Purpose
To examine the causes of vision impairment (VI) among children referred for vision rehabilitation and to determine the relationship between refractive error and diagnosis.
Methods
Charts of all children seen for vision rehabilitation in a university-based low vision rehabilitation service between October 2005 and September 2012 were retrospectively reviewed. Children ages 2 to 18 whose records contained: date of birth, primary ocular diagnosis, visual acuity and refractive error were included. For children with more than one visit during that time period, only the baseline visit was used in this analysis.
Results
440 charts were abstracted and 377 met inclusion criteria. The most common etiology for vision impairment was albinism (17.2%) followed by optic atrophy (12.7%), retinal degeneration (9.8%), optic nerve hypoplasia (8.8%) and cortical vision impairment (5.8%). There was a wide range of refractive error (spherical equivalent (SE) OD -26.50 to +18.50 and OS -25.25 to +19.25). The SE was not normally distributed (Kolmogorov-Smirnov test, p<0.010). The mean SE was OD: -0.90 ±6.0 and OS: -0.70±5.9 and the median SE refractive error was plano OD and OS. Although the mean refractive error was small, 69.5% of right and 69.6% of left eyes had SE refractive error greater than ±1D (see figures 1 & 2). The range of astigmatism was from 0 to -6.00D OD and 0 to -8.00D OS. Astigmatism was common with 53% of right and 50% of left eyes having astigmatism ≥1D. There were no refractive trends associated with ocular diagnosis with the exceptions of the obvious diagnoses of high myopia and aphakia.
Conclusions
The diagnosis related to VI in this U.S. study is different than that found in other developing and developed countries as well as from that reported previously from a school for the blind in the same state. A multi-center study is necessary to better understand the epidemiology of childhood vision impairment. Children with VI in this sample have significant refractive error, with a leptokurtic distribution. Some studies have reported a normal distribution of refractive error among children with VI, suggesting that vision impairment interferes with emmetropization. Here, there is evidence for emmetropization in the presence of VI, however there are large tails to the distribution suggesting the mechanism for emmetropization may be less precise.
Keywords: 584 low vision •
676 refraction •
511 emmetropization