variance. In conclusion, RVD in a 3.46 mm circle has a clinically relevant influence on the RNFL distribution. RVD may be used to develop more individualized normative values for RNFL measurement, which might improve early diagnosis of glaucoma.
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Affiliation(s)
- Ivania Pereira
- Center for Medical Statistics Informatics and Intelligent Systems, Section for Medical Information Management and Imaging, Medical University Vienna, Vienna, Austria
- Department of Ophthalmology & Optometry, Medical University Vienna, Vienna, Austria
| | - Stephanie Weber
- Department of Ophthalmology & Optometry, Medical University Vienna, Vienna, Austria
| | - Stephan Holzer
- Department of Ophthalmology & Optometry, Medical University Vienna, Vienna, Austria
| | - Georg Fischer
- Center for Medical Statistics Informatics and Intelligent Systems, Section for Medical Information Management and Imaging, Medical University Vienna, Vienna, Austria
| | - Clemens Vass
- Department of Ophthalmology & Optometry, Medical University Vienna, Vienna, Austria
| | - Hemma Resch
- Department of Ophthalmology & Optometry, Medical University Vienna, Vienna, Austria
- * E-mail:
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26
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Girard MJA, Dupps WJ, Baskaran M, Scarcelli G, Yun SH, Quigley HA, Sigal IA, Strouthidis NG. Translating ocular biomechanics into clinical practice: current state and future prospects. Curr Eye Res 2015; 40:1-18. [PMID: 24832392 PMCID: PMC4233020 DOI: 10.3109/02713683.2014.914543] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Biomechanics is the study of the relationship between forces and function in living organisms and is thought to play a critical role in a significant number of ophthalmic disorders. This is not surprising, as the eye is a pressure vessel that requires a delicate balance of forces to maintain its homeostasis. Over the past few decades, basic science research in ophthalmology mostly confirmed that ocular biomechanics could explain in part the mechanisms involved in almost all major ophthalmic disorders such as optic nerve head neuropathies, angle closure, ametropia, presbyopia, cataract, corneal pathologies, retinal detachment and macular degeneration. Translational biomechanics in ophthalmology, however, is still in its infancy. It is believed that its use could make significant advances in diagnosis and treatment. Several translational biomechanics strategies are already emerging, such as corneal stiffening for the treatment of keratoconus, and more are likely to follow. This review aims to cultivate the idea that biomechanics plays a major role in ophthalmology and that the clinical translation, lead by collaborative teams of clinicians and biomedical engineers, will benefit our patients. Specifically, recent advances and future prospects in corneal, iris, trabecular meshwork, crystalline lens, scleral and lamina cribrosa biomechanics are discussed.
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Affiliation(s)
- Michaël J A Girard
- In Vivo Biomechanics Laboratory, Department of Biomedical Engineering, National University of Singapore , Singapore
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27
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Pyne JD, Genovese K, Casaletto L, Vande Geest JP. Sequential-digital image correlation for mapping human posterior sclera and optic nerve head deformation. J Biomech Eng 2014; 136:021002. [PMID: 24337344 DOI: 10.1115/1.4026224] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Accepted: 12/12/2013] [Indexed: 01/26/2023]
Abstract
Optic nerve head (ONH) deformations may be involved in the onset or further development of glaucoma, including in patients with relatively normal intraocular pressures (IOPs). Characterizing posterior scleral deformations over physiological pressures may provide a better understanding of how changes in IOP lead to changes in the mechanical environment of the ONH and possibly retinal ganglion cell death. Pressure inflation measurement test protocols are commonly used to measure deformation of the peripapillary sclera with full-field noncontact optical methods. The purpose of this work was to develop and validate a new sequential 3D digital image correlation (S-DIC) approach for quantification of posterior scleral pressure induced deformation that improves z (in-depth) resolution of the DIC measurement without losing in-plane sensitivity, while also being able to contour and map deformations of the complex-shaped ONH. Our approach combines two orthogonal axes of parallax with standard 3D DIC methods using a single high-resolution camera. The enhanced capabilities of S-DIC with respect to standard 3D DIC has been demonstrated by carrying out a complete benchmark for shape, deformation, and strain measurement on an object of known complex geometry. Our S-DIC method provided a reconstruction accuracy of 0.17% and an uncertainty in z-position measurement of 8 μm. The developed methodology has also been applied to a human posterior scleral shell, including the full peripapillary sclera and optic nerve. The relatively inexpensive S-DIC approach may provide new information on the biomechanical deformations of the optic nerve head and, thus, the death of retinal ganglion cells in primary open angle glaucoma.
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Abstract
Optic disc measurements provide useful diagnostic information as they have correlations with certain eye diseases. In this paper, we provide an automatic method for detecting the optic disc in a single OCT slice. Our method is developed from the observation that the retinal pigment epithelium (RPE) which bounds the optic disc has a low-rank appearance structure that differs from areas within the disc. To detect the disc, our method acquires from the OCT image an RPE appearance model that is specific to the individual and imaging conditions, by learning a low-rank dictionary from image areas known to be part of the RPE according to priors on ocular anatomy. The edge of the RPE, where the optic disc is located, is then found by traversing the retinal layer containing the RPE, reconstructing local appearance with the low-rank model, and detecting the point at which appearance starts to deviate (i.e., increased reconstruction error). To aid in this detection, we also introduce a geometrical constraint called the distance bias that accounts for the smooth shape of the RPE. Experiments demonstrate that our method outperforms other OCT techniques in localizing the optic disc and estimating disc width. Moreover, we also show the potential usage of our method on optic disc area detection in 3-D OCT volumes.
