Retinal and Choriocapillaris Thickness and Age in Macaques in Development and Aging

Nonhuman primates (NHPs) serve as valuable models for human retinal and choroidal diseases related with development and aging. This study aimed to investigate the association among age and thickness of the retina, RPE, and choriocapillaris in cynomolgus macaques. Association of age with choriocapillaris was examined in postmortem human samples.

Optical coherence tomography images were obtained from 543 eyes from 285 macaques aged 0.78 to 22.4 years. The association between age and thickness of retinal and subretinal layers were examined using piecewise linear mixed effects models. Choriocapillaris thickness was assessed microscopically in postmortem human globes from 24 individuals aged 11 to 82 years.

Before age 4 years (equivalent to 12 years in humans), total retinal thickness and ganglion cell layer, inner nuclear layer, and parafoveal outer nuclear layer thickness were positively associated with age, whereas after age 4 years, thicknesses of these layers were negatively associated. Age was negatively associated with retinal nerve fiber layer and foveal outer nuclear layer thickness, but positively with thicknesses of RPE/Bruch's membrane and choriocapillaris layers throughout the entire age range. Analysis of postmortem human specimens demonstrated a positive correlation between choriocapillaris diameter and age.

Cynomolgus macaques undergo thickening of multiple retinal layers through their juvenile stage. Afterward, macaques undergo thinning of multiple retinal layers with age, suggesting aging-related changes. The increase in choriocapillaris thickness with age in both macaques and humans suggest remodeling due to aging. Cynomolgus macaques represent a valuable NHP model for studying developmental- and aging-related retinal/subretinal changes.