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Park SA, Komáromy AM. Biomechanics of the optic nerve head and sclera in canine glaucoma: A brief review. Vet Ophthalmol 2021; 24:316-325. [PMID: 34402566 DOI: 10.1111/vop.12923] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 06/04/2021] [Accepted: 07/25/2021] [Indexed: 01/17/2023]
Abstract
Glaucoma is a leading cause of irreversible blindness, a progressive optic neuropathy with retinal ganglion cell (RGC) death beginning in the optic nerve head (ONH). A primary risk factor for developing glaucoma is elevated intraocular pressure (IOP). Reducing IOP is the only treatment proven to be effective at delaying disease progression. Nevertheless, even when patients have their IOP reduced, the majority of them continue to lose vision. There are, in both humans and dogs, significant interindividual variabilities in susceptibilities to IOP-induced optic nerve damage. Vision loss progresses much more slowly in Beagles with open-angle glaucoma (OAG) caused by ADAMTS10 mutation. This can be attributed to the mutation-related altered ocular biomechanical properties. The principal site of optic nerve (ON) damage in glaucoma is the ONH. It is suggested that the biomechanical properties of the ONH and the surrounding peripapillary sclera (PPS) contribute to glaucoma development and progression. As far as the beneficial biomechanical properties of the ONH and PPS for a decreased susceptibility and slow progression of glaucoma, data are inconsistent and conflicting. Recent biomechanical studies on beagles with ADAMTS10 mutation demonstrated that the mutant dogs have mechanically weak posterior sclera. This weakness was associated with a reduced collagen density and a lower proportion of insoluble collagen. These changes, observed before glaucoma development, were considered intrinsic characteristics caused by the mutation rather than a secondary effect of IOP elevation. Further studies of ADAMTS10-OAG may elucidate the effects of altered biomechanical properties of ONH and PPS in determining the glaucoma progression.
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Affiliation(s)
- Shin Ae Park
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, USA
| | - András M Komáromy
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA
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Mysona BA, Segar S, Hernandez C, Kim C, Zhao J, Mysona D, Bollinger KE. QuPath Automated Analysis of Optic Nerve Degeneration in Brown Norway Rats. Transl Vis Sci Technol 2020; 9:22. [PMID: 32714648 PMCID: PMC7353320 DOI: 10.1167/tvst.9.3.22] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Purpose A novel application of QuPath open-source digital analysis software is used to provide in-depth morphological analysis of progressive optic nerve (ON) degeneration in rats. Methods QuPath software was adapted to assess axon and gliotic morphology in toluidine blue-stained, Brown Norway rat ON light micrographs. QuPath axon numbers, density, size distributions, and gliotic areas were obtained from test images and ON cross-sections separated by damage grade. QuPath results were compared with manual counting, AxonJ, and electron microscopy axon estimates. Results QuPath-derived axon number, density, and diameter decreased with increasing ON damage. Axon density negatively correlated with gliotic areas in test images (R2 = 0.759; P < 0.0001; N = 40) and in ON cross-sections (R2 = 0.803; P < 0.0004; N = 10). Although axon losses occurred across most axon diameters, large axons were more susceptible to degeneration. The exception was swollen axons > 2 µm, which increased in moderately but not severely damaged images. QuPath axon counts correlated strongly with manual counts of test images (R2 = 0.956; P < 0.0001). QuPath outperformed AxonJ on test images and total ON axon counts. Compared to electron microscopy analysis, QuPath undercounted ON axons; however, correlation between the methods was robust (R2 = 0.797; P < 0.001; N = 10). Conclusions QuPath analysis reliably identified axon loss, axon morphology changes, and gliotic expansion that occurred in degenerating ONs. Translational Relevance QuPath is a valuable tool for rapid, automated, analysis of healthy and degenerating ONs. Reproducible preclinical studies for new glaucoma treatments depend on unbiased in-depth analysis of ON pathology. This was provided by the QuPath approach.
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Affiliation(s)
- Barbara A Mysona
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, USA.,James and Jean Culver Vision Discovery Institute, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Sharmila Segar
- Medical College of Georgia at Augusta University, Augusta, GA, USA
| | | | - Christian Kim
- Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Jing Zhao
- James and Jean Culver Vision Discovery Institute, Medical College of Georgia at Augusta University, Augusta, GA, USA.,Department of Ophthalmology, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - David Mysona
- Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Kathryn E Bollinger
- James and Jean Culver Vision Discovery Institute, Medical College of Georgia at Augusta University, Augusta, GA, USA.,Department of Ophthalmology, Medical College of Georgia at Augusta University, Augusta, GA, USA
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Identifying central and peripheral nerve fibres with an artificial intelligence approach. Appl Soft Comput 2018. [DOI: 10.1016/j.asoc.2018.03.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Teixeira LBC, Hoeve JNV, Mayer JA, Dubielzig RR, Smith CM, Radcliff AB, Duncan ID. Modeling the Chronic Loss of Optic Nerve Axons and the Effects on the Retinal Nerve Fiber Layer Structure in Primary Disorder of Myelin. Invest Ophthalmol Vis Sci 2016; 57:4859-4868. [PMID: 27654412 PMCID: PMC5032912 DOI: 10.1167/iovs.16-19871] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Purpose We determined whether the chronic lack of optic nerve myelination and subsequent axon loss is associated with optical coherence tomography (OCT) changes in the retinal nerve fiber layer (RNFL), and whether this models what occurs in multiple sclerosis (MS) and confers its use as a surrogate marker for axon degeneration. Methods Using an animal model of Pelizaeus-Merzbacher disease (shp) bilateral longitudinal measurements of the peripapillary RNFL (spectral-domain OCT), electroretinograms (ERG), and visual evoked potentials (VEP) were performed in affected and control animals from 5 months to 2 years and in individual animals at single time points. Light and electron microscopy of the optic nerve and retina and histomorphometric measurements of the RNFL were compared to OCT data. Results Of the shp animals, 17% had an average reduction of OCT RNFL thickness on the superior retinal quadrant compared to controls (P < 0.05). Electroretinograms showed normal photopic A- and B-waves but flash VEPs were disorganized in shp animals. Morphologically, the shp retinas and optic nerves revealed significant RNFL thinning (P < 0.001) without retinal ganglion cell (RGC) loss, decrease total and relative retinal axonal area, and loss of optic nerve axons. There was strong positive correlation between OCT and morphometric RNFL thickness measurements (r = 0.878, P = 0.004). Conclusion The loss of optic nerve axons demonstrated in the shp model resulted in moderate thinning of the RNFL confirmed by OCT and histology. These results indicate that OCT-derived RNFL measurement can be a useful surrogate biomarker of optic nerve axon loss and potentially disease progression in demyelinating diseases.
