Overminus Lens Therapy for Intermittent Exotropia

Abstract

Treatment of intermittent exotropia includes orthoptic therapy, prisms, surgery, the use of minus lenses, or simply observation. We have made increasing use of overminus lenses for this problem in our practice obtaining good results in a number of cases. A retrospective study was undertaken to further determine the extent of success as defined by improved control of the tropia or conversion to a phoria.

A review was made of 100 patients treated with minus lenses between April, 1988 and January, 1993. Those with insufficient follow-up or non-compliance with glasses were eliminated. Data on 74 cases was analyzed with divisions into primary, residual, or consecutive deviations. Patients were divided into three groups according to deviation size: Group I with more than 25^A; Group II 20–25^Δ; and Group III less than 20^Δ. The overall success rate with minus therapy was 61%. Success rate increased as the pretreatment angle size diminished with those in Group II and III being more successful. Additionally those with a primary or residual deviation fare better than consecutive intermittent exotropia. Twelve patients, 16.6%, are out of glasses or have eliminated overminus with continued success.

• intermittent exotropia
• overminus lenses
• accommodative convergence
• angle size
• angle character