Purpose: To examine 5-year changes in refractive error and astigmatism in an older population.
Design: Population-based cohort study.
Participants: The Blue Mountains Eye Study examined 3654 residents aged 49 years or older from 1992 to 1994. After excluding 543 persons who died since baseline, 2335 (75.1%) attended 5-year examinations from 1997 to 1999.
Methods: Both examinations included a detailed eye assessment, with subjective refraction performed according to a modified Early Treatment of Diabetic Retinopathy Study protocol.
Main outcome measures: Spherical equivalent (sum of sphere + cylinder) was used as the measure of refractive error. Only phakic eyes with best-corrected visual acuity >20/40 were included (n = 3701).
Results: Similar changes in refractive error were observed for the two eyes. Symmetric changes were found in 72% of participants when the difference between eyes was within 0.5 diopters (D) and in 91% when the difference was within 1.0 D. The 5-year change in spherical power was in a hyperopic direction for younger age groups and in a myopic direction for older subjects, P < 0.0001. The gender-adjusted mean change in refractive error in right eyes of persons aged 49 to 54, 55 to 64, 65 to 74, and 75 years or older at baseline was +0.41 D, +0.30 D, +0.05 D, and -0.22D, respectively. Refractive change was strongly related to baseline nuclear cataract severity; grades 4 to 5 were associated with a myopic shift (-0.33 D, P < 0.0001). Education level and age of onset of myopia, but not gender or diabetes, also predicted refractive change. The mean age-adjusted change in refraction was +0.14 D for hyperopic eyes, +0.32 D for emmetropic eyes, and +0.15 D for myopic eyes. The mean change in cylinder power over the 5-year period was small, irrespective of baseline refraction. The axis of astigmatism remained stable in most cases (64%), whereas 12% changed to "against the rule" and 11% to "with the rule."
Conclusions: This report has documented refractive error changes in an older population and confirmed reported trends of a hyperopic shift before age 65 years and a myopic shift thereafter associated with the development of nuclear cataract.