Visual Factors Related to the Effect of Hyperopia on Reading Speed

Abstract

【Purpose】This study aimed to clarify the visual factors related to the effect of hyperopia on reading speed. By simulating hyperopia, we investigated the changes in reading speed and their relationship with visual functions and subjective symptoms.

【Subjects and Methods】Twenty-nine healthy young adults aged 19-24 participated in this study. Reading speed, visual functions, and fatigue-related subjective symptoms were assessed under two conditions: with full refractive correction and 2 diopters of simulated bilateral hyperopia. Reading speed was measured using MNREAD-J (iPad version). The rate of change in reading speed was defined as the average reading speed with hyperopia divided by the average reading speed with full refractive correction. Visual function tests for near visual acuity, accommodative gain during fixation of a near target for 90 seconds, near stereoacuity, near horizontal heterophoria, and near point of convergence were performed. Changes in visual functions and subjective symptoms were assessed based on the difference between the measurements with full refractive correction and simulated hyperopia.

【Results】The rate of change in reading speed ranged from 0.74 to 1.28. A significant negative correlation was found between the rate of change in reading speed and the amount of change in accommodative gain (r_s = －0.40, p = 0.03) . The rate of change in reading speed did not show any relationship with near visual acuity, near stereoacuity, near horizontal heterophoria, near point of convergence, or subjective symptom score.

【Conclusion】The results suggest that the decreased reading speed observed under hyperopia is related to the decline in the accuracy of the sustained accommodative response.