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Affiliation(s)
- Leandro B C Teixeira
- Department of Pathobiological Sciences School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States
| | - James N Ver Hoeve
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, United States
| | - Joshua A Mayer
- Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States
| | - Richard R Dubielzig
- Department of Pathobiological Sciences School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States
| | - Chelsey M Smith
- Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States
| | - Abigail B Radcliff
- Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States
| | - Ian D Duncan
- Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States
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Palko JR, Morris HJ, Pan X, Harman CD, Koehl KL, Gelatt KN, Plummer CE, Komáromy AM, Liu J. Influence of Age on Ocular Biomechanical Properties in a Canine Glaucoma Model with ADAMTS10 Mutation. PLoS One 2016; 11:e0156466. [PMID: 27271467 PMCID: PMC4894564 DOI: 10.1371/journal.pone.0156466] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 05/13/2016] [Indexed: 11/29/2022] Open
Abstract
Soft tissue often displays marked age-associated stiffening. This study aims to investigate how age affects scleral biomechanical properties in a canine glaucoma model with ADAMTS10 mutation, whose extracellular matrix is concomitantly influenced by the mutation and an increased mechanical load from an early age. Biomechanical data was acquired from ADAMTS10-mutant dogs (n = 10, 21 to 131 months) and normal dogs (n = 5, 69 to 113 months). Infusion testing was first performed in the whole globes to measure ocular rigidity. After infusion experiments, the corneas were immediately trephined to prepare scleral shells that were mounted on a pressurization chamber to measure strains in the posterior sclera using an inflation testing protocol. Dynamic viscoelastic mechanical testing was then performed on dissected posterior scleral strips and the data were combined with those reported earlier by our group from the same animal model (Palko et al, IOVS 2013). The association between age and scleral biomechanical properties was evaluated using multivariate linear regression. The relationships between scleral properties and the mean and last measured intraocular pressure (IOP) were also evaluated. Our results showed that age was positively associated with complex modulus (p<0.001) and negatively associated with loss tangent (p<0.001) in both the affected and the normal groups, suggesting an increased stiffness and decreased mechanical damping with age. The regression slopes were not different between the groups, although the complex modulus was significantly lower in the affected group (p = 0.041). The posterior circumferential tangential strain was negatively correlated with complex modulus (R = -0.744, p = 0.006) showing consistent mechanical evaluation between the testing methods. Normalized ocular rigidity was negatively correlated with the last IOP in the affected group (p = 0.003). Despite a mutation that affects the extracellular matrix and a chronic IOP elevation in the affected dogs, age-associated scleral stiffening and loss of mechanical damping were still prominent and had a similar rate of change as in the normal dogs.
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Affiliation(s)
- Joel R. Palko
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States of America
- Department of Ophthalmology, Washington University, St. Louis, Missouri, United States of America
| | - Hugh J. Morris
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States of America
| | - Xueliang Pan
- Center for Biostatistics, Ohio State University, Columbus, OH, United States of America
| | - Christine D. Harman
- Department of Small Animal Clinical Sciences, Michigan State University, Lansing, Michigan, United States of America
| | - Kristin L. Koehl
- Department of Small Animal Clinical Sciences, Michigan State University, Lansing, Michigan, United States of America
| | - Kirk N. Gelatt
- Department of Small Animal Clinical Sciences, University of Florida, Gainesville, Florida, United States of America
| | - Caryn E. Plummer
- Department of Small Animal Clinical Sciences, University of Florida, Gainesville, Florida, United States of America
| | - András M. Komáromy
- Department of Small Animal Clinical Sciences, Michigan State University, Lansing, Michigan, United States of America
- Department of Small Animal Clinical Sciences, University of Florida, Gainesville, Florida, United States of America
- Department of Clinical Studies, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail: (JL); (AMK)
| | - Jun Liu
- Department of Biomedical Engineering, Ohio State University, Columbus, Ohio, United States of America
- Department of Ophthalmology, Ohio State University, Columbus, Ohio, United States of America
- * E-mail: (JL); (AMK)
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Townsend WM, Langohr IM, Mouney MC, Moore GE. Feasibility of aqueous shunts for reduction of intraocular pressure in horses. Equine Vet J 2013; 46:239-43. [PMID: 23662686 DOI: 10.1111/evj.12098] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 04/26/2013] [Indexed: 11/30/2022]
Abstract
REASONS FOR PERFORMING STUDY Based on the current literature, neither medical, surgical nor combination therapy adequately controls equine glaucoma for many horses. Aqueous shunts have been useful in other species to control glaucoma. OBJECTIVES To determine whether aqueous shunts in normal equine eyes significantly reduce intraocular pressure (IOP) without causing vision threatening complications. STUDY DESIGN Prospective experimental trial. METHODS Aqueous shunts were placed in 7 normal eyes of 4 horses. The shunts were placed dorsotemporally. Examinations were initially performed daily for 7 days and after that every 3 days through 4 weeks after implantation. Horses were then subjected to euthanasia and globes enucleated for routine histological examination. The IOPs for each day post operatively were compared to the preoperative value (Day -1) using a Wilcoxon signed ranks test. Significance was set at P<0.05. RESULTS The mean IOP preoperatively (20.7 ± 3.0 mmHg) was significantly higher than on any post operative day (P values ranged from 0.018 to 0.048). The aqueous shunts remained in situ for the entire study. Two eyes developed corneal ulcers that resolved. Shallow anterior chambers were noted in 2 eyes after shunt placement, which normalised after placement of full eye cup masks. Histologically, 7/7 eyes had fibrosis surrounding the implant. Minimal peripheral neovascularisation and neutrophilic keratitis were noted in 5/7 eyes. Corneal damage was scored as none in 3/7, mild in 2/7, moderate in 1/7 and marked in 1/7 eyes. CONCLUSIONS After placement of aqueous shunts, a significant decrease in IOP was noted from preoperatively (Day -1) to Day 28 despite fibrosis surrounding the implants. No vision threatening complications were noted. POTENTIAL RELEVANCE Aqueous shunts may represent a feasible therapeutic option for equine glaucoma. The results of this study suggest that further studies in glaucomatous horses would be warranted.
