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Song D, Lim S, Park J, Demer JL. Linear viscoelasticity of human sclera and posterior ocular tissues during tensile creep. J Biomech 2023; 151:111530. [PMID: 36933327 PMCID: PMC11407690 DOI: 10.1016/j.jbiomech.2023.111530] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 02/21/2023] [Accepted: 03/02/2023] [Indexed: 03/13/2023]
Abstract
PURPOSE Despite presumed relevance to ocular diseases, the viscoelastic properties of the posterior human eye have not been evaluated in detail. We performed creep testing to characterize the viscoelastic properties of ocular regions, including the sclera, optic nerve (ON) and ON sheath. METHODS We tested 10 pairs of postmortem human eyes of average age 77 ± 17 years, consisting of 5 males and 5 females. Except for the ON that was tested in native shape, tissues were trimmed into rectangles. With physiologic temperature and constant wetting, tissues were rapidly loaded to tensile stress that was maintained by servo feedback as length was monitored for 1,500 sec. Relaxation modulus was computed using Prony series, and Deborah numbers estimated for times scales of physiological eye movements. RESULTS Correlation between creep rate and applied stress level was negligible for all tissues, permitting description as linear viscoelastic materials characterized by lumped parameter compliance equations for limiting behaviors. The ON was the most compliant, and anterior sclera least compliant, with similar intermediate values for posterior sclera and ON sheath. Sensitivity analysis demonstrated that linear behavior eventually become dominant after long time. For the range of typical pursuit tracking, all tissues exhibit Debora numbers less than 75, and should be regarded as viscoelastic. With a 6.7 Deborah number, this is especially so for the ON during pursuit and convergence. CONCLUSIONS Posterior ocular tissues exhibit creep consistent with linear viscoelasticity necessary for describing biomechanical behavior of the ON, its sheath, and sclera during physiological eye movements and eccentric ocular fixations. Running Head: Tensile Creep of Human Ocular Tissues.
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Affiliation(s)
- Dooseop Song
- Department of Mechanical Engineering, University of California, Los Angeles, United States; Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, United States
| | - Seongjin Lim
- Department of Mechanical Engineering, University of California, Los Angeles, United States; Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, United States
| | - Joseph Park
- Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, United States
| | - Joseph L Demer
- Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, United States; Department of Bioengineering, University of California, Los Angeles, United States; Department of Neurology, University of California, Los Angeles, United States.
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González-Iglesias E, López-Vázquez A, Noval S, Nieves-Moreno M, Granados-Fernández M, Arruti N, Rosa-Pérez I, Pacio-Míguez M, Montaño VEF, Rodríguez-Solana P, del Pozo A, Santos-Simarro F, Vallespín E. Next-Generation Sequencing Screening of 43 Families with Non-Syndromic Early-Onset High Myopia: A Clinical and Genetic Study. Int J Mol Sci 2022; 23:4233. [PMID: 35457050 PMCID: PMC9031962 DOI: 10.3390/ijms23084233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 04/04/2022] [Indexed: 02/01/2023] Open
Abstract
Early-onset high myopia (EoHM) is a disease that causes a spherical refraction error of ≥-6 diopters before 10 years of age, with potential multiple ocular complications. In this article, we report a clinical and genetic study of 43 families with EoHM recruited in our center. A complete ophthalmological evaluation was performed, and a sample of peripheral blood was obtained from proband and family members. DNA was analyzed using a customized next-generation sequencing panel that included 419 genes related to ophthalmological disorders with a suspected genetic cause, and genes related to EoHM pathogenesis. We detected pathogenic and likely pathogenic variants in 23.9% of the families and detected variants of unknown significance in 76.1%. Of these, 5.7% were found in genes related to non-syndromic EoHM, 48.6% in genes associated with inherited retinal dystrophies that can include a syndromic phenotype, and 45.7% in genes that are not directly related to EoHM or retinal dystrophy. We found no candidate genes in 23% of the patients, which suggests that further studies are needed. We propose a systematic genetic analysis for patients with EoHM because it helps with follow-up, prognosis and genetic counseling.
