Ischemic model of optic nerve injury

(95.3%) of the 43 study eyes had evidence of vitreous detachment from the perifoveal macular region and the remaining tow eyes had complete PVD. When measurable, the size of the vitreomacular adhesion varied by diagnosis. Of 31 eyes with perifoveal vitreous detachment see in follow-up, only three (9.7%) showed progression to complete PVD over an average preoperative or total follow-up period of 30.0 months (range, 2 to 237 months). Surgical or spontaneous separation of the residual vitreomacular adhesion in 16 eyes was followed in 15 (93.8%) by partial or complete resolution of the symptoms and signs of macular traction. Age-related PVD appears to be an insidious, chronic event that begins in the perifoveal macula and evolves over a prolonged period of time prior to vitreopapillary separation. Though usually symptomatic, its early (perifoveal) stages may be complicated by one of several macular pathologies, determined in part by the size of the residual vitreomacular adhesion.— Author’s Abstract *M. W. Johnson, Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, Michigan.

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Ischemic model of optic nerve injury. Cioffi GA.* Trans Am Ophthalmol Soc 2005;103:592– 613.

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neuropathy. Ischemic optic neuropathy was induced by delivering endothelin-1 (ET-1) to the retrobulbar space in one eye of 12 primates for 6 to 12 months. Regional ganglion cell axonal sizes and densities were compared with the normal, contralateral eyes. Without changes of intraocular pressure, mean axonal density was significantly decreased in ET-1 eyes compared to controls (P ⫽ .03, paired t test). Two-way matched-pair analysis of variance showed a significant effect of ET-1 on overall axonal density (P ⬍ .0001). Among the animals with significant axonal loss, the mean axonal loss was 11.6%, and loss varied from 4% to 21%. Axonal loss was commonly localized within specific quadrants. Five animals were examined for preferential axonal size loss. As a group, there appears to be a tendency toward preferential large axonal loss, but the mean axonal loss of large and small axons did not meet significant differences (P ⫽ .1). However, examination of individual animals with significant loss shows significantly greater loss of large axons as compared to the small axons in three of the animals. Chronic optic nerve ischemia causes demonstrable and localized damage of the optic nerve, without intraocular pressure elevation. There is preferential loss of large retinal cell axons in animals with significant axonal loss. Ischemia-induced focal axonal loss is similar to human glaucoma and may represent a differential regional vulnerability.—Author’s Abstract

T IS PROPOSED THAT THE ANTERIOR OPTIC NERVE IS

specifically susceptible to microcirculatory compromise contributing to the development of glaucomatous optic

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*G. A. Cioffi, GA Devers Eye Institute, Portland, Oregon.

ABSTRACTS

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