Stereoacuity in unilateral visual impairment detected at preschool screening: outcomes from a randomized controlled trial.

PURPOSE Reduced stereoacuity is commonly found in association with reduced visual acuity or strabismus and may significantly affect neuro-developmental performance. Treatment for reduced visual acuity due to refractive error or amblyopia is believed to result in improved stereoacuity. This study was undertaken to investigate the effect on stereoacuity of treatment for unilateral visual impairment detected at preschool vision screenings, in the setting of a randomized controlled trial. METHODS Children identified through preschool vision screening were recruited and randomized to one of three groups (no treatment, glasses only, or full treatment with glasses and occlusion) for a period of 12 months, after which full treatment was given when indicated. Logarithm of the minimum angle of resolution (LogMAR) visual acuity and random-dot (Randot; Stereo Optical, Chicago, IL) stereoacuity were assessed at recruitment and at 12- and 18-month follow-ups by an orthoptist masked to group allocation. RESULTS One hundred seventy-seven children were recruited and randomized, 59 to each group. Comparison of stereoacuities showed an immediate median improvement of 30 seconds of arc in each group from refractive correction. Age significantly affected stereoacuity performance at recruitment (mean age, 4 years) but not at follow-up (mean age, 5 years). Deferring treatment did not affect final stereoacuity. CONCLUSIONS In this group, stereoacuity improved to a normal level as a result of refractive correction. Children in whom treatment was deferred for 12 months did not demonstrate significantly poorer stereoacuity than those in treatment.