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GA Cioffi, L Wang, J Dong, G Cull; Regional Vulnerability of Axons in a Chronic Optic Nerve Ischemia Model in Primates . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2886.
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Purpose: To study the regional pattern of optic nerve (ON) axonal damage induced by chronic ischemia in a primate model. Methods: Chronic ON ischemia (4-6 mths) was induced by delivering Endothelin-1 via a subcutaneous osmotic minipump and delivery tube to the supero-nasal retrobulbar space in one eye of 8 (5 are analyzed at time of submission) adult rhesus monkeys (contralateral eyes as controls). In vivo topographic changes of optic disc were evaluated with Heidelberg Retinal Tomography (HRT, 4 eyes) and stereophotography. Total axonal counts and regional densities of ON cross-sections (2 mm behind globe) were quantified with a novel automated image analysis system in 4 and 8 pie-shaped regions. Results: Compared to controls, there was significant axon loss (20-40%, P<0.01) in most regions of the ischemic eyes. However, the axonal loss was not uniform, with the nasal ON regions (close to the site of endothelin-1 delivery) suffering less damage (stat signif, see figure) compared to the temporal ON, in all five animals. View OriginalDownload SlideView OriginalDownload Slide Final HRTs, compared to baseline, in the ischemic eyes showed significant increase in the cup area, cup volume and decrease in rim volume and retinal nerve fiber layer thickness. Conclusion: Chronic ON ischemia selectively causes axonal damage of the temporal ON in a primate model. This suggests a regional vulnerability of the ON, with increased susceptibility of the temporal ON with a chronic ischemic insult.
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