Prevalence of Strabismus and its type in Pediatric age group 6-15 years in a tertiary eye care hospital, Karachi

Strabismus, also called squint, tropia and heterotropia, is a common ocular disorder having 1% to 4% of prevalence.1 There are two types of strabismus: concomitant and incomitant. Concomitant strabismus is a condition in which the ocular angle of deviation remains constant in each direction of gaze. It includes the most common types of strabismus, including exotropia, esotropia, hypetropia, monofixation syndrome and microstrabismus. In the incomitant strabismus, which is also called as complex or paralytic strabismus, the misalignment of eyes or the angle of deviation differs with each direction of gaze. According to different surveys the global prevalence of strabismus shows the estimated prevalence of squint in the general population is from 2 to 5%. Between 5 and 15 million individuals in the United States may have this condition, several studies of clinical populations have reported that esotropia appears to occur approximately 3 times as often as exotropia in children.2 However, the National Health Survey of individual’s 4−74 years of age found a higher prevalence of exotropia (2.1%) than esotropia (1.2%) in the U.S population. This difference is probably related to the fact that the overall prevalence of strabismus in persons 55−75 years of age (in whom exotropia is more common) is 6.1% substantially greater than for very young children 1−3 years of age (1.9%) or children and adults 4−54 years of age (3.3%).3 The prevalence of exotropia may be underestimated, because it is most often an intermittent strabismus. For Hispanic/Latino and African American children ages 6−72 months in Los Angeles, California. The prevalence of strabismus was 2.4% for the former and 2.5% for the latter group. Exotropia was more common than esotropia.4 Approximately 50% of all childhood esotropia are either fully or partially accommodative. An esotropia is partially accommodative when the accommodative factors of uncorrected hyperopia and/or a high accommodative convergence/accommodation (AC/A) ratio contribute to, but do not account for. The entire strabismus, non-accommodative esotropia is the second most common form of childhood esotropia, accounting for approximately 10% of all strabismus. Infantile esotropia accounts for approximately 8.1% of cases of esotropia, affecting 1 in every 100−500 persons.5 Intermittent exotropia is the most common type of exotropia, affecting nearly 1% of the population. Exotropia has been reported to be more prevalent among Asian and African American populations than among Caucasians women comprise 60 -70% of patients with exotropia.6 The prevalence of strabismus in Nigeria was 0.14%.7 In Pakistan, children under the age of 15 years account for 45% of the total population. The overall estimated prevalence of strabismus in Pakistan is 5.4%. Out of this 2.5% strabismus patients are under the age of the 5 years while 2.9% patients are over the age of 5 years. The national prevalence of squint 5.4% suggests that there are 7.02 million patients with strabismus in a population of 130 million.8 The prevalence of strabismus conducted in Lady Reading Hospital, Peshawar, and The frequency of comitant convergent squint found in this study is 2.5% is almost similar to the Prevalence of squint in Pakistan which is 2.75%.9 In the population of Rawalpindi, the frequency of all vertical deviations was 11.4%. Pure vertical deviation