Clinical Analysis of Strabismus in Twin

ABSTRACT

PURPOSE: To evaluate the genetic factor in development of comitant strabismus. METHODS: We retrospectively reviewed 48 patients of 24 twins classified into monozygotic or dizygotic twin and analyzed gestational period and birth weight, refraction, phenotype and age of onset, amount of deviation, surgical history, and associated systemic or other ocular anomaly except strabismus. RESULTS: Seventeen of the 24 twins (70.8%) showed phenotypic concordance. The concordance was significantly higher in monozygotic twins (15 of the 18 pairs, 83.3%) than in dizygotic twins (2 of the 6 pairs, 33.3%) (p=0.038). Out of 15 twins with monozygosity who showed concordance, the predominant phenotype was intermittent exotropia (9 pairs, 60.0%). Concordance rate according to phenotype was high in refractive or nonrefractive accommodative esotropia (3 of the 3 pairs, 100.0%) and intermittent exotropia (9 of the 10 pairs, 90.0%). Most of concordant pairs showed similarity in age of onset and amount of deviation between first and second child. CONCLUSIONS: The concordance rate in monozygotic twin was high, especially in refractive or nonrefractive accommodative esotropia and intermittent exotropia, and therefore genetic factor can be responsible for the development of these types of strabismus.