Strabismus: detection in a population-based sample and associated demographic factors

Purposes: To identify the frequency of occurrence of ocular deviation and the carriers characteristics in a population sample. Methods: Observational cross-sectional study, evolving a probabilistic sampling, between the years 2004 and 2005, including 11 cities of the Sao Paulo state. 10,994 individuals were examined. A sub-sample of this population identified as strabismus clinical diagnosis was the subject of the present study. The population was addressed by a trained team and standardized to the research procedures. The results were submitted to statistical tests through descriptive analysis, frequency of occurrence evaluation, contingency analysis and association tests (P<0.05). Results: Strabismus frequency of occurrence in the population studied was on average 1.4% (148 strabismus carriers), with no difference between gender. Depending on the type of strabismus detected, 46.3% presented ET, 38.2% cases of XT and 15.4% of deviations were associated with vertical or horizontal syndromes. Contingency analysis showed three ocular deviation carriers (2.3%) with blindness (both eyes affected) and seven (5.4%) had low vision in only one eye. According to the association of the ocular deviation and refractive error, ET and also XT can be present in individuals with varying degrees of myopia (up to -5.75 for XT and -2.50 for ET) or hyperopia (up to +9.00 for XT and +8.00 for ET). The association between strabismus and static spherical equivalent showed no significant difference between the types of eye deviation (P>0.05). Conclusion: The frequency of occurrence of strabismus in the population studied was 1,4%, with no difference between gender or ocular deviation type. The presence of blindness and low vision associated to ocular deviation reinforce the need for early treatment.