Age-related macular degeneration in China: a population-based and clinical study

Background

Age-related macular degeneration (AMD) is one of the most common causes of irreversible blindness worldwide. We assessed its epidemiology and related factors in China.

Methods

Through population-based studies and clinical investigations, we assessed prevalence, incidence, and associated factors of AMD. The population-based investigations included several epidemiological surveys of ophthalmological and systemic diseases in China. The clinical studies consisted of biochemical examinations of aqueous humour samples obtained from patients undergoing intraocular surgery.

Findings

In the Beijing Eye Public Health Care Study, by use of a telemedicine approach, macular degeneration was identified to have caused visual impairment in 2700 (0·48%) of 562 788 elderly study participants (aged 55–85 years). In the Beijing Eye Study study, including 4439 participants and surveys done three times in 5-year intervals over a total period of 10 years, the prevalence of early AMD was 1·4%, late AMD was 0·20%, and exudative AMD was 0·10% per individual. Factors linearly association with AMD prevalence were older age (OR 1·06, 95% CI 1·04–1·08; p<0·0001), hyperopic refractive error (OR 1·16, 1·04–1·28; p=0·008), residence in a rural region (OR 0·33, 0·17–0·49; p<0·0001), and a lower level of education (OR 1·36, 1·07–1·65; p=0·01). The 5-year incidence of early AMD was 4·2% (SD 0·4, 95% CI 3·5–5·0), late AMD was 0·1% (SD 0·1, 0·0–0·2), and neovascular AMD was 0·1% (SD 0·1, 0·0–0·2). 5-year incidence was correlated with older age (odds ratio OR] 1·03, 95% CI 1·01–1·06; p=0·01) and hyperopic refractive error (OR 1·15, 1·03–1·33; p=0·03). In participants with exudative AMD, as compared with control participants, intraocular concentrations of intercellular adhesion molecule-1 (844 pg/mL SD 2073] vs 246 pg/mL SD 206]; p=0·001) and soluble vascular cell adhesion molecule-1 (7978 pg/mL SD 7120] vs 2999 pg/mL SD 1426]; p=0·001) were significantly elevated. The concentration of MCP-1 decreased (p=0·009) with the type of subfoveal neovascular membrane (classic membrane type, occult membrane, retinal pigment epithelium detachment; p=0·009). In control participants, as compared with patients with neovascular AMD, the concentration of vascular endothelial growth factor (VEGF) was correlated with significantly shorter axial length (r ?0·58; p=0·008).

Interpretation

Besides older age, hyperopic refractive error was the most important risk factor for prevalence and incidence of AMD in Chinese adults. The intraocular concentration of VEGF as a major AMD-associated growth factor decreased with increased axial length. The marked increase in myopia in the generation now aged younger than 30 years in China might be assumed to have a protective effect against AMD in the future.

Funding

National Natural Science Foundation of China.