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Affiliation(s)
- Eva González-Iglesias
- Section of Molecular Ophthalmology, Medical and Molecular Genetics Institute (INGEMM) IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (E.G.-I.); (V.E.F.M.); (P.R.-S.)
| | - Ana López-Vázquez
- Department of Ophthalmology, La Paz University Hospital, 28046 Madrid, Spain; (A.L.-V.); (S.N.); (M.N.-M.); (M.G.-F.); (N.A.); (I.R.-P.)
| | - Susana Noval
- Department of Ophthalmology, La Paz University Hospital, 28046 Madrid, Spain; (A.L.-V.); (S.N.); (M.N.-M.); (M.G.-F.); (N.A.); (I.R.-P.)
| | - María Nieves-Moreno
- Department of Ophthalmology, La Paz University Hospital, 28046 Madrid, Spain; (A.L.-V.); (S.N.); (M.N.-M.); (M.G.-F.); (N.A.); (I.R.-P.)
| | - María Granados-Fernández
- Department of Ophthalmology, La Paz University Hospital, 28046 Madrid, Spain; (A.L.-V.); (S.N.); (M.N.-M.); (M.G.-F.); (N.A.); (I.R.-P.)
| | - Natalia Arruti
- Department of Ophthalmology, La Paz University Hospital, 28046 Madrid, Spain; (A.L.-V.); (S.N.); (M.N.-M.); (M.G.-F.); (N.A.); (I.R.-P.)
| | - Irene Rosa-Pérez
- Department of Ophthalmology, La Paz University Hospital, 28046 Madrid, Spain; (A.L.-V.); (S.N.); (M.N.-M.); (M.G.-F.); (N.A.); (I.R.-P.)
| | - Marta Pacio-Míguez
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (M.P.-M.); (A.d.P.); (F.S.-S.)
- Section of Neurodevelopmental Disorders, Medical and Molecular Genetics Institute (INGEMM) IdiPaz, La Paz University Hospital, 28046 Madrid, Spain
| | - Victoria E. F. Montaño
- Section of Molecular Ophthalmology, Medical and Molecular Genetics Institute (INGEMM) IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (E.G.-I.); (V.E.F.M.); (P.R.-S.)
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (M.P.-M.); (A.d.P.); (F.S.-S.)
| | - Patricia Rodríguez-Solana
- Section of Molecular Ophthalmology, Medical and Molecular Genetics Institute (INGEMM) IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (E.G.-I.); (V.E.F.M.); (P.R.-S.)
| | - Angela del Pozo
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (M.P.-M.); (A.d.P.); (F.S.-S.)
- Section of Clinical Bioinformatics, Medical and Molecular Genetics Institute (INGEMM) IdiPaz, La Paz University Hospital, 28046 Madrid, Spain
| | - Fernando Santos-Simarro
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (M.P.-M.); (A.d.P.); (F.S.-S.)
- Section of Clinical Genetics, Medical and Molecular Genetics Institute (INGEMM) IdiPaz, La Paz University Hospital, 28046 Madrid, Spain
| | - Elena Vallespín
- Section of Molecular Ophthalmology, Medical and Molecular Genetics Institute (INGEMM) IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (E.G.-I.); (V.E.F.M.); (P.R.-S.)
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (M.P.-M.); (A.d.P.); (F.S.-S.)
