Long-term stability of alignment in the monofixation syndrome

From a collection of 328 patients with congenital esotropia, 80 patients were identified who had a minimum 4-year follow-up after surgical alignment within 8 prism diopters (pd) of orthophoria. These patients were subdivided into two groups: the M.S. group (38 patients) demonstrated the monofixation syndrome; the NO M.S. group (42 patients) did not have monofixation. The alignment of patients in each group was followed over time. After 17.5 years, 74% of patients in the M.S. group maintained alignment within 8 pd of orthophoria. In the NO M.S. group, only 45% were well aligned after 14 years. The mean time to loss of stability was significantly shorter for the NO M.S. group (P less than 0.005). Our findings suggest achievement of the monofixation syndrome improves but does not guarantee stability of ocular alignment.