Five-year refractive changes in an older population: the Blue Mountains Eye Study.

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.