Comparison of refractive errors and factors associated with spectacle use in a rural and urban South Indian population

PURPOSE: To compare the prevalence of refractive errors and factors associated with spectacle use in a rural and urban south Indian population. MATERIALS AND METHODS: Four thousand eight hundred subjects (age >39 years) each from rural and urban Tamil Nadu were enumerated for a population-based study. All participants underwent a complete ophthalmic evaluation including best-corrected visual acuity (BCVA), objective and subjective refraction. Out of 3924 rural responders 63.91% and out of 3850 urban responders 81.64% were phakic in the right eye with BCVA of 20/40 or better and were included in the study. Association of spectacle use and refractive errors with different parameters were analysed using logistic regression. STATISTICAL ANALYSIS: Chi square, t test, Chi square for trend and Pearson′s correlation coefficient were used for analysis. RESULTS: Spectacle use was significantly higher and positively associated with literacy and employment in the urban population. The age and gender-adjusted prevalence of emmetropia, myopia of spherical equivalent (SE) ≤-0.50 diopter sphere (DS), high myopia (SE ≤-5.00DS), hyperopia (SE >0.50DS) and astigmatism ≤ 0.50 diopter cylinder (DC) were 46.8%, 31.0%, 4.3%, 17.9% and 60.4% respectively in the rural population and 29.0%, 17.6%, 1.5%, 51.9%, 59.1% respectively in the urban population. The prevalence of emmetropia decreased with age (p < 0.001); prevalence of myopia and high myopia increased with age (p = 0.001) and were associated with nuclear sclerosis (p = 0.001) in both populations. Hyperopia was commoner among women than men (p = 0.001); was positively associated with diabetes mellitus (p = 0.008) in the rural population and negatively with nuclear sclerosis (p = 0.001) in both populations. CONCLUSION: Spectacle use was found to be significantly lower in the rural population. The pattern of refractive errors was significantly different between both populations.