Abstract: Objective To examine the ocular components to refraction of 2~5 years old rhesus monkeys and cynomolgus monkeys. Design Experimental study. Participants Twenty-four rhesus monkeys and 12 cynomolgus monkeys aged 2~5 years old. Methods Axial length (AXL), anterior chamber depth (ACD), lens thickness (LT),  vitreous chamber depth (VCD) and spherical equivalent (SE) were measured by A-scan ultrasonography and automatic computer optometry. A nonmydriatic fundus camera and optical coherence tomography were also performed to exclude ocular diseases. Normal distribution data was described as mean ± standard deviation and compared the two groups using t-test. Wilcox on Rank-Sum test was used to compare the continued non-normal distribution data, which was described as median (interquartile range). Given that data of both eyes of monkeys was used, linear mixed-effects model was used to adjust the inter-correlation between right and left eye. Main Outcome Measures SE, AXL, ACD, LT, VCD and correlation analysis between associated parameters and AXL. Results For 24 rhesus monkeys(48 eyes), the SE was (0.14±1.15) D, the AXL was 19.80 (19.18, 20.08) mm, the ACD was 3.65 (2.65, 3.84) mm, the LT was 3.93 (3.74, 4.19) mm, the VCD was 12.10±0.69 mm, there was no significant difference between both eyes (all P＞0.05). For 12 cynomolgus monkeys(24 eyes), the SE was(-0.46±0.96) D, the AXL was (18.11±0.54) mm, the ACD was (3.57±0.32) mm, the LT was (3.20±0.20) mm, the VCD was (11.34±0.48) mm, there was no significant difference between both eyes (all P＞0.05). The AXL of 48 rhesus and 24 cynomolgus monkeys’ eyes were included for linear mixed-effects model. The results of multiple stepwise regression analysis showed that the ACD, VCD, and weight were positively associated with a longer rhesus AXL (β=0.492, 0.572, 0.550, all P<0.05), while ACD and VCD were statistically significantly associated with a longer cynomolgus AXL (β=0.780, 0.876, both P<0.05). Conclusion We found that the ACD, VCD, and weight were positively associated with rhesus axial elongation and ACD and VCD were positively associated with cynomolgus axial elongation in the natural growth development conditions of Beijing, China. The ocular parameters could provide a foundation for future rhesus monkeys and cynomolgus monkeys research. (Ophthalmol CHN, 2022, 31: 349-354)

Key words: rhesus monkeys, cynomolgus monkeys, spherical equivalent, axial length