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Affiliation(s)
- W M Townsend
- Department of Veterinary Clinical Sciences, Purdue University, Indiana, USA
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Reynaud J, Cull G, Wang L, Fortune B, Gardiner S, Burgoyne CF, Cioffi GA. Automated quantification of optic nerve axons in primate glaucomatous and normal eyes--method and comparison to semi-automated manual quantification. Invest Ophthalmol Vis Sci 2012; 53:2951-9. [PMID: 22467571 DOI: 10.1167/iovs.11-9274] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To describe an algorithm and software application (APP) for 100% optic nerve axon counting and to compare its performance with a semi-automated manual (SAM) method in optic nerve cross-section images (images) from normal and experimental glaucoma (EG) nonhuman primate (NHP) eyes. METHODS ON cross sections from eight EG eyes from eight NHPs, five EG and five normal eyes from five NHPs, and 12 normal eyes from 12 NHPs were imaged at 100×. Calibration (n = 500) and validation (n = 50) image sets ranging from normal to end-stage damage were assembled. Correlation between APP and SAM axon counts was assessed by Deming regression within the calibration set and a compensation formula was generated to account for the subtle, systematic differences. Then, compensated APP counts for each validation image were compared with the mean and 95% confidence interval of five SAM counts of the validation set performed by a single observer. RESULTS Calibration set APP counts linearly correlated to SAM counts (APP = 10.77 + 1.03 [SAM]; R(2) = 0.94, P < 0.0001) in normal to end-stage damage images. In the validation set, compensated APP counts fell within the 95% confidence interval of the SAM counts in 42 of the 50 images and were within 12 axons of the confidence intervals in six of the eight remaining images. Uncompensated axon density maps for the normal and EG eyes of a representative NHP were generated. CONCLUSIONS An APP for 100% ON axon counts has been calibrated and validated relative to SAM counts in normal and EG NHP eyes.
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Affiliation(s)
- Juan Reynaud
- Devers Eye Institute, Legacy Health System, Portland, Oregon 97232, USA
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Casson RJ, Chidlow G, Wood JPM, Crowston JG, Goldberg I. Definition of glaucoma: clinical and experimental concepts. Clin Exp Ophthalmol 2012; 40:341-9. [PMID: 22356435 DOI: 10.1111/j.1442-9071.2012.02773.x] [Citation(s) in RCA: 288] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Glaucoma is a term describing a group of ocular disorders with multi-factorial etiology united by a clinically characteristic intraocular pressure-associated optic neuropathy. It is not a single entity and is sometimes referred to in the plural as the glaucomas. All forms are potentially progressive and can lead to blindness. The diverse conditions that comprise glaucoma are united by a clinically characteristic optic neuropathy: glaucomatous optic neuropathy (GON). Evidence suggests that the primary site of neurological injury is at the optic nerve head. This fact enables the conditions to be grouped, irrespective of the causal mechanism(s). The term experimental glaucoma implies model resemblance to the human condition. We propose that 'experimental glaucoma' be restricted to animal models with demonstrable features of GON and/or evidence of a primary axonopathy at the optic nerve head. A fundamental inadequacy in this framework is any reference to the pathogenesis of GON, which remains unclear.
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Affiliation(s)
- Robert J Casson
- South Australian Institute of Ophthalmology, Hanson Institute and Adelaide University, Adelaide, South Australia, Australia.
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Kuchtey J, Olson LM, Rinkoski T, Mackay EO, Iverson TM, Gelatt KN, Haines JL, Kuchtey RW. Mapping of the disease locus and identification of ADAMTS10 as a candidate gene in a canine model of primary open angle glaucoma. PLoS Genet 2011; 7:e1001306. [PMID: 21379321 PMCID: PMC3040645 DOI: 10.1371/journal.pgen.1001306] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Accepted: 01/12/2011] [Indexed: 01/06/2023] Open
Abstract
Primary open angle glaucoma (POAG) is a leading cause of blindness worldwide, with elevated intraocular pressure as an important risk factor. Increased resistance to outflow of aqueous humor through the trabecular meshwork causes elevated intraocular pressure, but the specific mechanisms are unknown. In this study, we used genome-wide SNP arrays to map the disease gene in a colony of Beagle dogs with inherited POAG to within a single 4 Mb locus on canine chromosome 20. The Beagle POAG locus is syntenic to a previously mapped human quantitative trait locus for intraocular pressure on human chromosome 19. Sequence capture and next-generation sequencing of the entire canine POAG locus revealed a total of 2,692 SNPs segregating with disease. Of the disease-segregating SNPs, 54 were within exons, 8 of which result in amino acid substitutions. The strongest candidate variant causes a glycine to arginine substitution in a highly conserved region of the metalloproteinase ADAMTS10. Western blotting revealed ADAMTS10 protein is preferentially expressed in the trabecular meshwork, supporting an effect of the variant specific to aqueous humor outflow. The Gly661Arg variant in ADAMTS10 found in the POAG Beagles suggests that altered processing of extracellular matrix and/or defects in microfibril structure or function may be involved in raising intraocular pressure, offering specific biochemical targets for future research and treatment strategies. Primary open angle glaucoma (POAG) is a leading cause of vision loss and blindness affecting tens of millions of people. Ocular hypertension is a strong risk factor for the disease and the only effective target of treatment. Ocular hypertension results from increased resistance to outflow of aqueous humor through the trabecular meshwork, a specialized filtration tissue consisting of alternating layers of cells and connective tissue, but the specific reasons for the increased resistance are not known. The animal model for human POAG used in this study was a colony of Beagle dogs that carry an inherited form of the disease in which ocular hypertension is the primary manifestation. We have found a variant in ADAMTS10 that belongs to a family of genes that contribute to formation of extracellular matrix and may itself be involved in formation of elastic microfiber structures. We found that the ADAMTS10 protein is expressed at particularly high levels in the trabecular meshwork. The candidate variant in ADAMTS10 found in the POAG–affected Beagles suggests that altered processing of connective tissue and/or elastic microfiber defects may be involved in raising eye pressure, offering specific biochemical targets for future research and treatment strategies.
