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Clay Holley, Nick Hogan; Comparative Ocular Anatomy & Age-Related Ocular Changes of the Western Lowland Gorilla. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3034.
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To evaluate age-related ocular changes of the Western lowland gorilla and how those compare to the human eye. To our knowledge, this is the first report of age-related ocular changes in this species.
Timbo, a 49 year old female Western lowland gorilla, died from anesthesia complications in August 2011. Her eyes were placed in formalin within 15 hours of her death. We took a standard horizontal approach to the left eye and a modified ora serrata approach to the right eye when dissecting the eyes. After taking photos of the gross specimens, we sent tissue for histological stains and reviewed these to complete our report of the findings.
Globe dimensions, extraocular muscle insertions, tendon widths, and corneal and scleral thicknesses are similar to humans. Timbo had previously had cataract surgery in both eyes, so the anterior portion of the lens capsule could not be evaluated. However, the posterior lens capsule is thicker in Western lowland gorillas (10 micrometers) than in humans (average of 4 micrometers). Timbo had several chorioretinal scars in both eyes, which could be age-related. The age-related changes found were very similar to those that are often found in human eyes. Notably, Timbo was found to have lattice degeneration, peripheral retinal atropy and microcystoid degeneration, cobblestone degeneration, and mild retinal vascular arteriosclerosis. In Timbo’s left eye, we found a significant area of geographic atrophy in the central macula that corresponded to the area that had been noted clinically on pre-operative exams during the planning for cataract surgery in 2009. This area appeared grossly much like the geographic atrophy seen in humans with age-related macular degeneration. One of Timbo’s eyes had peripheral optic nerve atrophy of unknown etiology that may be associated with the peripheral retinal degeneration seen greater temporally in that eye than in other peripheral quadrants. We also found corpora amylacea in periodic acid-Schiff (PAS) stains of the optic nerve and surrounding structures.
Lens capsule and supporting lens structures are similar to humans except that the posterior capsule is two to three times thicker, which would theoretically make cataract surgery on this subspecies somewhat more forgiving. Age-related retinal and optic nerve changes are remarkably similar to those found in humans.
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