Abstract
Abstract: :
Purpose: It has been well documented by multiple longitudinal studies that cataract, especially nuclear sclerosis, may lead to myopia, but it is unclear whether myopia predisposes to cataract formation. Several cross–sectional studies have suggested that myopia is a risk factor for certain types of lens opacities, especially posterior subcapsular cataract. However, it can be difficult to determine the directionality of this relationship. The purpose of this population–based cross–sectional study is to use data such as age of first distance glasses wear and current refraction to establish a temporal relationship between the onset of myopia and lens opacity. Methods: Participants from the Salisbury Eye Evaluation, aged 65–84 years (n=2520), filled out questionnaires regarding medical history, social habits, and UV light exposure (including a detailed history of distance spectacle wear), and underwent a full ocular examination. Lens photographs were taken for assessment of lens opacity, using the Wilmer grading system. Multivariate logistic regression models were used to analyze the relationship between lens opacity type and degree of myopia while accounting for potential confounders. Results: Significant associations were found between myopia and both N and PSC opacities. For N, the odds ratios (ORs) were 2.25 for myopia between –0.50 diopters (D) and –1.99 D (p<0.001), 3.65 for myopia between –2.00 D and –3.99 D (p<0.001), 4.54 for myopia between –4.00 D and –5.99 D (p<0.001), and 3.61 for myopia > 6.00 D (p=0.002). For PSC cataracts, ORs were 1.59 for myopia between –0.50 D and –1.99 D (p=0.11), 3.22 for myopia between –2.00 D and –3.99 D (p=0.002), 5.36 for myopia between –4.00 D and –5.99 D (p<0.001), and 12.34 for myopia > 6.00 D (p<0.001). No association was found between myopia and cortical opacity. The association between PSC opacity and myopia was equally strong for those with glasses wear by age 21 than for those without; for N, higher odds ratios were found for myopes who started glasses wear after age 21. Conclusions: These results confirm the previously reported association with myopia and PSC, and suggest the myopia may precede the onset of PSC temporally. Measures of association between PSC and myopia were stronger in the current study than have previously been found, perhaps due to the older age of the population studied. The magnitude of this association suggests that the etiology whereby myopia may lead to PSC deserves further study.
Keywords: cataract • myopia • clinical (human) or epidemiologic studies: risk factor assessment