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Affiliation(s)
- John Kuchtey
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America.
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Balaratnasingam C, Morgan WH, Johnstone V, Pandav SS, Cringle SJ, Yu DY. Histomorphometric measurements in human and dog optic nerve and an estimation of optic nerve pressure gradients in human. Exp Eye Res 2009; 89:618-28. [DOI: 10.1016/j.exer.2009.06.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2008] [Revised: 05/25/2009] [Accepted: 06/02/2009] [Indexed: 11/26/2022]
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Zhao X, Pan Z, Wu J, Zhou G, Zeng Y. Automatic identification and morphometry of optic nerve fibers in electron microscopy images. Comput Med Imaging Graph 2009; 34:179-84. [PMID: 19796916 DOI: 10.1016/j.compmedimag.2009.08.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Revised: 07/18/2009] [Accepted: 08/31/2009] [Indexed: 11/19/2022]
Abstract
The neuroanatomical morphology of the optic nerve is an important description for understanding different aspects like topological distribution of nerves. Manual identification and morphometry has been usually considered as tedious, time consuming, and susceptible to error. A method that automates the identification and analysis of axons from electron micrographic images is presented. First, using region growing approach binarizes the image by combining the feature information together with spatial information, and obtains a coarse classification between myelin and non-myelin pixels. Next, identifies the axon candidates by region labeling and remove false axons on the basis of the identification ruler. Then the connected myelin sheaths are separated from each other using the maximum gradient magnitude of the outer annulus. Finally, analyses the morphological data of fibers. The developed method has been tested on a number of optic nerve images and results were presented. Regional distributions of axon caliber were unimodal. The thickness of the myelin sheath was highly correlated with the fiber diameter; hence, myelin sheath width was also distributed in a unimodal manner.
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Affiliation(s)
- Ximei Zhao
- College of Information Engineering, Qingdao University, Qingdao, China
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Grozdanic SD, Kecova H, Harper MM, Nilaweera W, Kuehn MH, Kardon RH. Functional and structural changes in a canine model of hereditary primary angle-closure glaucoma. Invest Ophthalmol Vis Sci 2009; 51:255-63. [PMID: 19661222 DOI: 10.1167/iovs.09-4081] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
PURPOSE To characterize functional and structural changes in a canine model of hereditary primary angle-closure glaucoma. METHODS Intraocular pressure (IOP) was evaluated with tonometry in a colony of glaucomatous dogs at 8, 15, 18, 20, and 30 months of age. Retinal function was evaluated using electroretinography (scotopic, photopic, and pattern). Examination of anterior segment structures was performed using gonioscopy and high-frequency ultrasonography (HFU). RESULTS A gradual rise in IOP was observed with an increase in age: 8 months, 14 mm Hg (median value); 15 months, 15.5 mm Hg; 18 months, 17.5 mm Hg; 20 months, 24 mm Hg; 30 months, 36 mm Hg. Provocative testing with mydriatic agents (tropicamide and atropine 1%) caused significant increases in IOP (35% and 50%, respectively). HFU analysis showed complete collapse of iridocorneal angles by 20 months of age. Scotopic and photopic ERG analysis did not reveal significant deficits, but pattern ERG analysis showed significantly reduced amplitudes in glaucomatous dogs (glaucoma, 3.5 +/- 0.4 muV; control, 6.2 +/- 0.3 muV; P = 0.004; Student's t-test). Histologic analysis revealed collapse of the iridocorneal angle, posterior bowing of the lamina cribrosa, swelling and loss of large retinal ganglion cells, increased glial reactivity, and increased thickening of the lamina cribrosa. CONCLUSIONS Canine hereditary angle-closure glaucoma is characterized by a progressive increase in intraocular pressure, loss of optic nerve function, and retinal ganglion cell loss.
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Affiliation(s)
- Sinisa D Grozdanic
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa 50011, USA.
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Sapienza JS. Surgical procedures for glaucoma: what the general practitioner needs to know. Top Companion Anim Med 2008; 23:38-45. [PMID: 18544331 DOI: 10.1053/j.ctsap.2007.12.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Glaucoma can be treated by medical and surgical options. Most ophthalmologists believe that patients with glaucoma are best treated with surgery. Early recognition of clinical signs and selection of the most effective type of surgery depending on the stage of glaucoma and the underlying cause are important factors in glaucoma surgery. Several surgical procedures exist for dogs with primary glaucoma, which may include a cyclodestructive technique or an aqueous outflow bypass procedure or a combination of both procedures. Salvage procedures such as enucleation, evisceration with an intrascleral prosthesis, or chemical intravitreal injection may be advised for chronically blind eyes with no hope of vision. Client compliance and expectations, therapeutic goals, status of vision (visual versus blind), financial constraints, surgical expertise, and underlying systemic disorders should be considered in the selection of the most appropriate surgical option for each patient.
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Affiliation(s)
- John S Sapienza
- Long Island Veterinary Specialists, Plainview, NY 11803, USA.
