Visual impairment and myopia in Brazilian children: a population-based study

To determine the frequency of myopia and other causes of visual impairment (VI) in individuals aged 10 to 15 years who live in a typical Brazilian city.

Random selection of geographically based clusters was performed to obtain a sample of children aged 10 to 15 years in Gurupi City, Tocantins, Brazil. From June to August 2007, children in 12 clusters were enumerated through a door-to-door survey. All children with an uncorrected visual acuity (VA) worse than 20/32 in either eye were scheduled for ophthalmologic evaluation, including VA and ocular motility testing, cycloplegic refraction, and external, biomicroscopic, and dilated funduscopic examinations. The primary cause of VI was determined for eyes with an uncorrected VA of 20/40 or worse.

A total of 1590 children were examined; 814 (51%) were boys and 776 (49%) were girls. The prevalence of uncorrected, presenting and best-corrected VA of 20/40 or worse in the better eye was 5.72%, 2.83%, and 0.81%, respectively. The primary cause of VI in one or both eyes was refractive error in 65 (89%) of 73 children, amblyopia in 4 (5.5%) of 73 children, retinal disorders in 3 (4.1%) of 73 children, and congenital cataracts in 1 (1.4%) of 73 children. In this population, the prevalence of VI-related myopia was 3.14%.

The prevalence of VI among children aged 10 to 15 years in this typical Brazilian city is low and similar to other school-based studies, and most of the VI is caused by uncorrected myopia.