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Miesfeld JB, Ghiasvand NM, Marsh-Armstrong B, Marsh-Armstrong N, Miller EB, Zhang P, Manna SK, Zawadzki RJ, Brown NL, Glaser T. The Atoh7 remote enhancer provides transcriptional robustness during retinal ganglion cell development. Proc Natl Acad Sci U S A 2020; 117:21690-21700. [PMID: 32817515 PMCID: PMC7474671 DOI: 10.1073/pnas.2006888117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The retinal ganglion cell (RGC) competence factor ATOH7 is dynamically expressed during retinal histogenesis. ATOH7 transcription is controlled by a promoter-adjacent primary enhancer and a remote shadow enhancer (SE). Deletion of the ATOH7 human SE causes nonsyndromic congenital retinal nonattachment (NCRNA) disease, characterized by optic nerve aplasia and total blindness. We used genome editing to model NCRNA in mice. Deletion of the murine SE reduces Atoh7 messenger RNA (mRNA) fivefold but does not recapitulate optic nerve loss; however, SEdel/knockout (KO) trans heterozygotes have thin optic nerves. By analyzing Atoh7 mRNA and protein levels, RGC development and survival, and chromatin landscape effects, we show that the SE ensures robust Atoh7 transcriptional output. Combining SE deletion and KO and wild-type alleles in a genotypic series, we determined the amount of Atoh7 needed to produce a normal complement of adult RGCs, and the secondary consequences of graded reductions in Atoh7 dosage. Together, these data reveal the workings of an evolutionary fail-safe, a duplicate enhancer mechanism that is hard-wired in the machinery of vertebrate retinal ganglion cell genesis.
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Affiliation(s)
- Joel B Miesfeld
- Department of Cell Biology and Human Anatomy, University of California Davis School of Medicine, Davis, CA 95616
| | - Noor M Ghiasvand
- Department of Biology, Grand Valley State University, Allendale, MI 49401
- Functional Neurosurgery Research Center, Shohada Tajrish Neurosurgical Center of Excellence, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Brennan Marsh-Armstrong
- Department of Ophthalmology and Vision Science, University of California Davis School of Medicine, Sacramento, CA 95817
| | - Nicholas Marsh-Armstrong
- Department of Ophthalmology and Vision Science, University of California Davis School of Medicine, Sacramento, CA 95817
| | - Eric B Miller
- Department of Cell Biology and Human Anatomy, University of California Davis School of Medicine, Davis, CA 95616
| | - Pengfei Zhang
- Department of Cell Biology and Human Anatomy, University of California Davis School of Medicine, Davis, CA 95616
| | - Suman K Manna
- Department of Cell Biology and Human Anatomy, University of California Davis School of Medicine, Davis, CA 95616
| | - Robert J Zawadzki
- Department of Ophthalmology and Vision Science, University of California Davis School of Medicine, Sacramento, CA 95817
| | - Nadean L Brown
- Department of Cell Biology and Human Anatomy, University of California Davis School of Medicine, Davis, CA 95616
| | - Tom Glaser
- Department of Cell Biology and Human Anatomy, University of California Davis School of Medicine, Davis, CA 95616;
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Shin A, Yoo L, Park J, Demer JL. Finite Element Biomechanics of Optic Nerve Sheath Traction in Adduction. J Biomech Eng 2018; 139:2648719. [PMID: 28787473 DOI: 10.1115/1.4037562] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Indexed: 02/01/2023]
Abstract
Historical emphasis on increased intraocular pressure (IOP) in the pathogenesis of glaucoma has been challenged by the recognition that many patients lack abnormally elevated IOP. We employed finite element analysis (FEA) to infer contribution to optic neuropathy from tractional deformation of the optic nerve head (ONH) and lamina cribrosa (LC) by extraocular muscle (EOM) counterforce exerted when optic nerve (ON) redundancy becomes exhausted in adduction. We characterized assumed isotropic Young's modulus of fresh adult bovine ON, ON sheath, and peripapillary and peripheral sclera by tensile elongation in arbitrary orientations of five specimens of each tissue to failure under physiological temperature and humidity. Physical dimensions of the FEA were scaled to human histological and magnetic resonance imaging (MRI) data and used to predict stress and strain during adduction 6 deg beyond ON straightening at multiple levels of IOP. Young's modulus of ON sheath of 44.6 ± 5.6 MPa (standard error of mean) greatly exceeded that of ON at 5.2 ± 0.4 MPa, peripapillary sclera at 5.5 ± 0.8 MPa, and peripheral sclera at 14.0 ± 2.3 MPa. FEA indicated that adduction induced maximum stress and strain in the temporal ONH. In the temporal LC, the maximum stress was 180 kPa, and the maximum strain was ninefold larger than produced by IOP elevation to 45 mm Hg. The simulation suggests that ON sheath traction by adduction concentrates far greater mechanical stress and strain in the ONH region than does elevated IOP, supporting the novel concept that glaucomatous optic neuropathy may result at least partly from external traction on the ON, rather than exclusively on pressure on the ON exerted from within the eye.