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Albrecht May C. Comparative anatomy of the optic nerve head and inner retina in non-primate animal models used for glaucoma research. Open Ophthalmol J 2008; 2:94-101. [PMID: 19516911 PMCID: PMC2694605 DOI: 10.2174/1874364100802010094] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 04/17/2008] [Accepted: 04/28/2008] [Indexed: 01/08/2023] Open
Abstract
To judge the information of experimental settings in relation to the human situation, it is crucial to be aware of morphological differences and peculiarities in the species studied. Related to glaucoma, the most important structures of the posterior eye segment are the optic nerve head including the lamina cribrosa, and the inner retinal layers. The review highlights the differences of the lamina cribrosa and its vascular supply, the prelaminar optic nerve head, and the retinal ganglion cell layer in the most widely used animal models for glaucoma research, including mouse, rat, rabbit, pig, dog, cat, chicken, and quail. Although all species show some differences to the human situation, the rabbit seems to be the most problematic animal for glaucoma research.
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Affiliation(s)
- Christian Albrecht May
- Department of Anatomy, Medical Faculty Carl Gustav Carus, Technical University Dresden, D-01307 Dresden, Germany.
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Kuchtey J, Källberg ME, Gelatt KN, Rinkoski T, Komàromy AM, Kuchtey RW. Angiopoietin-like 7 secretion is induced by glaucoma stimuli and its concentration is elevated in glaucomatous aqueous humor. Invest Ophthalmol Vis Sci 2008; 49:3438-48. [PMID: 18421092 DOI: 10.1167/iovs.07-1347] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To investigate the possibility that Angiopoietin-like 7 (ANGPTL7) protein is involved in the pathogenesis of glaucoma. METHODS Primary human trabecular meshwork (TM) cells and corneoscleral explants were stimulated with either dexamethasone (DEX) or transforming growth factor beta (TGFbeta), and ANGPTL7 protein secreted into culture medium was determined by Western blot analysis. The effect of stable overexpression of ANGPTL7 in transfected immortalized TM cell lines on collagen expression was investigated by immunocytochemistry. Localization of ANGPTL7 protein in human eyes was determined by immunohistochemistry. The concentration of ANGPTL7 protein in aqueous humor (AH) from patients with glaucoma and control patients was compared by Western blot analysis. The beagle model of primary open-angle glaucoma (POAG) was used to correlate ANGPTL7 protein levels in canine AH with disease progression. RESULTS TGFbeta and DEX stimulated secretion of ANGPTL7 protein by TM cells and corneoscleral explants. Overexpression of ANGPTL7 by immortalized TM cell lines increased expression of type I collagen. Expression of ANGPTL7 protein was located in the corneal stroma, near the limbus, and throughout the sclera, with lower expression in the TM. In the lamina cribrosa, ANGPTL7 expression was associated with the cribriform plates. The concentration of ANGPTL7 protein was elevated in AH from patients with glaucoma and increased as disease progressed in POAG beagle dogs. CONCLUSIONS Induction of ANGPTL7 secretion by glaucoma stimuli and increased concentration of ANGPTL7 in glaucomatous AH suggest that ANGPTL7 is overexpressed in glaucoma. Since overexpression of ANGPTL7 increases collagen expression, a potential disease mechanism, ANGPTL7 could have a pathogenic role in glaucoma, and may serve as a potential therapeutic target.
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Affiliation(s)
- John Kuchtey
- Department of Ophthalmology and Visual Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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García-Sánchez GA, Gil-Carrasco F, Román JJ, Brooks DE, Alvarez-Clau A, Hosgood G, Iwabe S, Moreno-Mendoza NA. Measurement of retinal nerve fiber layer thickness in normal and glaucomatous Cocker Spaniels by scanning laser polarimetry. Vet Ophthalmol 2008; 10 Suppl 1:78-87. [PMID: 17973838 DOI: 10.1111/j.1463-5224.2007.00563.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVE To measure changes in the thickness of the retinal nerve fiber layer in normal and early glaucomatous dogs with scanning laser polarimetry. ANIMALS STUDIED A total of 45 eyes, 32 normal and 13 glaucomatous eyes, of American Cocker Spaniels with primary glaucoma were used. All eyes were evaluated through a complete neuro-ophthalmic examination, tonometry, gonioscopy, slit-lamp biomicroscopy, and indirect ophthalmoscopy prior to enucleation. METHODS The retinal nerve fiber layer thickness was measured in anesthetized animals with scanning laser polarimetry (Nerve fiber analyzer, GDx; Laser Diagnostic Technologies, LTD, San Diego, CA, USA). Glaucomatous eyes retained some vision at the time of this study. RESULTS The mean +/- SD of the retinal nerve fiber layer thickness was 141.69 +/- 18 microm for normal dogs and 105.08 +/- 23.86 microm for visual glaucomatous dogs. The average retinal nerve fiber layer thickness in the superior and inferior retinal quadrants was 148.03 +/- 8.5 and 141.06 +/- 8.73 microm, respectively, for normal dogs, and 106.61 +/- 25.77 and 107.08 +/- 24.99 microm in the superior and inferior retinal quadrants, respectively, for glaucomatous dogs. The superior to nasal retinal nerve fiber layer thickness ratio was 1.45 for normal dogs and 1.26 for visual glaucomatous dogs. CONCLUSIONS Using scanning laser polarimetry it was possible to detect changes in retinal nerve fiber layer thickness in glaucomatous dogs at early stages of the disease. Therefore, this instrument has the potential to improve the clinical management of canine glaucoma by detecting progressive changes to the retinal nerve fiber layer.
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Affiliation(s)
- Gustavo A García-Sánchez
- Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, México City, Mexico.
