Purpose: To characterize the peripheral defocus of the monkey crystalline lens and its changes with accommodation.

Methods: Experiments were performed on 15 lenses from 11 cynomolgus monkey eyes (age: 3.8–12.4 years, postmortem time: 33.5±15.3 hours). The tissue was mounted in a motorized lens stretcher to allow for measurements of the lens in the accommodated (unstretched) and unaccommodated (stretched) states. A custom-built combined laser ray tracing and optical coherence tomography system was used to measure the paraxial on-axis and off-axis lens power for delivery angles ranging from− 20 to+ 20 (in air). For each delivery angle, peripheral defocus was quantified as the difference between paraxial off-axis and on-axis power. The peripheral defocus of the lens was compared in the unstretched and stretched states.

Results: On average, the paraxial on-axis lens power was 52.0±3.4 D in the unstretched state and 32.5±5.1 D in the stretched state. In both states, the lens power increased with increasing delivery angle. From 0 to+ 20, the relative peripheral lens power increased by 10.7±1.4 D in the unstretched state and 7.5±1.6 D in the stretched state. The change in field curvature with accommodation was statistically significant (P< 0.001), indicating that the unstretched (accommodated) lens has greater curvature or relative peripheral power.

Conclusions: The cynomolgus monkey lens has significant accommodation-dependent curvature of field, which suggests that the lens asserts a significant contribution to the peripheral optical performance of the eye that also varies with the state of accommodation.