Nearwork-induced changes in lenticular thickness in different refractive groups

Abstract

Purpose The aim of this study was to directly measure lenticular thickness and its additivity after 1 and 2 hours of continuous reading at near in myopic and emmetropic young adults. Methods Thirty-five subjects consisting of 12 early-onset myopes, 11 late-onset myopes, and 12 emmetropes were tested. Axial lenticular thickness was measured in the right eye using A-scan ultrasonography before and immediately after 1 and 2 hours of continuous reading at near (35 to 40 cm). Results Group mean (±SD) changes in lenticular thickness from baseline values after the first and second hours of reading were 0.025 ± 0.011 and 0.035 ± 0.017 mm, respectively. The group mean increase in lenticular thickness after the second hour was significantly larger than after the first hour, with subsequent subgroup analysis indicating that this was found in the myopes only. Conclusion The lenticular increase was additive in nature, but only in the late-onset and early-onset myopes. This confirmed and extended objectively earlier studies that suggested increased nearwork accommodative susceptibility of a primarily lenticular nature in myopes.