Purpose
To determine the prevalence of age-related macular degeneration (AMD) in a rural southwest island of Japan.
Methods
The study was a population-based, cross-sectional study conducted in 2005-2006. Of all the residents at the age of 40 or older in Kumejima island, a rural southwest island of Japan, 3762 subjects (response rate, 81.2%) underwent a detailed ocular examination. Fundus photographs using a digital retinal camera (TRC-NW7, Topcon, Tokyo, Japan) for the right eye were used for diagnosis of AMD. Wisconsin grading system was introduced to determine the crude prevalence of (1) early AMD defined as the presence of drusen with diameter of 125μm or larger or pigmentary abnormalities and (2) that of late AMD defined as the presence of neovascular AMD or geographic atrophy. Age-standardized prevalence was also estimated after direct age standardization to the world population reported by World Health Organization (WHO). Multivariate analysis was used to analyze the relationship between early or late AMD and possible risk factors such as age, gender, axial length, and history of cataract surgery.
Results
Thirty-five subjects were excluded for the lack of baseline data. Of the remaining 3561 subjects, 2651 (74.4%) had gradable photographs. They were significantly younger than those with ungradable photographs (57.6 vs. 72.5, P<0.0001). The crude prevalence of early and late AMD with 95% confidence interval were 14.3% (13.0-15.6) and 0.15% (0.00-0.30), respectively. Additionally, age-standardized prevalence were 13.3% (12.1-14.6) and 0.12% (0.00-0.24), respectively. Logistic regression analysis revealed that older age, male, shorter axial length, and history of cataract surgery (p=0.0001 to 0.03) were correlated with the presence of early AMD, and older age (p=0.020) with late AMD.
Conclusions
The prevalence of age-related macular degeneration (AMD) in a rural southwest island of Japan was estimated. Risk factors for early AMD were older age, male, shorter axial length, and history of cataract surgery,while that of late AMD was older age.