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Sapienza JS, van der Woerdt A. Combined transscleral diode laser cyclophotocoagulation and Ahmed gonioimplantation in dogs with primary glaucoma: 51 cases (1996-2004). Vet Ophthalmol 2005; 8:121-7. [PMID: 15762925 DOI: 10.1111/j.1463-5224.2005.00356.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
OBJECTIVE To evaluate the combined diode laser cycloablation procedure and adjunctive Ahmed gonioimplant use in dogs with primary glaucoma. DESIGN Retrospective study. ANIMALS 48 dogs, 51 eyes with primary glaucoma. PROCEDURE Medical records from two large private clinical ophthalmology services were reviewed. Signalment, duration of glaucoma, gonioscopic evaluation, laser power and duration settings, immediate postoperative and final intraocular pressure and visual results, short and long-term visual outcome, and surgical complications were recorded. RESULTS The age range of affected dogs was 3.0-14.0 years, with a mean age of 7.5 +/- 2.6 years. Eleven pure breeds were represented, with the most common being the American Cocker Spaniel. The sex distribution was 22 neutered males, 1 intact male, 23 spayed females, and 2 intact female dogs. The right eye was affected in 33 cases, and the left eye in 18 cases. The average total joules, which was administered with the diode laser, was 109.6 +/- 23.6 J. Immediate surgical complications included fibrin formation in the anterior chamber (15), corneal ulcers (4), hyphema (7), and focal retinal detachment (1). Long-term complications included cataract formation (8 total, 2 of which were significant, vision-threatening), elevated intraocular pressure (IOP) (6), unstable gonioimplant (1), and glaucoma recurrence (14). Additional surgeries performed on the eyes over the course of study included: intrascleral prosthesis (4), enucleation (1), resection of fibrotic scar tissue (5), and repeat laser cycloablation (8). The dogs were examined for a mean follow-up time of 17.6 months (range: 2-83 months postoperatively). Twenty-nine cases were followed greater than one year. Vision was maintained in 42/51 eyes (82%) in the immediate short-term of this study. In all cases included in the study, good control of IOP was achieved in 39/51 (76%) of eyes, and IOP was poor or uncontrolled in 12/51 (24%) of eyes. Twenty out of 41 eyes (49%) maintained fair to excellent vision six months after surgery. Twelve months postoperative observations demonstrated that 12/29 (41%) of the eyes were still visual. CONCLUSIONS In primary glaucoma, the combined procedure of laser diode cyclophotocoagulation and Ahmed valve implant was associated with return or maintenance of vision in 42/51 eyes (82%) in the immediate short-term of this study, and a long-term IOP control in 39/51 (76%) of the cases, with 12/29 eyes (41%) visual after 12 months.
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Affiliation(s)
- John S Sapienza
- Long Island Veterinary Specialists, 163 South Service Road, Plainview, NY 11803, USA.
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Pugliese M, Carrasco JL, Geloso MC, Mascort J, Michetti F, Mahy N. Gamma-aminobutyric acidergic interneuron vulnerability to aging in canine prefrontal cortex. J Neurosci Res 2004; 77:913-20. [PMID: 15334609 DOI: 10.1002/jnr.20223] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The aged dog is considered a promising model for examining molecular and cellular processes involved in a variety of human neurological disorders. By using the canine counterpart of senile dementia of the Alzheimer's type (ccSDAT), we investigated the specific vulnerability of the gamma-aminobutyric acid (GABA) cortical subset of interneurons, characterized by their calcium-binding protein content, to neuronal death. Dogs representing a large variety of breeds were classified into three groups: young control, aged control, and ccSDAT. In all dogs, the general distribution and cell typology of parvalbumin-, calretinin-, and calbindin-positive neurons were found to be similar to those in the human. As in Alzheimer's disease patients, neurons displaying parvalbumin or calretinin immunoreactivity were resistant and the calbindin-positive ones depleted. Together with aging, amyloid deposition in its early phase (stage II) participates in this specific neuronal death, but with a lower potency. In conclusion, our data provide evidence that preservation of GABAergic cortical interneurons has to be focused on the early stage of beta-amyloid deposition. We also demonstrate the usefulness of dogs of all breeds for investigating the early phases of human brain aging and Alzheimer's disease.
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Affiliation(s)
- M Pugliese
- Unitat de Bioquímica, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain
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Cull G, Cioffi GA, Dong J, Homer L, Wang L. Estimating normal optic nerve axon numbers in non-human primate eyes. J Glaucoma 2003; 12:301-6. [PMID: 12897574 DOI: 10.1097/00061198-200308000-00003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE The goal of the present study is to develop a semi-automated method to estimate accurately, with minimum variance, the total number of axons by counting a subset of the axons within a primate optic nerve. METHODS Using an imaging analysis system, axons in 50% of the area of cross-sections of the retrobulbar optic nerve from five adult Rhesus monkeys were counted and extrapolated as an estimate of total axon number of the optic nerves. Both neural and non-neural areas were sampled. With the coordinates of the counts topographically registered, axon numbers within areas ranging from 1 to 50% were resampled. A Monte Carlo and theoretical estimate of the standard deviation of the total axon count for each sampled area was computed. RESULTS The mean cross-sectional area of the five optic nerves counted was 7.26 +/- 0.6 mm2, and the mean total axon count of the optic nerve area was 1,304,8168 +/- 89,112. When sampling less than 8% of the optic nerve, the standard deviation within the individual of the total estimated axon number increased sharply. CONCLUSION With this technique, the variance within each individual increased only slightly when the counting area was reduced from 50 to 8%, but increased sharply when the counted area became less than 8%. While counting less than 8% of the optic nerve area gives a good estimation of total axon count, the effect of a substantial increase in the standard deviation on the statistical power needed to differentiate group differences will depend on the study design.
