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M.E. Guzowski, S. Fraser-Bell, E. Rochtchina, J. Wang, J. Wang, P. Mitchell; Asymmetric Refraction in an Older Population. Findings from the Blue Mountains Eye Study . Invest. Ophthalmol. Vis. Sci. 2003;44(13):798.
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Purpose:To describe the prevalence of anisometropia in an older Caucasian population and its relationship to cataract and other characteristics. Methods:The Blue Mountains Eye Study examined 3654 persons aged 49-97years. All participants underwent a comprehensive eye examination, including subjective refraction according to a modified ETDRS protocol and lens photography. Spherical equivalent (sum of sphere + half cylinder), in diopters (D) defined refractive error. Refractive asymmetry was assessed in phakic persons with measurable refraction in both eyes. Anisometropia was defined as at least 1.0D difference in spherical equivalent between the two eyes. Results:Anisometropia was observed in 501 (14.7%) phakic participants. Moderate anisometropia (>3.0D) in 2.1%. Mean refractive asymmetry for all ages was 0.55D. Mean refractive asymmetry in persons aged <60 years, 60-69, 70-79 and 80+ years was 0.43D, 0.51D, 0.72D and 0.88D, respectively. The prevalence and magnitude of refractive asymmetry increased with age, p<0.001 and with higher levels of ametropia and astigmatism. The following factors were associated with refractive asymmetry: increasing age (60% increased odds per decade), unilateral or bilateral cataract (two-fold odds) and increasing ametropia (16-fold and 4-fold odds for myopia and hyperopia, respectively). The highest prevalence of anisometropia was seen with moderate to high myopia. Phakic participants with anisometropia were more likely to have amblyopia (10.8%) and strabismus (11%) than participants without anisometropia (1.9%, 5.6%), p=0.001.Conclusions:This study provides data on the magnitude and distribution of refractive asymmetry in a representative older Australian community. Anisometropia is relatively common. It is associated with increasing age, presence of cataract and increasing cylindrical and spherical error (particularly moderate to high myopia). The well-reported associations of anisometropia with amblyopia and strabismus were confirmed.
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