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29
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Sigal IA, Grimm JL, Schuman JS, Kagemann L, Ishikawa H, Wollstein G. A method to estimate biomechanics and mechanical properties of optic nerve head tissues from parameters measurable using optical coherence tomography. IEEE Trans Med Imaging 2014; 33:1381-1389. [PMID: 24691117 PMCID: PMC5544498 DOI: 10.1109/tmi.2014.2312133] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Optic nerve head (ONH) tissue properties and biomechanics remain mostly unmeasurable in the experiment. We hypothesized that these can be estimated numerically from ocular parameters measurable in vivo with optical coherence tomography (OCT). Using parametric models representing human ONHs we simulated acute intraocular pressure (IOP) increases (10 mmHg). Statistical models were fit to predict, from OCT-measurable parameters, 15 outputs, including ONH tissue properties, stresses, and deformations. The calculations were repeated adding parameters that have recently been proposed as potentially measurable with OCT. We evaluated the sensitivity of the predictions to variations in the experimental parameters. Excellent fits were obtained to predict all outputs from the experimental parameters, with cross-validated R2s between 0.957 and 0.998. Incorporating the potentially measurable parameters improved fits significantly. Predictions of tissue stiffness were accurate to within 0.66 MPa for the sclera and 0.24 MPa for the lamina cribrosa. Predictions of strains and stresses were accurate to within 0.62% and 4.9 kPa, respectively. Estimates of ONH biomechanics and tissue properties can be obtained quickly from OCT measurements using an applet that we make freely available. These estimates may improve understanding of the eye sensitivity to IOP and assessment of patient risk for development or progression of glaucoma.
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Affiliation(s)
| | - J. L. Grimm
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA 15213 USA
| | - J. S. Schuman
- Departments of Ophthalmology and Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213 USA, and also with the McGowan Institute for Regenerative Science, Pittsburgh, PA 15219 USA, and also with the Fox Center for Vision Restoration, University of Pittsburgh Medical Center and the University of Pittsburgh, Pittsburgh, PA 15213 USA
| | - L. Kagemann
- Departments of Ophthalmology and Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213 USA
| | - H. Ishikawa
- Departments of Ophthalmology and Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213 USA
| | - G. Wollstein
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA 15213 USA, and also with the Fox Center for Vision Restoration, University of Pittsburgh Medical Center, and the University of Pittsburgh, Pittsburgh, PA 15213 USA
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30
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Welikala RA, Dehmeshki J, Hoppe A, Tah V, Mann S, Williamson TH, Barman SA. Automated detection of proliferative diabetic retinopathy using a modified line operator and dual classification. Comput Methods Programs Biomed 2014; 114:247-261. [PMID: 24636803 DOI: 10.1016/j.cmpb.2014.02.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 01/14/2014] [Accepted: 02/14/2014] [Indexed: 06/03/2023]
Abstract
Proliferative diabetic retinopathy (PDR) is a condition that carries a high risk of severe visual impairment. The hallmark of PDR is neovascularisation, the growth of abnormal new vessels. This paper describes an automated method for the detection of new vessels in retinal images. Two vessel segmentation approaches are applied, using the standard line operator and a novel modified line operator. The latter is designed to reduce false responses to non-vessel edges. Both generated binary vessel maps hold vital information which must be processed separately. This is achieved with a dual classification system. Local morphology features are measured from each binary vessel map to produce two separate feature sets. Independent classification is performed for each feature set using a support vector machine (SVM) classifier. The system then combines these individual classification outcomes to produce a final decision. Sensitivity and specificity results using a dataset of 60 images are 0.862 and 0.944 respectively on a per patch basis and 1.00 and 0.90 respectively on a per image basis.
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Affiliation(s)
- R A Welikala
- Digital Imaging Research Centre, Faculty of Science, Engineering and Computing, Kingston University, London, United Kingdom.