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Affiliation(s)
- Andrew Shin
- Department of Ophthalmology, Stein Eye Institute, Los Angeles, CA 90095
| | - Lawrence Yoo
- Department of Ophthalmology, Stein Eye Institute, Los Angeles, CA 90095; Intelon Optics Inc., Cambridge, MA 02138-4430
| | - Joseph Park
- Department of Ophthalmology, Stein Eye Institute, Los Angeles, CA 90095; Department of Mechanical Engineering, University of California, Los Angeles, CA 90095
| | - Joseph L Demer
- Arthur L. Rosenbaum Professor of Pediatric Ophthalmology Department of Ophthalmology, Stein Eye Institute, Los Angeles, CA 90095 e-mail: ; Biomedical Engineering Interdepartmental Program, University of California, Los Angeles, CA 90095;Neuroscience Interdepartmental Program, University of California, Los Angeles, CA 90095; Department of Neurology, University of California, Los Angeles, CA 90095
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Demer JL, Clark RA, Suh SY, Giaconi JA, Nouri-Mahdavi K, Law SK, Bonelli L, Coleman AL, Caprioli J. Magnetic Resonance Imaging of Optic Nerve Traction During Adduction in Primary Open-Angle Glaucoma With Normal Intraocular Pressure. Invest Ophthalmol Vis Sci 2017; 58:4114-4125. [PMID: 28829843 PMCID: PMC5566384 DOI: 10.1167/iovs.17-22093] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Purpose We used magnetic resonance imaging (MRI) to ascertain effects of optic nerve (ON) traction in adduction, a phenomenon proposed as neuropathic in primary open-angle glaucoma (POAG). Methods Seventeen patients with POAG and maximal IOP ≤ 20 mm Hg, and 31 controls underwent MRI in central gaze and 20° to 30° abduction and adduction. Optic nerve and sheath area centroids permitted computation of midorbital lengths versus minimum paths. Results Average mean deviation (±SEM) was −8.2 ± 1.2 dB in the 15 patients with POAG having interpretable perimetry. In central gaze, ON path length in POAG was significantly more redundant (104.5 ± 0.4% of geometric minimum) than in controls (102.9 ± 0.4%, P = 2.96 × 10−4). In both groups the ON became significantly straighter in adduction (28.6 ± 0.8° in POAG, 26.8 ± 1.1° in controls) than central gaze and abduction. In adduction, the ON in POAG straightened to 102.0% ± 0.2% of minimum path length versus 104.5% ± 0.4% in central gaze (P = 5.7 × 10−7), compared with controls who straightened to 101.6% ± 0.1% from 102.9% ± 0.3% in central gaze (P = 8.7 × 10−6); and globes retracted 0.73 ± 0.09 mm in POAG, but only 0.07 ± 0.08 mm in controls (P = 8.8 × 10−7). Both effects were confirmed in age-matched controls, and remained significant after correction for significant effects of age and axial globe length (P = 0.005). Conclusions Although tethering and elongation of ON and sheath are normal in adduction, adduction is associated with abnormally great globe retraction in POAG without elevated IOP. Traction in adduction may cause mechanical overloading of the ON head and peripapillary sclera, thus contributing to or resulting from the optic neuropathy of glaucoma independent of IOP.
