Prediction of early-onset esotropia from components of the infantile squint syndrome.

PURPOSE To examine the association between components of the infantile squint syndrome (ISS) and age of onset of esotropia among subjects in the Cooperative Amblyopia Classification Study (CACS). METHODS Fifty subjects were classified retrospectively as having early-onset esotropia (EOE) and 150 subjects were classified as having late-onset esotropia (EOE), depending on whether symptoms of (or treatment for) strabismus occurred before the first birthday or between the first and ninth birthdays, respectively. The authors compared the degree to which latent nystagmus (LN), dissociated vertical deviation (DVD), monocular asymmetry of optokinetic nystagmus (MOKN), monocular asymmetry of smooth pursuit (MSP), and perceived monocular speed bias (MSB) predicted EOE. RESULTS Slow-phase velocity of MOKN and MSP were faster in response to nasal than to temporal target motion. In contrast, MSB revealed that targets of equal velocity were perceived as moving faster temporally than nasally. The authors evaluated MOKN, MSP, and MSB as dichotomous and as continuous predictors. Dichotomous analysis showed significant associations between DVD and asymmetries of MOKN in the preferred eye of subjects with EOE. Univariate logistic regression models, based on DVD and LN as well as on continuous measures of MOKN, MSP, and MSB, revealed predictive power for all ISS components except LN. In the preferred eye, MSP asymmetry was the strongest single predictor of EOE; multivariate analysis revealed that prediction of EOE improved with the inclusion of DVD. CONCLUSIONS Multivariate analysis indicated that dichotomous measures of DVD and continuous measures of MSP were independent predictors of EOE in a population of 8- to 40-year-old subjects with strabismus. In the preferred eye, MOKN asymmetry was predictive of EOE in the absence of information about MSP. Predictive values of all ISS components depended heavily on the baseline prevalence of EOE in the target population.