Evaluation of a New Clinical Test of Fusion Status: A Pilot Study

Abstract

Background Suppression is associated with binocular vision conditions such as amblyopia and strabismus. Commercial methods of testing fusion often only measure central fusion or suppression at near. The purpose of this pilot study was to assess a new iPad picture fusion test that assesses foveal and central fusion at near. Methods Participants aged 5 years and older presenting for eye examination at The Ohio State University College of Optometry were enrolled. Results from visual acuity, dry and wet refraction/retinoscopy, stereopsis and cover testing were recorded from the patient chart. The iPad picture fusion test, Worth four-dot, Worth type test with foveal letter targets, and Polarized four-dot were performed by one examiner in a randomized order at 40 cm. Testing was repeated with the anaglyphic filters reversed. Crosstabulation and McNemar chi-square analysis were used to compare the results between fusion testing devices. Results Of the fifty participants (mean age = 17.5), twelve reported suppression and one reported diplopia. Testability was excellent for all tests (98% to 100%). There were no significant differences between tests in reported results (P ≥ 0.22 for all comparisons). No difference in reported fusion or suppression status was observed with change in orientation of the anaglyphic filters. Six participants reported foveal suppression alone at near which was not identified with Worth four-dot at near. Conclusion The iPad picture fusion test provided excellent testability and agreement with commonly used tests of fusion and allowed testing of both central and foveal fusion at near. Nearly half (46%) of participants with suppression reported foveal suppression, supporting the importance of testing for foveal suppression.