| | - J Dehmeshki
- Digital Imaging Research Centre, Faculty of Science, Engineering and Computing, Kingston University, London, United Kingdom
| | - A Hoppe
- Digital Imaging Research Centre, Faculty of Science, Engineering and Computing, Kingston University, London, United Kingdom
| | - V Tah
- Medical Retina, Oxford Eye Hospital, Oxford, United Kingdom
| | - S Mann
- Ophthalmology Department, St. Thomas' Hospital, London, United Kingdom
| | - T H Williamson
- Ophthalmology Department, St. Thomas' Hospital, London, United Kingdom
| | - S A Barman
- Digital Imaging Research Centre, Faculty of Science, Engineering and Computing, Kingston University, London, United Kingdom
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31
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Geiser MH, Truffer F, Evequoz H, Khayi H, Mottet B, Chiquet C. Schlieren laser Doppler flowmeter for the human optical nerve head with the flicker stimuli. J Biomed Opt 2013; 18:127001. [PMID: 24296999 DOI: 10.1117/1.jbo.18.12.127001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 10/30/2013] [Indexed: 06/02/2023]
Abstract
We describe a device to measure blood perfusion for the human optic nerve head (ONH) based on laser Doppler flowmetry (LDF) with a flicker stimuli of the fovea region. This device is self-aligned for LDF measurements and includes near-infrared pupil observation, green illumination, and observation of the ONH. The optical system of the flowmeter is based on a Schlieren arrangement which collects only photons that encounter multiple scattering and are back-scattered out of the illumination point. LDF measurements are based on heterodyne detection of Doppler shifted back-scattered light. We also describe an automated analysis of the LDF signals which rejects artifacts and false signals such as blinks. By using a Doppler simulator consisting of a lens and a rotating diffusing wheel, we demonstrate that velocity and flow vary linearly with the speed of the wheel. A cohort of 12 healthy subjects demonstrated that flicker stimulation induces an increase of 17.8% of blood flow in the ONH.
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Affiliation(s)
- Martial H Geiser
- University of Applied Sciences Western Switzerland, Institute of Systems Engineering, Sion 1950, Switzerland
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Coudrillier B, Boote C, Quigley HA, Nguyen TD. Scleral anisotropy and its effects on the mechanical response of the optic nerve head. Biomech Model Mechanobiol 2013; 12:941-63. [PMID: 23188256 PMCID: PMC3615129 DOI: 10.1007/s10237-012-0455-y] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 11/05/2012] [Indexed: 10/27/2022]
Abstract
This paper presents a computational modeling study of the effects of the collagen fiber structure on the mechanical response of the sclera and the adjacent optic nerve head (ONH). A specimen-specific inverse finite element method was developed to determine the material properties of two human sclera subjected to full-field inflation experiments. A distributed fiber model was applied to describe the anisotropic elastic behavior of the sclera. The model directly incorporated wide-angle X-ray scattering measurements of the anisotropic collagen structure. The converged solution of the inverse method was used in micromechanical studies of the mechanical anisotropy of the sclera at different scales. The effects of the scleral collagen fiber structure on the ONH deformation were evaluated by progressively filtering out local anisotropic features. It was found that the majority of the midposterior sclera could be described as isotropic without significantly affecting the mechanical response of the tissues of the ONH. In contrast, removing local anisotropic features in the peripapillary sclera produced significant changes in scleral canal expansion and lamina cribrosa deformation. Local variations in the collagen structure of the peripapillary sclera significantly influenced the mechanical response of the ONH.
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Affiliation(s)
- Baptiste Coudrillier
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA,
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Abstract
Retinal ganglion cells (RGCs), the output neurons of the retina, have axons that project via the optic nerve to diverse targets in the brain. Typically, RGC axons do not branch before exiting the retina and thus do not provide it with synaptic feedback. Although a small subset of RGCs with intraretinal axon collaterals has been previously observed in human, monkey, cat, and turtle, their function remains unknown. A small, more recently identified population of RGCs expresses the photopigment melanopsin. These intrinsically photosensitive retinal ganglion cells (ipRGCs) transmit an irradiance-coding signal to visual nuclei in the brain, contributing both to image-forming vision and to several nonimage-forming functions, including circadian photoentrainment and the pupillary light reflex. In this study, using melanopsin immunolabeling in monkey and a genetic method to sparsely label the melanopsin cells in mouse, we show that a subgroup of ipRGCs have axons that branch en route to the optic disc, forming intraretinal axon collaterals that terminate in the inner plexiform layer of the retina. The previously described collateral-bearing population identified by intracellular dye injection is anatomically indistinguishable from the collateral-bearing melanopsin cells identified here, suggesting they are a subset of the melanopsin-expressing RGC type and may therefore share its functional properties. Identification of an anatomically distinct subpopulation in mouse, monkey, and human suggests this pathway may be conserved in these and other species (turtle and cat) with intraretinal axon collaterals. We speculate that ipRGC axon collaterals constitute a likely synaptic pathway for feedback of an irradiance signal to modulate retinal light responses.
