Prevalence of primary monofixation syndrome in parents of children with congenital esotropia.

The prevalence of primary monofixation syndrome (MFS) in the general population is approximately 1%. This study was performed to determine the prevalence of primary monofixation in biological parents of children with congenital esotropia. Ninety children with congenital esotropia were seen between November 1991 and June 1992 by one ophthalmologist (M.M.P.). One hundred and twenty-nine biological parents of these children were screened for sensorimotor abnormalities. Twelve parents were found to have secondary MFS and were removed from the analysis. This left 78 apparently non-strabismic families consisting of a total of 117 parents. Seven parents were identified as having primary MFS. The prevalence of primary MFS in this population is 9% of families and 6% of parents. Congenital esotropia is believed to be inherited in a multifactorial fashion. We believe that this increase in the prevalence of primary MFS compared to the general population lends support to the hypothesis that primary MFS may be a mild (subthreshold) effect of the "gene(s)" that cause congenital esotropia.