Changes in refractive status in an elderly Chinese population in a 7-year follow-up: The Shihpai Eye Study

Refractive error is the major cause of moderate and severe visual impairment. Visual impairment limits people's ability to perform daily tasks and affects their quality of life. Longitudinal data on the refractive status of the elderly was available only for whites and Africans. The purpose of this study was to report the 7-year incidence of myopia, hyperopia and refractive error change as well as their associated risk factors in a metropolitan elderly Chinese population.

The Shihpai Eye Study 2006 included 460/824 (55.8%) subjects (age range 72-94 years old) of 1361 participants in the 1999 baseline survey for a follow-up eye examination. Incidences were calculated for those who had emmetropia (-0.50D < spherical equivalent (SE) <+0.50D) at baseline. Refractive error change at 7 year was defined as (SE at the 7-year visit - SE at baseline).

90 (26.4%) subjects were emmetropic, 61 (17.9%) were myopic and 190 (55.7%) hyperopic. The mean refractive error was 0.49 ± 2.19 D and the average change in refractive error was -0.13 ± 1.03 D. The incidence of myopia at seven-year was 26.8 % [95% Confidence interval (C.I.): 22.8%-30.9%] and the incidence of hyperopia was 19.7% (95% C.I.: 16.1%-23.3%). Nuclear sclerosis (>Grade 2 vs. ≤Grade 2) [p < 0.0001; relative risk (RR): 8.94; 95% C.I.: 4.40-18.2], anterior chamber depth (mm) [p = 0.05; RR: 0.43; 95% C.I.: 0.18-1.01] and lens thickness (mm) [p < 0.01; RR: 2.35; 95% C.I.: 1.17-2.73] were significantly associated with myopic shift. On the other hand, hyperopic shift was significantly associated with cortical opacity (>Grade 2 vs. ≤Grade 2) (p = 0.02; RR: 1.21; 95% C.I.: 1.02-3.54).

In this elderly Asian population, there was on average a slight myopic shift. The incidence of myopia was comparable to population-based studies of other ethnic groups, whereas the incidence of hyperopia was substantially higher.