18th annual Frank Costenbader Lecture. Fusion and suppression: development and loss.

A retrospective study (coauthored with Geraldine Tillson) of 118 patients with the congenital esotropia syndrome is described. All patients were aligned with surgery and, in some cases, glasses as well, within 10 prism diopters of orthotropia before the age of 2 years and had remained so aligned for at least a year. A standardized final examination was performed on patients over the age of 6 years, after at least 5 years' follow up, to study the effect of significant refractive error, amblyopia, nystagmus, dissociated vertical divergence, and inferior oblique overaction on the sensory outcome. None of the patients obtained central fusion. Fifty-three of 118 obtained peripheral fusion with at least 5 delta of fusional amplitude. Twenty-eight of the 53 fusers had stereopsis. The findings did not show any factors to explain why 65 did not obtain fusion. A congenital lack of the potential to develop fusion is postulated. The development of fusion and suppression is discussed with relevant references. Evidence is presented that the anatomical location of the lesion in central fusion disruption is in the midbrain. Fusion may be lost, in visual adults, without developing suppression from prolonged sensory deprivation. Examples include unilateral cataract, uncorrected unilateral aphakia, and unilateral severe herpetic keratitis.