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Affiliation(s)
- Grant Cull
- Discoveries in Sight, Devers Eye Institute, Portland, OR, USA
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Gelatt KN, Miyabayashi T, Gelatt-Nicholson KJ, MacKay EO. Progressive changes in ophthalmic blood velocities in Beagles with primary open angle glaucoma. Vet Ophthalmol 2003; 6:77-84. [PMID: 12641848 DOI: 10.1046/j.1463-5216.2003.00273.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To measure changes in the ocular and orbital blood flow velocities by color Doppler imaging (CDI) in beagles with primary open angle glaucoma as the disease progressed from early to advanced stages. METHODS CDI measurements were performed periodically on 13 glaucomatous Beagles during the nontreated mild, moderate and advanced stages of POAG over the course of 4 years. CDI was performed with the dogs lightly anesthetized (butorphanol 0.1 mg/kg IV, acepromazine maleate 0.02 mg/kg IV, and atropine sulfate 0.05 mg/kg) while the CD transducer was placed directly on the cornea anesthetized with 0.5% tetracaine hydrochloride. Intraocular pressure (IOP) by pneumatonography or TonoPen XL, heart rate and mean arterial blood pressure were measured at the beginning, middle and end of each study. The ophthalmic vessels examined included: external ophthalmic arteries and veins, long and short posterior ciliary arteries, anterior ciliary arteries and veins, primary retinal arteries, and vortex veins. Recordings of each vessel included peak systolic velocity (PSV), end diastolic velocity (EDV) and time averaged velocity (TAV), and when possible the resistive index (RI) and pulsatility index (PI) were computed. RESULTS CDI abnormalities were present before intraocular pressure exceeded the normal range. As the animals aged, and the glaucoma progressed with higher levels of IOP, significant changes occurred in nearly all vessels, and generally included a major increase in RI (P < 0.001) and an increase in the PI (P < 0.001). Mean arterial blood pressure (105 +/- 18 mmHg) and heart rate (118 +/- 33/min) remained reasonably constant. The IOP gradually increased as the disease progressed (early and normotensive: 19.4 +/- 3.9 mmHg; moderate: 29.7 +/- 2 mmHg; and advanced: 44.5 +/- 6 mmHg). The ocular veins seemed most influenced early on in the disease. Late in the disease, ocular venous blood flow could not be consistently demonstrated. An increase in the PI of ocular veins occurred in the moderately and severely affected glaucomatous Beagles. As the IOP increased, there were trends of increasing resistive index and pulsatility index in most arteries, and periods of marked decreased velocities of the vortex and external ophthalmic veins in severe cases. CONCLUSION CDI measurements in Beagles with primary open angle glaucoma during the course of 4 years indicate easily measurable and repeatable progressive blood flow abnormalities before the elevation of IOP and, thereafter, with gradually increased levels of IOP.
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Affiliation(s)
- K N Gelatt
- Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville 32610-0126, USA.
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Whiteman AL, Klauss G, Miller PE, Dubielzig RR. Morphologic features of degeneration and cell death in the neurosensory retina in dogs with primary angle-closure glaucoma. Am J Vet Res 2002; 63:257-61. [PMID: 11843127 DOI: 10.2460/ajvr.2002.63.257] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To investigate cellular death in the neurosensory portion of the retina during the first 7 days after onset of clinical signs of overt primary angleclosure glaucoma (PACG) in dogs. SAMPLE POPULATION 14 globes from dogs with PACG and 2 normotensive globes from dogs with PACG in the opposite eye. PROCEDURES Retinas were examined via light microscopy and terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick end-labeling. RESULTS Necrosis of ganglion cells and segmental degeneration of the nerve fiber layer rapidly progressed to scattered full-thickness retinal attenuation and disorganization. Apoptosis was detectable within 1 day after onset of PACG and was prominent by 3 days. Necrosis of ganglion cells was significantly greater in retinas affected for < or = 1 day, compared with retinas affected for > 1 day. In contrast, apoptosis in the ganglion cell layer was significantly greater in retinas affected for > 1 day, compared with retinas affected for < or = 1 day. End-stage retinal atrophy was seen by day 7. CONCLUSIONS AND CLINICAL RELEVANCE The presence of necrotic ganglion cells within 1 day after onset of clinical signs suggests a narrow window of opportunity to initiate effective therapy in overt PACG. Photoreceptor death is an important and striking aspect of neurosensory retinal degeneration after acute onset of PACG.
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Affiliation(s)
- Amanda L Whiteman
- Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison 53706, USA
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Brooks D, Komàromy A, Källberg M. Comparative optic nerve physiology: implications for glaucoma, neuroprotection, and neuroregeneration. Vet Ophthalmol 2001; 2:13-25. [PMID: 11397239 DOI: 10.1046/j.1463-5224.1999.00048.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The axoplasm of optic nerve axons moves bidirectionally at various speeds along an intra-axonal pressure gradient from the retinal ganglion cell (RGC) somata toward its synapse, and from the synapse towards the RGC somata. The axoplasmic flow of optic nerve axons is precarious even at normal intraocular pressures (IOP) as it moves from the intraocular optic nerve through the scleral lamina cribrosa to the intraorbital optic nerve. The scleral lamina cribrosa is not simply a porous region of the sclera but a specialized extracellular matrix of the central nervous system whose movement during fluctuations in IOP can affect optic nerve axoplasmic flow. The abundant optic nerve blood supply maintains adequate optic nerve head perfusion through a process of vascular autoregulation. Glaucoma is associated with reduced optic nerve axoplasmic flow and compromised optic nerve circulation such that RGC death due to glutamate excitotoxicity and neurotrophin deprivation result.
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Affiliation(s)
- D.E. Brooks
- University of Florida, PO Box 100126, Gainesville, FL 32610, USA
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Gelatt-Nicholson K, Gelatt K, MacKay E, Brooks D, Newell S. Comparative Doppler imaging of the ophthalmic vasculature in normal Beagles and Beagles with inherited primary open-angle glaucoma. Vet Ophthalmol 2001; 2:97-105. [PMID: 11397249 DOI: 10.1046/j.1463-5224.1999.00064.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The objective of this study was to compare orbital and ocular vasculature velocity, measured by Doppler imaging, in normal Beagles and Beagles with inherited primary open-angle glaucoma. Eight normal Beagles and 13 Beagles with different stages of primary open-angle glaucoma were evaluated twice with a 2-4-week period between measurements. Doppler imaging was performed with the dogs anesthetized, and the Doppler transducer applied directly on the corneal surface. The majority of the orbital vasculature (external ethmoidal artery; internal ophthalmic artery and vein; and external ophthalmic artery and vein) and ocular blood vessels (anterior ciliary artery and veins; long posterior ciliary arteries; short posterior ciliary arteries; primary retinal arteries; and the vortex veins) were identified and Doppler blood velocity parameters were determined. The glaucomatous dogs demonstrated significant differences in the Doppler velocity parameters of several orbital vessels (external ethmoidal, external ophthalmic, and internal ophthalmic arteries), and several ocular vessels (anterior ciliary, short posterior ciliary, and long posterior ciliary arteries). These differences included decreased blood velocities, and increased pulsatility and resistive indexes. The Doppler blood flow velocities of the primary retinal arteries were unchanged between the normal and glaucomatous dogs. In the glaucomatous dogs, the Doppler imaging suggests increased vascular resistance downstream in both the orbital and ocular vasculature. These blood velocity parameter changes may be primary or secondary, and may offer therapeutic opportunities to increase perfusion, prolong the retina and optic nerve head function, and maintain vision in the canine glaucomas.
