Clinical Management of Monofixation Syndrome due to Microtropia

BACKGROUND: Monofixation syndrome is a binocular vision disorder characterized by peripheral fusion with a central suppression of one eye due to smallangle strabismus (microtropia) or anisometropic amblyopia. Reduced stereopsis and acuity are noted in the non-fixating eye. Although often left untreated due to good cosmetic appearance, central suppression and reduced stereopsis can affect visual performance, comfort, and depth perception. CASE REPORT: EJ, a 17-year-old Caucasian female was previously treated for amblyopia of the left eye (OS) with glasses and patching since age 8 with no improvement to vision. EJ experienced the following symptoms: blurred vision at near when reading, blurred vision at far distances, eye pain and fatigue, difficulty copying from the board, difficulty seeing at night while driving, and poor depth perception. Entering uncorrected visual acuity was 20/20-2 OD and 20/50-2 OS with Snellen Letter Chart. Near uncorrected acuity was 20/20 OD and 20/200 OS with a reduced Snellen chart at 40 cm. Microtropia of 2 to 12 prism diopters of esotropia, eccentric fixation on visuoscopy, and central suppression on various tests were measured. EJ was diagnosed with monofixation syndrome, monocular esotropia of the left eye, strabismic amblyopia of the left eye, suppression of binocular vision (OS), and fusion with defective stereopsis. The patient completed 19 sessions of in-office vision therapy with the practice of home reinforcement activities between therapy sessions. Visual performance was reassessed after 10 and 19 sessions of vision training with improvements noted in acuity, accommodation, oculomotor accuracy and speed, eye alignment, fusional vergence skills, and stereopsis. CONCLUSION: Optometric vision therapy can decrease suppression, improve central fusional ability, visual acuity, accommodative accuracy, and stereopsis in a patient with monofixation syndrome.