Effect of proximity on the open-loop accommodative response of the eye

Abstract

We evaluated the relative contribution of proximal accommodation to the open loop accommodative response under open and closed loop conditions of vergence using 0.2 cycles per degree (c deg− 1) difference of Gaussian (DoG) targets at two test distances on five subjects. Accommodative responses were measured using a power refractor. Results show significant difference in the open loop accommodative response at the two distances under both open and closed loop conditions of vergence. Results obtained were applied to Hung and co-workers' [Investig. Ophthalmol. Vision Sci. 1991, 32, 2985–2991] proximal model of equations to find the relative contribution of proximal accommodation for the observed differences in the accommodative response. Results obtained show that the 0.2 c deg− 1 DoG stimulus at 0.4 m does not truly open the accommodation loop and the response obtained does have a significant level of proximal accommodation contribution. However, it can be used as a target to measure the relative changes in tonic accommodation and convergent accommodation responses and cannot be used for absolute measures when used at closer distances.