Purchase this article with an account.
T.A. Cox, K.S. Naidoo, L.B. Ellwein, RESC Working Group; The Relationship Between Visual Acuity and Myopia in Children . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5615.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: The Refractive Error Study in Children assessed 40779 children between the ages of 5 and 15 years in eight population–based surveys in Nepal, China, India, South Africa, Chile, and Malaysia, using a standardized protocol. Previous papers have characterized separately the extent of refractive error and the distribution of visual acuity in these surveys. Here we examine the relationship between uncorrected visual acuity and refractive error. Methods: Visual acuity was measured at four meters using a retroilluminated logMAR chart with tumbling E optotypes. Refractive error was determined by autorefraction under cycloplegia. Myopia was defined as SE (spherical equivalent) <= –0.25, with best meridian <= 0. Eyes with high myopia (SE > –6) were excluded. Only eyes without other ocular disease were included in this study. Results: Data from 4934 myopic right eyes were analyzed. A curvilinear relationship was found between SE and logMAR acuity. A variety of nonlinear equations were evaluated, and the best fit was found with a quadratic equation that included interaction terms with cylinder strength. The coefficient of determination for this fit was 0.74; 43% of residuals were greater than 0.1 logMAR (one line), 16% were greater than 0.2 logMAR (two lines), and 5% were greater than 0.3 logMAR (three lines). Vision in eyes with against–the–rule astigmatism was about one letter worse on average. Age and gender also had minor effects on acuity. Conclusions: This study is the first to examine in detail the relationship between unaided visual acuity and refractive error in a large cohort since the work of Pincus (1946). Our data on the association between visual acuity and refractive error may prove helpful in the clinical assessment of patients unable or unwilling to provide accurate responses during visual acuity testing. However, there remains a significant amount of variation in visual acuity that is unexplained by our regression models. Some, but not all, of this variability can be attributed to intra–individual variation in visual acuity measurement.
This PDF is available to Subscribers Only