Appearance of the optic disk and retinal nerve fiber layer in atherosclerosis and arterial hypertension: an experimental study in rhesus monkeys

Abstract

PURPOSE: To evaluate changes in the appearance of the optic nerve head and retinal nerve fiber layer of rhesus monkeys with chronic arterial hypertension and atherosclerosis. METHODS: Color stereoscopic fundus photographs of 25 eyes of 25 rhesus monkeys (mean age ± SD of 20.4 ± 1.87 years) with chronic experimental systemic arterial hypertension and atherosclerosis (for a mean duration of 89.1 ± 39.1 months and 104.6 ± 62.2 months, respectively) were morphometrically evaluated. They were compared with color stereoscopic fundus photographs of 17 eyes of 17 normal monkeys (mean age ± SD of 19.76 ± 2.19 years) without any detectable systemic or ocular disease. There was no significant difference in age between the two study groups ( P = .22). RESULTS: In the atherosclerotic-arterial hypertensive group, visibility of the retinal nerve fiber layer was significantly (35.691 ± 5.95 units vs 28.72 ± 9.18 units, P = .009) less and frequency of localized retinal nerve fiber layer defects was significantly (six of 25 or 24% vs zero of 17 or 0%, P = .01) more than in the normal control group. The two groups did not differ significantly in size of the neuroretinal rim ( P = .66), shape of the neuroretinal rim ( P > .15), size of alpha ( P > .44) and beta ( P > .65) zones of parapapillary chorioretinal atrophy, or regional distribution of alpha and beta zones ( P > .40). CONCLUSIONS: Chronic experimental arterial hypertension and atherosclerosis do not markedly change the size and shape of the neuroretinal rim or parapapillary atrophy; however, they do lead to reduced visibility of the retinal nerve fiber layer, with localized retinal nerve fiber layer defects indicating optic nerve damage. Thus, unlike glaucomatous optic neuropathy, experimental arterial hypertension and atherosclerosis are not associated with a significant change in the parapapillary atrophy or the neuroretinal rim of the optic disk despite the loss of nerve fibers.