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Affiliation(s)
- Hannah R. Joo
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218
- Department of Biological Structure and the National Primate Research Center, University of Washington, Seattle, WA 98195
| | - Beth B. Peterson
- Department of Biological Structure and the National Primate Research Center, University of Washington, Seattle, WA 98195
| | - Dennis M. Dacey
- Department of Biological Structure and the National Primate Research Center, University of Washington, Seattle, WA 98195
| | - Samer Hattar
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218
- Department of Neuroscience, Johns Hopkins University, Baltimore, MD 21218
| | - Shih-Kuo Chen
- Department of Biology, Johns Hopkins University, Baltimore, MD 21218
- Department of Zoology, National Taiwan University, Taipei, Taiwan 106
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Shahbeig S, Pourghassem H. Fast and automatic algorithm for optic disc extraction in retinal images using principle-component-analysis-based preprocessing and curvelet transform. J Opt Soc Am A Opt Image Sci Vis 2013; 30:13-21. [PMID: 23455998 DOI: 10.1364/josaa.30.000013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Optic disc or optic nerve (ON) head extraction in retinal images has widespread applications in retinal disease diagnosis and human identification in biometric systems. This paper introduces a fast and automatic algorithm for detecting and extracting the ON region accurately from the retinal images without the use of the blood-vessel information. In this algorithm, to compensate for the destructive changes of the illumination and also enhance the contrast of the retinal images, we estimate the illumination of background and apply an adaptive correction function on the curvelet transform coefficients of retinal images. In other words, we eliminate the fault factors and pave the way to extract the ON region exactly. Then, we detect the ON region from retinal images using the morphology operators based on geodesic conversions, by applying a proper adaptive correction function on the reconstructed image's curvelet transform coefficients and a novel powerful criterion. Finally, using a local thresholding on the detected area of the retinal images, we extract the ON region. The proposed algorithm is evaluated on available images of DRIVE and STARE databases. The experimental results indicate that the proposed algorithm obtains an accuracy rate of 100% and 97.53% for the ON extractions on DRIVE and STARE databases, respectively.
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Affiliation(s)
- Saleh Shahbeig
- Department of Electrical Engineering, Najafabad Branch, Islamic Azad University, 517, Najafabad, Isfahan, Iran
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35
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Abstract
Coloboma is a congenital disease that contributes significantly to childhood blindness. It results from the failure in closing the optic fissure, a transient opening on the ventral side of the developing eye. Although human and mouse genetic studies have identified a number of genes associated with coloboma, the detailed cellular mechanisms underlying the optic fissure closure and coloboma formation remain largely undefined. N-cadherin-mediated cell adhesion has been shown to be important for the optic fissure closure in zebrafish, but it remains to be determined experimentally how cell-cell adhesions are involved in the mammalian optic fissure closing process. α-catenin is required for cell adhesion mediated by all of the classic cadherin molecules, including N-cadherin. In this study, we used the Cre-mediated conditional knockout technique to specifically delete α-catenin from the developing mouse eye to show that it is required for the successful closing of the optic fissure. In α-catenin conditional mutant optic cups, the major cell fates, including the optic fissure margin, neural retina and retinal pigmented epithelium, are specified normally, and the retinal progenitor cells proliferate normally. However, adherens junctions components, including N-cadherin, β-catenin and filamentous actin, fail to accumulate on the apical side of α-catenin mutant retinal progenitor cells, where adherens junctions are normally abundant, and the organization of the neural retina and the optic fissure margin is disrupted. Finally, the α-catenin mutant retina gradually degenerates in the adult mouse eye. Therefore, our results show that α-catenin-mediated cell adhesion and cell organization are important for the fissure closure in mice, and further suggest that genes that regulate cell adhesion may underlie certain coloboma cases in humans.
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Affiliation(s)
- Shuyi Chen
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- * E-mail: (SC); (TX)
| | - Brandy Lewis
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Andrea Moran
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - Ting Xie
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- Department of Cell Biology and Anatomy, University of Kansas Medical Center, Kansas City, Kansas, United States of America
- * E-mail: (SC); (TX)
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An L, Johnstone M, Wang RK. Optical microangiography provides correlation between microstructure and microvasculature of optic nerve head in human subjects. J Biomed Opt 2012; 17:116018. [PMID: 23128971 PMCID: PMC3595642 DOI: 10.1117/1.jbo.17.11.116018] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 10/07/2012] [Accepted: 10/09/2012] [Indexed: 06/01/2023]
Abstract
It is demonstrated that optical microangiography (OMAG) is capable of imaging the detailed microstructure and microvasculature of the in vivo human optic nerve head (ONH), including the prelaminar tissue, the lamina cribrosa, the scleral rim and the vessels in the region of the circle of Zin-Haller. For demonstration, an ultrahigh sensitive OMAG system operating in the 850 nm wavelength region and a 500 kHz A-scan rate resulting in a spatial resolution of ∼6 μm were used. It was shown that OMAG provides superior results for three-dimensional imaging of the ONH compared to conventional optical coherence tomography by simultaneously recording both the microstructure and the functional microcirculation. The blood supply to the tissues of the ONH is an essential physiologic parameter needed for clinical assessment of the health of the nerve.
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Affiliation(s)
- Lin An
- University of Washington, Departments of Bioengineering, Seattle, Washington 98195
| | - Murray Johnstone
- University of Washington, Department of Ophthalmology, Seattle, Washington 98104
| | - Ruikang K. Wang
- University of Washington, Departments of Bioengineering, Seattle, Washington 98195
- University of Washington, Department of Ophthalmology, Seattle, Washington 98104
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37
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Abstract
Neural transmission latency would introduce a spatial lag when an object moves across the visual field, if the latency was not compensated. A visual predictive mechanism has been proposed, which overcomes such spatial lag by extrapolating the position of the moving object forward. However, a forward position shift is often absent if the object abruptly stops moving (motion-termination). A recent "correction-for-extrapolation" hypothesis suggests that the absence of forward shifts is caused by sensory signals representing 'failed' predictions. Thus far, this hypothesis has been tested only for extra-foveal retinal locations. We tested this hypothesis using two foveal scotomas: scotoma to dim light and scotoma to blue light. We found that the perceived position of a dim dot is extrapolated into the fovea during motion-termination. Next, we compared the perceived position shifts of a blue versus a green moving dot. As predicted the extrapolation at motion-termination was only found with the blue moving dot. The results provide new evidence for the correction-for-extrapolation hypothesis for the region with highest spatial acuity, the fovea.
