Clinicopathological correlation of parapapillary atrophy in monkeys with experimental glaucoma and temporary central retinal artery occlusion

Objective: To investigate the clinicopathological correlation of parapapillary atrophy. Materials and Methods: The study included 16 eyes of rhesus monkeys (Macaca mulatta) - 4 eyes with experimental glaucoma, 11 eyes after experimental temporary occlusion of the central retinal artery, and 1 normal eye. On histological sections, we measured zones with different histological characteristics. On fundus photographs, alpha zone and beta zone of parapapillary atrophy were measured and correlated with the histological data. Results: The size of the clinical alpha zone of parapapillary atrophy was significantly correlated with the size of the histological region with irregularities of the retinal pigment epithelium (P = 0.05; correlation coefficient r = 0.49) and with the size of the histological region with a decreased density of retinal photoreceptors (P = 0.01; r = 0.60). The size of clinical beta zone of parapapillary atrophy significantly correlated with the size of the histological region with complete loss of the retinal pigment epithelium (P < 0.001; r = 0.91), with the size of the histological zone with a complete loss of photoreceptors (P < 0.001; r = 0.81), and with the size of the histological zone with a closed choriocapillaris (P < 0.001; r = 0.89). Conclusions: The clinically seen alpha zone of parapapillary atrophy correlates with histological parapapillary irregularities of the retinal pigment epithelium and decreased density of retinal photoreceptors. The clinically seen beta zone of parapapillary atrophy correlates with histological complete loss of the retinal pigment epithelium and of the photoreceptors, and a closure of the choriocapillaris.