The association between refractive errors and cataract: the tehran eye study

To determine the association between refractive errors and different types of cataract in Tehran, Iran.

In a cross-sectional survey with a stratified cluster sampling approach, refractive errors were tested under cycloplegia. Myopia and hyperopia were defined as a spherical equivalent refractive error <-0.5 diopters (D) and more than +0.5 D, respectively. Cataract was graded according to the Lens Opacities Classification System III classification and the association between refractive errors and cataract was assessed. Of 1434 participants over the age of 40 years who participated in the study, data from 1313 right eyes were analyzed.

The mean age of the participants was 52.7 ± 10.0 years, and 58.3% (n = 767) were female. Overall, myopia was more prevalent among those with cataract (odds ratio [OR]: 2.00, 95% confidence interval [CI]: 1.38-2.89). Based on the type of cataract and refractive errors, the odds of myopia was significantly higher with nuclear cataracts (OR: 1.81, 95% CI: 1.14-2.87). The odds of myopia was higher for cases of nuclear cataract with some degrees of posterior subcapsular cataract (PSC) (OR: 3.33, 95% CI: 1.42-7.80). Of nine participants with cortical cataract, seven participants had hyperopia (OR: 3.77, 95% CI: 0.78-18.31).

Individuals with nuclear and PSC showed a significantly higher prevalence of myopia while the prevalence of hyperopia was lower in those with cataract. High myopia was seen in higher grades of nuclear cataract. The high percentage of hyperopia was also significant in patients with cortical cataract. More studies are necessary to clarify the correlation between cortical cataract and hyperopia.