Binocular summation in comitant exotropia: Change after surgery

Purpose: To assess the change in binocular summation (BiS) in comitant exotropia (XT) after strabismus surgery. Methods: This is a prospective study on 20 patients who underwent surgery for comitant XT over a one year period. Patients with sensory exotropia and nystagmus were excluded. Best-corrected visual acuity (VA) and contrast sensitivity (CS) of both eyes separately and together (binocularly) were recorded. BiS score was calculated as binocular score minus better eye score. BiS score at the end of 3 months was compared with the preoperative data. Results: The mean +/- SD of BiS score increased from 2.95 +/- 0.88 to 4.55 +/- 0.68 (P-value < 0.0001) for VA (on ETDRS letters) and from 2.75 +/- 0.44 to 4.5 +/- 0.76 (P-value < 0.001 for CS (on Pelli-Robson chart) after surgery. Conclusion: There is significant improvement in BiS in XT after strabismus surgery. Authors recommend its indusion in evaluation of functional outcome of XT surgery.