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Affiliation(s)
- Zhuanghua Shi
- Department Psychologie, Ludwig-Maximilians-Universität München, Munich, Germany.
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Abstract
PURPOSE A method is presented for the calculation and visualization of percent blood oxygen saturation from specific tissue structures in hyperspectral images of the optic nerve head (ONH). METHODS Trans-pupillary images of the primate optic nerve head and overlying retinal blood vessels were obtained with a hyperspectral imaging (HSI) system attached to a fundus camera. Images were recorded during normal blood flow and after partially interrupting flow to the ONH and retinal circulation by elevation of the intraocular pressure (IOP) from 10 mmHg to 55 mmHg in steps. Percent oxygen saturation was calculated from groups of pixels associated with separate tissue structures, using a linear least-squares curve fit of the recorded hemoglobin spectrum to reference spectra obtained from fully oxygenated and deoxygenated red cell suspensions. Color maps of saturation were obtained from a new algorithm that enables comparison of oxygen saturation from large vessels and tissue areas in hyperspectral images. RESULTS Percent saturation in retinal vessels and from the average over ONH structures (IOP = 10 mmHg) was (mean +/- SE): artery 81.8 +/- 0.4%, vein 42.6 +/- 0.9%, average ONH 68.3 +/- 0.4%. Raising IOP from 10 mmHg to 55 mmHg for 5 min caused blood oxygen saturation to decrease (mean +/- SE): artery 46.1 +/- 6.2%, vein 36.1 +/- 1.6%, average ONH 41.9 +/- 1.6%. The temporal cup showed the highest saturation at low and high IOP (77.3 +/- 1.0% and 60.1 +/- 4.0%) and the least reduction in saturation at high IOP (22.3%) compared with that of the average ONH (38.6%). A linear relationship was found between saturation indices obtained from the algorithm and percent saturation values obtained by spectral curve fits to calibrated red cell samples. CONCLUSIONS Percent oxygen saturation was determined from hyperspectral images of the ONH tissue and retinal vessels overlying the ONH at normal and elevated IOP. Pressure elevation was shown to reduce blood oxygen saturation in vessels and ONH structures, with the smallest reduction in the ONH observed in the temporal cup. IOP-induced saturation changes were visualized in color maps using an algorithm that follows saturation-dependent changes in the blood spectrum and blood volume differences across tissue. Reduced arterial saturation at high IOP may have resulted from a flow-dependent mechanism.
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Affiliation(s)
- James Beach
- Institute for Technology Development, Stennis Space Center, Bay St. Louis, Mississippi, USA.
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Agopov M, Lomb L, La Schiazza O, Bille JF. Second harmonic generation imaging of the pig lamina cribrosa using a scanning laser ophthalmoscope-based microscope. Lasers Med Sci 2009; 24:787-92. [PMID: 19224333 DOI: 10.1007/s10103-008-0641-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 12/23/2008] [Indexed: 10/21/2022]
Abstract
We describe a novel scanning laser ophthalmoscope (SLO)-based on a video-rate second harmonic generation imaging microscope. A titanium:sapphire femtosecond laser was coupled to a modified SLO. The laser beam was scanned over the sample, and the light produced by second harmonic generation (SHG) was collected for imaging at video-speed. The device was used for imaging the lamina cribrosa (LC) of enucleated pig eyes. A resolution comparable to that of commercial multiphoton microscopes was reached. The SHG images were used for determining the average pore size of the LC determined from the images; the pressure dependence of the pore size was studied by the artificial increasing of the hydrostatic pressure in the eye. A pressure increase of 44.3 mmHg enlarged the average pore size of 62 analyzed pores by a statistically significant amount. The relative pore growth was measured at four different pressure levels in 25 pores. The pressure was increased in 15 mmHg steps. A general tendency for monothonic growth was observed, although single pores grew by no means linearly.
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Affiliation(s)
- M Agopov
- Kirchhoff-Institut für Physik, INF 227, Heidelberg, Germany.