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Affiliation(s)
- K.J. Gelatt-Nicholson
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN 55108 USA; Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0126, USA
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Abstract
The optic nerve is divided in four regions: intraocular, intraorbital, intracanalicular, and intracranial. The vertebrate retinal ganglion cells are classified by morphology, physiology and soma size. Species differences and similarities occur with retinal ganglion cells. Alpha retinal ganglion cells have large somata, large dendritic fields, large-diameter axons, and are most dense in the peripheral retina. Beta retinal ganglion cells have smaller diameter somata, smaller dendritic fields, small diameter axons, and predominate in the central retina. Gamma retinal ganglion cells are a heterogenous class of cells and have small diameter axons, and slow axon conduction velocities. The spatial distribution and organization of the retinal ganglion cells extends retinotopically through the nerve fiber layer, optic nerve, optic chiasm, optic tract, lateral geniculate nucleus, and visual cortex. The retinal nerve fiber layer thickness decreases from the optic disk toward the periphery of the retina. The retrobulbar optic nerve axon counts and axon density vary by species, with larger nerves having higher axon counts. Decussation of the optic nerve axons at the optic chiasm varies with 100% decussation in most birds and fish, 65% in cats, 75% in dogs, 80-90% in large animals, and 50% in primates. Centrifugal axons also occur in the optic nerve and may represent a method by which the brain can influence retinal activity.
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Affiliation(s)
- D.E. Brooks
- University of Florida, PO Box 100126, Gainesville, FL 32610, USA
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Vorwerk CK, Gorla MS, Dreyer EB. An experimental basis for implicating excitotoxicity in glaucomatous optic neuropathy. Surv Ophthalmol 1999; 43 Suppl 1:S142-50. [PMID: 10416757 DOI: 10.1016/s0039-6257(99)00017-x] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Most therapy for glaucoma is directed at the management of the intraocular pressure (IOP). Conventional wisdom holds that excessive pressure within the eye leads to the ganglion cell loss/optic nerve damage seen in this disease. Both glutamate and elevated IOP can selectively damage the retinal ganglion cells in the mammalian eye. We have identified an elevated level of glutamate in the vitreous humor of glaucoma patients (27 microM as compared to 11 microM in the control population). This concentration of glutamate suffices--on its own--to kill retinal ganglion cells. It is plausible that the IOP may represent an initial insult that precipitates the production of excessive glutamate. Therefore, even if glutamate elevation is an epiphenomenon associated with the course of the disease, it may contribute to ganglion cell loss in humans. Lowering the IOP may slow down glutamate production, but if nothing is done to block the toxic effects of glutamate as well, visual loss may result despite excellent IOP control. If interventions can be found to retard the production or toxic effects of glutamate, it may be possible to slow glaucomatous visual loss.
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Affiliation(s)
- C K Vorwerk
- Scheie Eye Institute and Philadelphia Veterans Administration, Department of Ophthalmology, University of Pennsylvania, 19104, USA
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Svoboda KK, Gong H, Trinkaus-Randall V. Collagen expression and orientation in ocular tissues. Prog Polym Sci 1998. [DOI: 10.1016/s0079-6700(97)00038-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Hof PR, Bogaert YE, Rosenthal RE, Fiskum G. Distribution of neuronal populations containing neurofilament protein and calcium-binding proteins in the canine neocortex: regional analysis and cell typology. J Chem Neuroanat 1996; 11:81-98. [PMID: 8877597 DOI: 10.1016/0891-0618(96)00126-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Neurophysiological experiments in carnivores have revealed the existence of a large number of cortical regions and an organization of sensory systems quite similar to that found in primates. However, the cyto- and chemoarchitecture of the cerebral cortex is relatively poorly known in carnivores. We analyzed the distribution and typology of classes of neurons containing neurofilament protein or the calcium-binding proteins parvalbumin, calbindin, and calretinin in six neocortical regions of the dog. In all these areas, neurofilament protein was present in a subpopulation of medium-to-large size pyramidal neurons predominantly distributed in layers III and V. Parvalbumin was present in a large population of morphologically diverse interneurons. Small ovoid and multipolar neurons were observed throughout the cortical layers, but predominated in layers II and IV. Layers III and V-VI were characterized by the presence of larger and intensely immunoreactive neurons with bitufted or multipolar morphology, and layers V-VI also contained large multipolar neurons. Calbindin was observed in small round and multipolar interneurons in layer II, and typical double bouquet cells in layer III. Layers IV-VI contained isolated double bouquet cells and large multipolar neurons. A few calbindin-immunoreactive pyramidal neurons were also observed in layer V. Calretinin was localized in bipolar and double bouquet cells in layers II and upper III. The lower part of layer III and layers IV-VI contained rare calretinin-immunoreactive neurons. In some areas, layer III displayed a few large isolated multipolar neurons and pyramidal neurons containing calretinin. In addition, the results show that there is a substantial degree of variability in the distribution of these proteins among cortical regions, and that although they are found in morphologically comparable neuronal types in dog, monkeys, and humans, many differences exist in their regional distribution patterns between carnivores and primates.
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Affiliation(s)
- P R Hof
- Fishberg Research Center for Neurobiology, Mount Sinai School of Medicine, New York, NY 10029, USA.
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