Choroidal Features of Cynomolgus Macaques in Relation to Age and Axial Length.

Purpose: The choroid plays a crucial role in myopia development, but related non-human primate studies are limited. We aimed to establish a reference standard for choroidal parameters and explore the relationship between refractive development and choroidal structure in cynomolgus macaques. Methods: Using macular enhanced-depth imaging optical coherence tomography images from cynomolgus macaques aged one to 28 years, we analyzed subfoveal choroidal thickness (ChT), choroidal luminal area (LA), stromal area (SA), total choroidal area (TCA), and choroidal vascularity index (CVI). Spherical equivalent, axial length (AL), intraocular pressure, and body weight were also recorded. We used generalized linear models to examine the associations of choroidal parameters with age and AL, and analyzed the interaction effect between these two variables. Restrictive cubic spline and piecewise regression analyses were conducted to identify potential breakpoints and perform stratified analyses. Results: Overall, 295 eyes of 295 macaques were analyzed. Macaques with high myopia exhibited smaller TCA, LA, CVI, and ChT. AL had a pronounced effect on reduced LA, SA, CVI, and ChT in adult stages but showed minimal influence during juvenile stages. Critical breakpoints were identified at 18.50-18.53 mm for LA, SA, and ChT, whereas CVI demonstrated a lower threshold (17.39 mm), suggesting its role as a sensitive early indicator of choroidal adaptation. Conclusions: The cynomolgus macaque is a valuable translational model for human refractive maturation, enabling the study of choroidal compensation and critical developmental transitions. These findings provide insights into choroid-associated mechanisms of myopia progression and complications, offering a foundation for developing targeted therapeutic interventions.