Using the White Disk Test to Predict Fusional Potential.

INTRODUCTION: Fusional potential in patients experiencing binocular torsional diplopia may be challenging for the clinician to assess, particularly when accompanied by vertical and horizontal diplopia. OBJECTIVE: To demonstrate a clinical test that may help predict if binocular fusion can be achieved once cyclotorsion is alleviated. DESIGN: Video recording demonstrating how to perform the white disk test and retrospective chart review of patients tested with the white disk test. RESULTS: Twelve patients with binocular torsional diplopia were included. All subjects had excyclotorsion, 11 (91.7%) had combined vertical and horizontal strabismus and 1 patient (8.3%) had vertical strabismus. Eleven patients (91.7%) were able to achieve single binocular vision with the white disk test and 1 patient (8.3%) demonstrated brittle fusion. The white disk test successfully predicted postoperative fusion in 10 of 11 patients (90.9%). Eight patients (66.7%) demonstrated improved stereopsis after surgery. CONCLUSION: The white disk test was found to be very useful in predicting fusional potential in patients that experience binocular torsional diplopia.