# Spontaneous refractive error, ocular biometry and age related lens changes in a population of geriatric rhesus macaques

## TL;DR

This study examines eye health in elderly rhesus macaques, finding that most have hyperopia and lens changes typical of aging.

## Contribution

The study provides new reference values for refractive error and ocular biometry in geriatric rhesus macaques.

## Key findings

- Hyperopia was the most common refractive error in geriatric rhesus macaques.
- Median nuclear sclerosis grade was 1, indicating age-related lens changes.
- Reference values for ocular biometry were established for this population.

## Abstract

The purpose of this investigation was to determine refractive error, ocular biometry and age-related lens changes in a population of geriatric rhesus macaques (Macaca mulatta) from the California National Primate Research Center (CNPRC). Ophthalmic examination was performed in 182 rhesus macaques \documentclass[12pt]{minimal}
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\begin{document}$$\:\ge\:$$\end{document} 19 years of age using a cross-sectional study design, including streak retinoscopy, anterior segment tomography, A-scan ultrasound biometry and handheld slit lamp biomicroscopy. Median spherical equivalent refractive error was + 0.75 D with an interquartile range (IQR) of 0 to 1 D. Most eyes were hyperopic (n = 102, 55%) or emmetropic (n = 68, 36%); myopic eyes were the least common (n = 17, 9%). Anisometropia was present in 13 subjects (14%). Mean (± SD) corneal curvature was 52.6 ± 2.6 D (n = 79). Mean (± SD) axial globe length was 20.2 ± 1.5 mm, anterior chamber depth was 3.7 ± 0.4 mm, lens thickness was 4.1 ± 0.4 mm, and vitreous chamber depth was 12.2 ± 1.0 mm (n = 86). Median (IQR) nuclear sclerosis grade (n = 191, 98%) assessed with the lens opacities classification system II was 1 (1–2). Hyperopia is the most common refractive error in the geriatric rhesus macaque population at CNPRC. This study provides reference values for an isolated geriatric rhesus macaque population and broadens our understanding of refractive error and lens opacities in geriatric rhesus macaques which may serve as a model for studying novel therapeutics for refractive errors and cataracts.

The online version contains supplementary material available at 10.1038/s41598-025-30581-6.