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Affiliation(s)
- Joseph L Demer
- Department of Ophthalmology, University of California, Los Angeles, California, United States.,Stein Eye Institute, University of California, Los Angeles, California, United States.,Biomedical Engineering Interdepartmental Program, University of California, Los Angeles, California, United States.,Neuroscience Interdepartmental Program, University of California, Los Angeles, California, United States.,Department of Neurology, University of California, Los Angeles, California, United States
| | - Robert A Clark
- Department of Ophthalmology, University of California, Los Angeles, California, United States.,Stein Eye Institute, University of California, Los Angeles, California, United States
| | - Soh Youn Suh
- Department of Ophthalmology, University of California, Los Angeles, California, United States
| | - JoAnn A Giaconi
- Department of Ophthalmology, University of California, Los Angeles, California, United States.,Stein Eye Institute, University of California, Los Angeles, California, United States
| | - Kouros Nouri-Mahdavi
- Department of Ophthalmology, University of California, Los Angeles, California, United States.,Stein Eye Institute, University of California, Los Angeles, California, United States
| | - Simon K Law
- Department of Ophthalmology, University of California, Los Angeles, California, United States.,Stein Eye Institute, University of California, Los Angeles, California, United States
| | - Laura Bonelli
- Department of Ophthalmology, University of California, Los Angeles, California, United States.,Stein Eye Institute, University of California, Los Angeles, California, United States
| | - Anne L Coleman
- Department of Ophthalmology, University of California, Los Angeles, California, United States.,Stein Eye Institute, University of California, Los Angeles, California, United States
| | - Joseph Caprioli
- Department of Ophthalmology, University of California, Los Angeles, California, United States.,Stein Eye Institute, University of California, Los Angeles, California, United States
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Chang MY, Shin A, Park J, Nagiel A, Lalane RA, Schwartz SD, Demer JL. Deformation of Optic Nerve Head and Peripapillary Tissues by Horizontal Duction. Am J Ophthalmol 2017; 174:85-94. [PMID: 27751810 DOI: 10.1016/j.ajo.2016.10.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 10/03/2016] [Accepted: 10/06/2016] [Indexed: 12/11/2022]
Abstract
PURPOSE To ascertain deformation of the optic nerve head (ONH) and peripapillary tissues caused by horizontal duction. DESIGN Prospective, experimental study. METHODS Optical coherence tomography of the ONH region was performed in 23 eyes of 12 normal volunteers in central gaze and increasing (10, 20, and 30 degrees) adduction and abduction. Main outcome measures were changes from central gaze in the configuration of the ONH and peripapillary tissues in eccentric gazes. RESULTS Adduction but not abduction was associated with significant, progressive relative posterior displacement of the temporal peripapillary retinal pigment epithelium (tRPE) from its position in central gaze reaching 49 ± 10 μm in 30-degree adduction (standard error of mean, P < .0001). Absolute (anterior or posterior) optic cup displacement (OCD) averaged 41 ± 7 μm in 30-degree adduction. Linear regression showed significant effect of adduction on absolute OCD (slope 1.09 ± 0.36 μm/degree, P = .0037). In 20-degree and 30-degree adduction, all eyes exhibited significant progressive temporal ONH tilting reaching 3.1 ± 0.4 degrees in 30-degree adduction (P < .0001). Abduction was not associated with significant peripapillary RPE displacement, OCD, or ONH tilt. Both nasal and temporal peripapillary choroid averaged 9-19 μm thinner in adduction and abduction than in central gaze (P < .02). CONCLUSIONS Adduction temporally tilts and displaces the prelaminar ONH and peripapillary tissues. Both adduction and abduction compress the peripapillary choroid. These effects support magnetic resonance imaging and biomechanical evidence that adduction imposes strain on the ONH and peripapillary tissues. Repetitive strain from eye movements over decades might in susceptible individuals lead to optic neuropathies such as normal tension glaucoma.
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Elsheikh A, Phillips JR. Is scleral cross-linking a feasible treatment for myopia control? Ophthalmic Physiol Opt 2013; 33:385-9. [PMID: 23662971 DOI: 10.1111/opo.12043] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, UK.
