Refraction and Change in Refraction Over a 20-Year Period in the Beaver Dam Eye Study

Hyperopic shifts in refraction have been consistently reported in adults over 40, followed by myopic shifts after age 70. Although potential factors underlying these changes in refraction in older adults have been investigated previously, the studies were restricted by the limited longitudinal data available. The authors of this study sought to better characterize the long-term trajectory of refraction in older adults using 20 years of prospective data.

The impact of cohort effects on refraction over 20 years was examined. Generalized estimating equations were used to evaluate the etiologic factors underlying refraction and changes in refraction measured over a 20-year period (1988-2010) among adults over age 40 from the Beaver Dam Eye Study.

Only individuals with nuclear cataract experienced a myopic shift in refraction, showing a 0.25 diopter (D) decrease (95% confidence interval [CI]: -0.44 D to -0.07 D) over a five-year period. Individuals with mild and moderate nuclear sclerosis showed varying degrees of hyperopic shifts over five years (0.22 D: 95% CI: 0.20 D-0.25 D; 0.23 D: 95% CI: 0.20 D-0.27 D, respectively).

Nuclear cataract is the primary contributor to the myopic shift among older individuals. Birth cohort effects on baseline refraction but not change in refraction were observed.