Abstract
Purpose :
The subjective amplitude of accommodation is reportedly larger by binocular viewing compared with monocular viewing condition (Duane 1912). However, the difference is not well investigated by objective measurement. In this study, we investigated the difference of accommodative response objectively between monocular and binocular viewing condition using binocular wavefront sensor.
Methods :
Thirty five subjects (21-57 years, average 35.2 years) were examined. We switched the external fixation target stepwise from far (5 m) to near (0.5 m) and measured the accommodative response (spherical equivalent (SE), higher-order aberration (HOA)) and pupil diameter (PD) continuously at 30 frames/sec for 10 seconds under binocular or monocular condition using custom-built binocular Shack-Hartmann wavefront sensor. In each trial, the changes of SE value (ΔSE) from baseline to steady state of accommodation (between 5 to 9 seconds after switching to the near target) was averaged. The ratio of binocular ΔSE (ΔSEb) to monocular ΔSE (ΔSEm) was also calculated. The change of PD (ΔPD) and that of HOA were measured and averaged at steady phase.
Results :
The ΔSEb was 1.00 ± 0.43 D (mean ± SD), which was significantly larger than ΔSEm 0.91 ± 0.44 D (P=0.02, Wilcoxon). The ΔSEb/ΔSEm increased with age (r = 0.35, p = 0.04, Pearson). The ΔPD significantly smaller by binocular condition than monocular condition (binocular; 5.36 ± 1.21 mm, monocular; 5.83 ± 1.11mm p <0.001, Wilcoxon). The change of coma or spherical aberration was not different between binocular and monocular condition.
Conclusions :
A significant increase of objective amplitude of accommodation was observed by binocular viewing compared with monocular viewing condition, which may be due to the contribution of convergence accommodation in binocular condition. The significant decrease of pupil diameter in binocular condition may contribute to increase the pseudo-accommodation. The age dependent increase of ΔSEb/ΔSEm indicated the importance of binocular adjustment of glasses in early presbyopia.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.