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40
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Lim L, Gazzard G, Chan YH, Fong A, Kotecha A, Sim EL, Tan D, Tong L, Saw SM. Corneal biomechanics, thickness and optic disc morphology in children with optic disc tilt. Br J Ophthalmol 2008; 92:1461-6. [PMID: 18703551 DOI: 10.1136/bjo.2008.139113] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- L Lim
- Singapore Eye Research Institute, Singapore
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Ruangvaravate N, Neungton C. Normative data of optic nerve head in Thai population by laser scanning tomography: Siriraj study. J Med Assoc Thai 2008; 91:859-863. [PMID: 18697385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
OBJECTIVE To study the normative values of topographic optic disc parameters in a Thai population. MATERIAL AND METHOD Two hundred and six eyes of 103 normal subjects aging from 30-80 years were studied Thirteen topographic disc parameters were analyzed by confocal scanning laser ophthalmoscope using Heidelburg retina tomography (HRT II). The average value of two eyes in the same subject was used as the unit of statistical analysis, and then the normal values and means were statistically calculated at 95% reference interval (95% RI). Ethnic differences of the calculated optic nerve topography were compared with previous studies. The relationship of age, intraocular pressure (IOP), central corneal thickness (CCT), and optic disc parameters were assessed by Pearson correlation. RESULTS Mean values with 95% RI of all 13 parameters were analyzed Whole parameters except cup volume demonstrated normal distribution. Mean value (95% RI) of disc area in normal Thai people was 2.67 mm2 (1.96, 3.71) which was larger than Caucasian people. Ethnic differences in topographic optic disc parameters were found among Thai and other races including Asians, Caucasians, African-Americans, and Hispanics. The results also revealed that age, IOP, and CCT had no significant relation to all optic disc parameters. CONCLUSION Thai people had a larger optic disc area than Caucasians. There are marked differences of topographic optic nerve parameters among different ethnic groups. These differences need to be taken into account when evaluating glaucomatous optic neuropathy and when comparing results of studies completed among population of different ethnic and racial origins.
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Affiliation(s)
- Ngamkae Ruangvaravate
- Department of Ophthalmology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
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42
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Abstract
Our visual percepts are not fully determined by the physical stimulus input. That is why we perceive crisp bounding contours even in the absence of luminance-defined borders in visual illusions such as the Kanizsa figure. It is important to understand which neural processes are involved in creating these artificial visual experiences because this might tell us how we perceive coherent objects in natural scenes, which are characterized by mutual overlap. We have already shown using functional magnetic resonance imaging [Maertens, M., & Pollmann, S. fMRI reveals a common neural substrate of illusory and real contours in v1 after perceptual learning. Journal of Cognitive Neuroscience, 17, 1553-1564, 2005] that neurons in the primary visual cortex (V1) respond to these stimuli. Here we provide support for the hypothesis that V1 is obligatory for the discrimination of the curvature of illusory contours. We presented illusory contours across the portion of the visual field corresponding to the physiological "blind spot." Four observers were extensively trained and asked to discriminate fine curvature differences in these illusory contours. A distinct performance drop (increased errors and response latencies) was observed when illusory contours traversed the blind spot compared to when they were presented in the "normal" contralateral visual field at the same eccentricity. We attribute this specific performance deficit to the failure to build up a representation of the illusory contour in the absence of a cortical representation of the "blind spot" within V1. The current results substantiate the assumption that neural activity in area V1 is closely related to our phenomenal experience of illusory contours in particular, and to the construction of our subjective percepts in general.
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Abstract
The biomechanics of the optic nerve head (ONH) may underlie many of the potential mechanisms that initiate the characteristic vision loss associated with primary open angle glaucoma. Therefore, it is important to characterize the physiological levels of stress and strain in the ONH and how they may change in relation to material properties, geometry, and microstructure of the tissue. An idealized, analytical microstructural model of the ONH load bearing tissues was developed based on an octagonal cellular solid that matched the porosity and pore area of morphological data from the lamina cribrosa (LC). A complex variable method for plane stress was applied to relate the geometrically dependent macroscale loads in the sclera to the microstructure of the LC, and the effect of different geometric parameters, including scleral canal eccentricity and laminar and scleral thickness, was examined. The transmission of macroscale load in the LC to the laminar microstructure resulted in stress amplifications between 2.8 and 24.5xIOP. The most important determinants of the LC strain were those properties pertaining to the sclera and included Young's modulus, thickness, and scleral canal eccentricity. Much larger strains were developed perpendicular to the major axis of an elliptical canal than in a circular canal. Average strain levels as high as 5% were obtained for an increase in IOP from 15 to 50 mm Hg.
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Affiliation(s)
- E A Sander
- School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA
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Woo YM, Lee MS, Nam Y, Cho HJ, Shin BC. Effects of contralateral electroacupuncture on brain function: a double-blind, randomized, pilot clinical trial. J Altern Complement Med 2007; 12:813-5. [PMID: 17034288 DOI: 10.1089/acm.2006.12.813] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES The aim of this study was to ascertain the effects of contralateral acupuncture on brain function using blind-spot mapping. DESIGN AND PARTICIPANTS Forty (40) healthy volunteers in whom the right-side blind spot was larger than the left-side one-which indicates lower left-brain function-were randomly assigned into the following two groups in which electroacupuncture was applied to: (1) the contralateral ST36 acupuncture point (right side), and (2) the ipsilateral ST36 acupuncture point (left side). OUTCOME MEASURE Blind-spot perimetry length was the outcome measure. RESULTS Electroacupuncture to the contralateral side decreased the blind-spot perimetry length by 5.0 (-9.3 to 0.9) [median (interquartile range, IQR)], whereas that to the ipsilateral side increased the length by 4.5 (-3.7 to 7.8) [median, IQR]. There was significant difference in this length between the two groups (p < 0.05). CONCLUSIONS These results suggest that electroacupuncture application increased or decreased the brain function- as assessed by changes to the blind spot-depending on the treatment side: Contralateral-side treatment has a better effect than ipsilateral-side treatment on brain function. However, further randomized studies that include both right- and left-side-enlarged subjects with a sham needle are needed to convincingly show the effects of contralateral acupuncture on brain function.
