Susan J Leat1, Andrea Mohr. 1. School of Optometry, University of Waterloo, Waterloo, Ontario, Canada.
Abstract
PURPOSE: There are isolated reports that accommodative response is reduced in some populations with low vision. The purpose of this study was to measure accommodative response in a wider range of pre-presbyopes with visual impairment and to examine what factors may affect accommodation among the low vision population. METHODS: Accommodative responses for accommodative demands between 4 and 10 D were measured with dynamic retinoscopy in 21 subjects with low vision due to a variety of disorders and in 40 control subjects, aged 3 to 35 years. The control subjects were divided into age groups of 3 to 5, 6 to 10, 11 to 26, and 27 to 35 years, and the response of each subject with low vision was compared against the age-matched control group. The slope of the accommodative function and the mean error of the accommodative response were also calculated. RESULTS: Eighty-six percent of the subjects with low vision showed responses that were outside the 95% range of normal. The deficit increased with increasing accommodative demand. Reduced accommodation was not predicted by age, visual acuity, presence of nystagmus, refractive error or time of onset of the disorder. The results show that the accommodation errors are often greater than predicted by increased depth of focus due to poor visual acuity. CONCLUSIONS: It seems likely that accommodative response is based on many factors that may be present in an eye with low vision, which interact in a complex fashion.
PURPOSE: There are isolated reports that accommodative response is reduced in some populations with low vision. The purpose of this study was to measure accommodative response in a wider range of pre-presbyopes with visual impairment and to examine what factors may affect accommodation among the low vision population. METHODS: Accommodative responses for accommodative demands between 4 and 10 D were measured with dynamic retinoscopy in 21 subjects with low vision due to a variety of disorders and in 40 control subjects, aged 3 to 35 years. The control subjects were divided into age groups of 3 to 5, 6 to 10, 11 to 26, and 27 to 35 years, and the response of each subject with low vision was compared against the age-matched control group. The slope of the accommodative function and the mean error of the accommodative response were also calculated. RESULTS: Eighty-six percent of the subjects with low vision showed responses that were outside the 95% range of normal. The deficit increased with increasing accommodative demand. Reduced accommodation was not predicted by age, visual acuity, presence of nystagmus, refractive error or time of onset of the disorder. The results show that the accommodation errors are often greater than predicted by increased depth of focus due to poor visual acuity. CONCLUSIONS: It seems likely that accommodative response is based on many factors that may be present in an eye with low vision, which interact in a complex fashion.