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Theocharis IP, Lima LH. Vitreoretinal interface in central serous choroidopathy: a retrospective case-control study. Acta Ophthalmol 2012; 90:e505-11. [PMID: 22863356 DOI: 10.1111/j.1755-3768.2012.02488.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE To investigate the frequency and patterns of vitreoretinal adherence in central serous choroidopathy (CSC) using spectral domain optical coherence tomography (SD-OCT) imaging and compare them with normal subject. METHODS A descriptive observational analytical retrospective case-control study. The study patients were split into non-chronic and chronic CSC groups and compared with an age- and gender-matched control group composed of healthy individuals without CSC. Five patterns of vitreoretinal adherence were defined: lacunae, partial posterior vitreous detachment (partial-PVD), epiretinal membrane (ERM), focal vitreomacular adherence (VMA) and no recognizable pattern. Statistical analysis was performed. RESULTS One hundred and four eyes of 52 patients were included in this study. Forty-eight eyes of 24 patients had chronic CSC and 56 eyes of 28 patients had non-chronic CSC. The control group for chronic CSC included 96 normal eyes of 48 subjects, and the control group for non-chronic CSC included one hundred and twelve normal eyes of 56 subjects. We found a recognizable pattern of the vitreoretinal interface (lacuna, partial-PPV, VMA or ERM) more often in non-chronic CSC (p = 0.0001, OR = 6.51 and CI = 2.71-15.62) and in chronic CSC patients (p = 0.001, OR = 4.05, CI: 1.77-9.57) than in normal subjects. CONCLUSION The proportion of patterns of vitreoretinal adherence and interface found in CSC changes with age and manifests differently compared with normal eyes. The results indicate early changes in CSC patients younger than 40 years of old bilaterally.
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Sibony P, Kupersmith MJ, Rohlf FJ. Shape analysis of the peripapillary RPE layer in papilledema and ischemic optic neuropathy. Invest Ophthalmol Vis Sci 2011; 52:7987-95. [PMID: 21896851 DOI: 10.1167/iovs.11-7918] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Geometric morphometrics (GM) was used to analyze the shape of the peripapillary retinal pigment epithelium-Bruch's membrane (RPE/BM) layer imaged on the SD-OCT 5-line raster in normal subjects and in patients with papilledema and ischemic optic neuropathy. METHODS Three groups of subjects were compared: 30 normals, 20 with anterior ischemic optic neuropathy (AION), and 25 with papilledema and intracranial hypertension. Twenty equidistant semilandmarks were digitized on OCT images of the RPE/BM layer spanning 2500 μm on each side of the neural canal opening (NCO). The data were analyzed using standard GM techniques, including a generalized least-squares Procrustes superimposition, principal component analysis, thin-plate spline (to visualize deformations), and permutation statistical analysis to evaluate differences in shape variables. RESULTS The RPE/BM layer in normals and AION have a characteristic V shape pointing away from the vitreous; the RPE/BM layer in papilledema has an inverted U shape, skewed nasally inward toward the vitreous. The differences were statistically significant. There was no significant difference in shapes between normals and AION. Pre- and posttreatment OCTs, in select cases of papilledema, showed that the inverted U-shaped RPE/BM moved posteriorly into a normal V shape as the papilledema resolved with weight loss or shunting. CONCLUSIONS The shape difference in papilledema, absent in AION, cannot be explained by disc edema alone. The difference is a consequence of both the translaminar pressure gradient and the material properties of the peripapillary sclera. GM offers a novel way of statistically assessing shape differences of the peripapillary optic nerve head.
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Affiliation(s)
- Patrick Sibony
- Department of Ophthalmology, Health Sciences Center, University Hospital and Medical Center, State University of New York, Stony Brook, NY 11794, USA.