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Affiliation(s)
- Young-Min Woo
- Department of Acupuncture and Moxibustion, National Medical Center, Seoul, Republic of Korea
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Abstract
A retinal ganglion cell density map was generated using Nissl-stained retinal whole mounts from the jungle crow (Corvus macrorhynchos). The total number, distribution and size of these cells were determined in the area centralis, as well as in temporal, nasal, dorsal and ventral retinal regions. The mean total number of ganglion cells was estimated to be 3.6 x 10(6). The highest densities were found in the area centralis (25 600 /mm2) and the dorso-temporal part of the retina, suggesting the highest quality of vision. This density diminished nearly concentrically from the central area towards the retinal periphery. The number of ganglion cells was highest in the temporal retina followed, in order, by the nasal, dorsal and ventral retinal regions. Based on ganglion cell size, the retina seemed to consist of the following five regions: central, temporal, nasal, dorsal and ventral. Ganglion cell size ranged from 16 to 288 microm2, with smaller cells predominating in central regions above the optic disc and larger cells comprising more of the peripheral regions. The present study showed two highly populated areas of ganglion cells in the crow retina and it is expected that the crow retina provides well-developed monocular and binocular vision.
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Affiliation(s)
- Mohammad Lutfur Rahman
- Department of Animal Science, Faculty of Agriculture, Utsunomiya University, Utsunomiya, Japan
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Dolderer J, Vonthein R, Johnson CA, Schiefer U, Hart W. Scotoma mapping by semi-automated kinetic perimetry: the effects of stimulus properties and the speed of subjects' responses. ACTA ACUST UNITED AC 2006; 84:338-44. [PMID: 16704695 DOI: 10.1111/j.1600-0420.2005.00624.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE The study aimed firstly to determine the effects of stimulus variables on the detection of a scotoma border and, secondly, to study the reproducibility of the method during semi-automated kinetic perimetry. METHODS The size of the physiological blind spot in 18 young normal subjects was measured with a video-campimetric device, the Tübingen computer campimeter (TCC). Kinetic stimuli of two different sizes and at four different levels of luminance were presented. Examinations were repeated within 2 weeks. Measurements were corrected for individual response times and the area of the blind spot was computed. The effects of stimulus strength and size and the repeatability of blind spot measurements were evaluated by an analysis of variance. RESULTS The physiological blind spot showed significant inter- and intraindividual variations in size (least square means ranging from 17 to 49 square degrees), with a standard deviation of 6.8 square degrees. The measured size of the blind spot increased as a function of decreasing stimulus value, by reducing either the relative brightness or the size of stimuli. Use of a correction for each subject's speed of responses nearly halved the level of random variance. The temporal sequence of measurements (the order in which they were performed) had no apparent effect on the calculated values of blind spot size. CONCLUSIONS Semi-automated kinetic perimetry can determine the size of the physiological blind spot with good repeatability in young, normal subjects. Determination of each individual's speed of response and inclusion of this variable in the calculations reduced variance of the measure significantly. This study confirmed the presence of considerable interindividual differences in the size of the physiological blind spot.
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Affiliation(s)
- Jan Dolderer
- Department of Pathophysiology of Vision and Neuro-Ophthalmology, University Eye Hospital, Tübingen, Germany
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Abstract
PURPOSE The biomechanical environment within the optic nerve head (ONH) may play a role in retinal ganglion cell loss in glaucomatous optic neuropathy. This was a systematic analysis in which finite element methods were used to determine which anatomic and biomechanical factors most influenced the biomechanical response of the ONH to acute changes in IOP. METHODS Based on a previously described computational model of the eye, each of 21 input factors, representing the biomechanical properties of relevant ocular tissues, the IOP, and 14 geometric factors were independently varied. The biomechanical response of the ONH tissues was quantified through a set of 29 outcome measures, including peak and mean stress and strain within each tissue, and measures of geometric changes in ONH tissues. Input factors were ranked according to their aggregated influence on groups of outcome measures. RESULTS The five input factors that had the largest influence across all outcome measures were, in ranked order: stiffness of the sclera, radius of the eye, stiffness of the lamina cribrosa, IOP, and thickness of the scleral shell. The five least influential factors were, in reverse ranked order: retinal thickness, peripapillary rim height, cup depth, cup-to-disc ratio, and pial thickness. Factor ranks were similar for various outcome measure groups and factor ranges. CONCLUSIONS The model predicts that ONH biomechanics are strongly dependent on scleral biomechanical properties. Acute deformations of ONH tissues, and the consequent high levels of neural tissue strain, were less strongly dependent on the action of IOP directly on the internal surface of the ONH than on the indirect effects of IOP on the sclera. This suggests that interindividual variations in scleral properties could be a risk factor for the development of glaucoma. Eye size and lamina cribrosa biomechanical properties also have a strong influence on ONH biomechanics.
