To describe the prevalence of different refractive errors regarding their biological and environmental factors among elderly population living in Gilan Province, Iran in 2014.

In this population-based cross sectional study, 2975 individuals aged 50 years old or more living in both rural and urban regions (85 clusters) of Gilan province were selected by random cluster sampling. Ophthalmologists, optometrists, and the local health workers, who could obtain an acceptable agreement (Kappa coefficient >0.6) in a training course, conducted a comprehensive visual and ophthalmic examinations in the field. Myopia and hyperopia were defined as spherical equivalent (SE) of ≤-0.50D and SE ≥+0.50D, respectively and cylindrical power of <-0.50D was considered as astigmatism. The SE difference of 1.00D or higher between the two eyes of each individual was defined as anisometropia.

A total of 2587 out of 2975 individuals (response rate, 87.6%) with a mean age of 62.59±8.9 years were recruited (female, 54.70%). There was not any statistically significant difference between males and females regarding the prevalence of different refractive errors. With respect to different age groups, more prevalence of astigmatism (89.90%), myopia (46.60%), and anisometropia (35.1%) were found in patients ≥80 years old (P<0.001 for all). In addition,, the higher prevalence of hyperopia (56.60%) was observed in subjects with age in the range of 60-69 years old (P<0.001). Multiple multinomial logistic regression revealed a positive simultaneous effect of older age (OR= 3.14), as well as nuclear (OR=1.71) and posterior subcapsular (OR=1.61) cataracts on myopia prevalence, while those with higher level of education were at a lower risk of myopia (OR=0.28). In addition, subjects with higher body mass index (BMI) were found to be at a higher risk of hyperopia (OR=1.67). However, other factors including systemic and/or ocular diseases and outwork activities were not identified as risk factors.

Based on our findings, more prevalence of hyperopia was observed in subjects up to the age of 70 years while higher rates of myopia and astigmatism were noticed in older ages. Higher BMI was revealed as a risk factor for hyperopia, while older age and cataract were risk factors for myopia.