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Abstract
BACKGROUND Peripapillary subretinal hemorrhage (PSH) is often found together with optic disc drusen, optic disc edema, peripapillary subretinal neovascular membranes, vitreous traction, and bleeding diatheses. Previous reports have stated that such optic disc hemorrhages are associated with intrapapillary bleeding largely in patients of Asian origin who are visually symptomatic from this process. We have encountered patients with PSH who have clinical features that differ from those described in these reports. METHODS This is a retrospective observational case series. Medical records of 10 patients with isolated peripapillary subretinal hemorrhages were reviewed for clinical characteristics and ancillary testing, including demographics, history, complete eye examination, visual fields, fundus photos, ultrasound, and fluorescein angiography (four patients) at presentation and follow-up. We excluded patients with drusen, neovascular membranes, disc edema, and intrapapillary hemorrhages. RESULTS There were 10 patients, all white women without visual symptoms, who had isolated, monocular, nasal, or superonasal peripapillary subretinal hemorrhage, a dysplastic crowded-tilted optic disc, myopia, and normal visual function. The hemorrhages resolved without sequelae over 3-6 months. The findings were frequently discovered on routine examination and suspected of representing papilledema. CONCLUSIONS We have described a benign syndrome of isolated PSH in crowded and tilted optic discs in myopic eyes of white women. The PSHs do not cause visual symptoms and resolve spontaneously. We propose that an interplay of ocular motor forces, scleral thinning, and vitreopapillary traction acting on a morphologically vulnerable optic disc explains these hemorrhages.
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Thompson JT. The Effects and Action of Scleral Buckles in the Treatment of Retinal Detachment. Retina 2006. [DOI: 10.1016/b978-0-323-02598-0.50123-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Abstract
The current state of research into experimentally induced refractive errors is reviewed. The area is analysed in three components-the transduction of defocus or deprivation, the vector for transmitting the error message from the retina to the outer tunics of the eye, and the identity of the effector for causing growth modulation in the sclera. Anatomical, pharmacological, electrophysiological and optical factors are considered in terms of which elements of the retina are necessary to support a refractive response to deprivation or defocus. Two of the current models are discussed-one emphasizing the role of the choroid in effecting ocular and refractive change, while the second model approaches the problem from the aspect of scleral changes that are associated with growth adaptation without emphasis on the error detection mechanism. A third model is proposed in which the error signal for deprivation or defocus is detected in the outer retina and where error is translated through separate signals for stimulus brightening and darkening into a net signal for fluid flow across and under the active control of the retinal pigment epithelium with the fluid communication between the vitreous chamber and the choroidal lymphatics. The directions of research both fundamental and clinical which are needed to create pharmaceutical or environmental solutions to refractive control are discussed.
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Affiliation(s)
- D P Crewther
- School of Psychological Science, La Trobe University, Bundoora, Victoria, Australia.
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David T, Smye S, Dabbs T, James T. A model for the fluid motion of vitreous humour of the human eye during saccadic movement. Phys Med Biol 1998; 43:1385-99. [PMID: 9651012 DOI: 10.1088/0031-9155/43/6/001] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
During saccadic motion the eyewall moves in a manner similar to a sinusoid or at least can be represented by a sine Fourier series. Motion of the vitreous is induced by the saccade and the vitreo-retinal interface is subjected to a time-dependent shear. This force may be a significant factor for retinal tearing in the neighbourhood of small retinal holes or tears. An analytical viscoelastic model and a numerical, Newtonian model of the motion of the vitreous are presented and compared. Under sinusoidal boundary motion the analytical model shows that a viscous wave propagates inward toward the axis of rotation and the characteristic length of this wave is a function of the Womersley number. The numerical solution indicates that the vitreous moves similarly to the analytical result with small secondary motion; however, this motion allows complete recirculation of the vitreous over large timescales. Excellent agreement is found between the analytical and numerical models. The time-dependent fluid shear is evaluated and from the analytical solution the maximum value of this is found to be proportional to R0 square root of v(omega)3, where R0 is the eye radius, v the modified complex viscosity and omega the sinusoidal frequency. This indicates that myopes have a larger shear force exerted on them by virtue of the larger eye size. Further work is directed toward a model which links the stress found in the sclera to that exerted on the vitreo-retinal interface by the vitreous fluid motion.
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Affiliation(s)
- T David
- School of Mechanical Engineering, University of Leeds, UK
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