Role of Prism Adaptation in Intermittent Exotropia: Evaluating Control and Binocular Function

Abstract

Background: Intermittent exotropia is a childhood binocular vision disorder characterized by fluctuating outward ocular deviation, reduced fusional stability, impaired control, and possible deterioration of stereoacuity. Prism adaptation may reduce fusional demand and support binocular alignment, but its short-term clinical effect on combined motor, functional, and sensory outcomes requires clearer evaluation. Objective: To assess changes in ocular deviation, control scores, and stereoacuity after six weeks of prism adaptation therapy among school-aged patients with intermittent exotropia. Methods: This quasi-experimental pre-test/post-test study was conducted at Mayo Hospital, Lahore, among children and adolescents with basic-type or divergence-excess intermittent exotropia. Of 59 initially recruited participants, 30 completed prism adaptation therapy and follow-up assessment. Participants received individualized Fresnel press-on or ground-in prisms according to measured deviation and were assessed at baseline and after six weeks. Outcomes included distance and near deviation, distance and near control scores, and stereoacuity. Results: Mean distance deviation decreased from 25.60 ± 6.80 PD to 14.20 ± 4.50 PD, while near deviation decreased from 22.40 ± 5.50 PD to 12.50 ± 3.80 PD. Distance control score decreased from 3.20 ± 1.15 to 1.40 ± 0.85, near control score decreased from 2.80 ± 1.05 to 1.10 ± 0.75, and stereoacuity improved from 215.50 ± 110.20 to 85.50 ± 45.20 seconds of arc. Conclusion: Prism adaptation was associated with short-term improvement in motor alignment, functional control, and stereoacuity among completers; however, controlled studies with longer follow-up are needed to confirm its comparative effectiveness.