Abstract
Purpose:
Previous studies suggest that the prevalence of strabismus subtypes is related to ethnicity, with exotropia being more frequent in Asian populations and esotropia in Caucasian populations. This predilection may be determined by refractive error. We investigated the relationship between strabismus subtype and refractive error in a large population-based cohort of young children.
Methods:
The Generation R Study is a multi-ethnic population-based birth-cohort study in Rotterdam, the Netherlands, which includes 6690 children. LogMAR visual acuity (LEA charts) was determined at age 6, and those with LogMAR acuity > 0.1 or those receiving ophthalmic care were evaluated for ocular alignment and cycloplegic refraction. Strabismus subtype was determined by the treating orthoptist according to a national classification system.
Results:
Mean age of children was 6.2 (SD ±0.5) years. , N=110 (1.6%)children were identified with a manifest strabismus. Of these convergent strabismus was most common (n = 74, 1.1%), with accommodative esotropia (n = 55, 0.82%) as nost common subtype, followed by constant esotropia (n = 15, 0.2%) and infantile esotropia (n = 4, 0.06%). Exotropia was detected in n=25 (0.4%) children; n=10 (0.1%) children had special forms of strabismus such as congenital trochlear palsy, Duane, congenital fibrosis and acquired palsy. Mean spherical equivalent was +4.67D (SD ±1.94) in accommodative esotropia and +0.04D (SD 2.17; P<0.01) in exotropia.
Conclusions:
Type of strabismus appears to be associated to refractive error; exotropic children are more myopic, whereas esotropic children are more hyperopic. The increasing prevalence of myopia worldwide may determine the relative increase of exotropia and may be the cause of the ethnic variation in strabismus subtypes.