STRABISMUS: FACTORS IN ANTICIPATING ITS OCCURRENCE *

Summary The genetic approach familiar to most clinicians is the Mendelian (or qualitative) approach, while quantitative genetics is still a generally unfamiliar one. However, quantitative genetics can be an extremely useful method for the study of continuously varying characteristics, including both human abnormalities and normal ranges of expression of individual differences This report is a summary of studies using quantitative genetics to determine if there is a relationship between genetic factors influencing ocular functions, as measured by clinical examination, and genetic factors influencing the occurrence of strabismus The purpose of this was to provide a means to predict the probability of the occurrence of strabismus in offspring of “nonaffected” parents. In this study, at least two measures appear to have some predictive value: reduced vergence ability and refractive errors In practical terms, this means that parents who collectively have both very low vergence ability and refractive errors, even though neither manifests strabismus, could be advised that any offspring are at risk for strabismus and therefore should be examined at a very early age The potential for early identification of individuals with unaffected parents who are at risk for certain abnormalities is sufficient to make application of quantitative genetics worthwhile in clinical medicine.