شیوع انواع استرابیسم در بیماران ایرانی مبتلا به استرابیسمی The prevalence of strabismus types in strabismic Iranian patients

Introduction Strabismus is a very common ocular problem found at clinics of optometry and ophthalmology. In the USA, 3–5% of children are affected with 126,400 new cases occurring each year. The national prevalence of squint is 5.4% and this suggests that there are 7.02 million patients with strabismus in a population of 130 million.1 Strabismus constitutes a medical, social and psychological problem. Many studies investigating the prevalence of strabismus and its types have been conducted. The prevalence of convergent squint varies in different parts of the world; however, esotropia (ET) is the most common form of strabismus constituting from a half to two thirds of all misaligned eyes.2 In the US, ET was prevalent amongst 75% of total cases.3,4 In Ibadan, Nigeria, ET was found in 80% of total cases.5 Similarly in Ireland (UK), ET was found to be five times more common than exotropia (XT). However, the prevalence of strabismus differs between various races and the prevalence of different types of strabismus also varies according to race. An example of this is a study on preschool children in Ethiopia, where ET was found to be most the common type of strabismus.7 However, in Japanese children, XT was the most prevalent type of squint.8 According to the Baltimore Pediatric Eye Disease Study, manifest strabismus was found in 3.3% of white and 2.1% of African American children and ET and XT each accounted for close to half of all strabismus in both groups.9 Population-based data concerning the prevalence of strabismus or the relative prevalence of its types is not readily available for Iranians. This study presents the relative prevalence of various types of squint and also other pathologic findings that might be associated with it.