[An epidemiological survey of visual impairment in rural populations aged 30 and above: the Handan Eye Study]

Objective: To investigate the changes in prevalence and causes of blindness and visual impairment over six years among rural populations aged 30 and above in Yongnian County, Handan City, Hebei Province, a pilot area in northern China for blindness prevention and treatment, and to study the incidence of common blinding eye diseases. Methods: This population-based prospective cohort study included a baseline survey conducted from 2006 to 2007 using stratified cluster sampling, targeting 6 830 Han Chinese individuals aged 30 and above, with a response rate of 90.4%, and a follow-up survey conducted from 2012 to 2013 with 5 394 participants, maintaining a response rate of 85.3%. Visual impairment was defined according to World Health Organization standards as visual acuity<20/60 but ≥20/400, and blindness as visual acuity<20/400. Age-and gender-standardized prevalence rates of blindness and visual impairment, along with their 95% confidence intervals (CI), were estimated. The six-year incidence rates of primary glaucoma, age-related macular degeneration, and myopic maculopathy, along with their 95%CI, were reported. Results: At baseline, the standardized prevalence of bilateral blindness in individuals aged 30 and above was 0.6% (41/6 799) for presenting visual acuity and 0.5% (31/6 799) for best-corrected visual acuity. These rates were higher than those found in the follow-up survey, 0.5% (27/5 293) and 0.3% (17/5 276). Conversely, the standardized prevalence of bilateral visual impairment increased from 4.7% (361/6 799) and 1.0% (85/6 799) at baseline to 6.5% (355/5 293) and 1.4% (74/5 276) at follow-up, respectively. The leading cause of bilateral blindness was cataract in both baseline (13/31, 41.9%) and follow-up (7/17) surveys. Other major causes included myopic retinal degeneration (5/31, 16.1% at baseline; 2/17 at follow-up), glaucoma (3/31, 9.7% at baseline; 2/17 at follow-up), and corneal opacity (3/31, 9.7% at baseline; 2/17 at follow-up). Over six years, the incidence rates for primary glaucoma, early and late age-related macular degeneration, and myopic maculopathy in individuals aged 35 and above were 1.6% (95%CI: 1.2%-1.9%), 4.2% (95%CI: 3.8%-4.7%), 0.2% (95%CI: 0.2%-0.3%), and 0.1% (95%CI: 0.0%-0.2%), respectively. Conclusions: The prevalence of bilateral blindness in the rural population of Yongnian County, Handan City, Hebei Province, decreased over six years due to blindness prevention and treatment efforts but remained higher than in urban areas. Meanwhile, the prevalence of bilateral visual impairment increased since the baseline survey. Cataracts continued to be the primary cause of blindness, followed by myopic retinal degeneration, glaucoma, and corneal opacity.