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Affiliation(s)
- Ian A Sigal
- Department of Mechanical and Industrial Engineering, University of Toronto, Ontario, Canada
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Abstract
Axon guidance is one of the critical processes during vertebrate central nervous system (CNS) development. The optic nerve, which contains the axons of retinal ganglion cells, has been used as a powerful model to elucidate some of the mechanisms underlying axon guidance because it is easily manipulated experimentally, and its function is well understood. Recent molecular biology studies have revealed that numerous guidance molecules control the development of the visual pathway. This review introduces the molecular mechanisms involved in each critical step during optic axon guidance. Axonal projections to the optic disc are thought to depend on adhesion molecules and inhibitory extracellular matrices such as chondroitin sulfate. The formation of the head of the optic nerve and the optic chiasm require ligand-receptor interactions between netrin-1 and the deleted in colorectal cancer receptor, and Slit proteins and Robo receptors, respectively. The gradient distributions of ephrin ligands and Eph receptors are essential for correct ipsilateral projections at the optic chiasm and the topographic mapping of axons in the superior colliculus/optic tectum. The precise gradient is regulated by transcription factors determining the retinal dorso-ventral and nasal-temporal polarities. Moreover, the axon guidance activities by Slit and semaphorin 5A require the existence of heparan sulfate, which binds to numerous guidance molecules. Recent discoveries about the molecular mechanisms underlying optic nerve guidance will facilitate progress in CNS developmental biology and axon-regeneration therapy.
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Affiliation(s)
- Masaru Inatani
- Department of Ophthalmology and Visual Science, Kumamoto University Graduate School of Medical Sciences, 1-1-1 Honjo, Kumamoto 860-8556, Japan.
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Abstract
The neural mechanism that mediates perceptual filling-in of the blind spot is still under discussion. One hypothesis proposes that the cortical representation of the blind spot is activated only under conditions that elicit perceptual filling-in and requires congruent stimulation on both sides of the blind spot. Alternatively, the passive remapping hypothesis proposes that inputs from regions surrounding the blind spot infiltrate the representation of the blind spot in cortex. This theory predicts that independent stimuli presented to the left and right of the blind spot should lead to neighboring/overlapping activations in visual cortex when the blind-spot eye is stimulated but separated activations when the fellow eye is stimulated. Using functional MRI, we directly tested the remapping hypothesis by presenting flickering checkerboard wedges to the left or right of the spatial location of the blind spot, either to the blind-spot eye or to the fellow eye. Irrespective of which eye was stimulated, we found separate activations corresponding to the left and right wedges. We identified the centroid of the activations on a cortical flat map and measured the distance between activations. Distance measures of the cortical gap across the blind spot were accurate and reliable (mean distance: 6-8 mm across subjects, SD approximately 1 mm within subjects). Contrary to the predictions of the remapping hypothesis, cortical distances between activations to the two wedges were equally large for the blind-spot eye and fellow eye in areas V1 and V2/V3. Remapping therefore appears unlikely to account for perceptual filling-in at an early cortical level.
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Affiliation(s)
- Holger Awater
- Princeton University, Dept. of Psychology, Green Hall, Princeton, NJ, 08544
- *Corresponding authors: Holger Awater, Vanderbilt University, Dept. of Psychology, 301 Wilson Hall, Nashville, TN, 37203, USA, Phone: 615 - 322 – 2835, E-mail:, Frank Tong, Vanderbilt University, Dept. of Psychology, 301 Wilson Hall, Nashville, TN, 37203, USA, Phone: 615 - 322 – 1780, E-mail:
| | - Jess R. Kerlin
- Princeton University, Dept. of Psychology, Green Hall, Princeton, NJ, 08544
| | - Karla K. Evans
- Princeton University, Dept. of Psychology, Green Hall, Princeton, NJ, 08544
| | - Frank Tong
- Princeton University, Dept. of Psychology, Green Hall, Princeton, NJ, 08544
- *Corresponding authors: Holger Awater, Vanderbilt University, Dept. of Psychology, 301 Wilson Hall, Nashville, TN, 37203, USA, Phone: 615 - 322 – 2835, E-mail:, Frank Tong, Vanderbilt University, Dept. of Psychology, 301 Wilson Hall, Nashville, TN, 37203, USA, Phone: 615 - 322 – 1780, E-mail:
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Volkov VV. [Ocular structural and functional disturbances, typical for open-angle glaucoma, are the basis for the development of its present-day classification]. Vestn Oftalmol 2005; 121:35-9. [PMID: 16223043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
A major breakthrough in the development of clinical studies of the structures and functions of the optic disk (OD) has allowed one to notice the earliest manifestations of open-angle glaucoma (OAG). Along with this, consideration of the data accumulated in the literature on the role of risk factors of glaucoma and on the variants of the clinical course of the disease has enabled the author to suggest to update the OAG classification developed 30 years ago. The proposed schemes use just the procedures currently recommended by the International Glaucoma Association as the most informative ones.
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