Genetic analysis of vergence measures in populations with varying incidences of strabismus.

Genetic parameters were contrasted for vergence amplitudes within three populations--esotropic, exotropic, and randomly selected populations-who differed in their incidence of subtypes of strabismus. In general, heritabilities for convergence exceeded those for divergence, and heritabilities for recovery points exceeded those for break points. Heritability estimates for diveregence amplitudes were significantly different for the random and esotropia populations, while convergence heritability estimates for these groups were similar. Thus, gene differences influencing divergence ability contributed to genetic variance for strabismus.