Comparative Analysis of Strabismus Measurement Using a Video Oculagraphy System and Alternate Prism Cover Test

Abstract

Purpose: The aim of the study was to compare distance vision measurements obtained with video oculography (VOG) and an alternate prism cover test (APCT). Design: Single-center, retrospective, and cross-sectional. Methods: Eighty-seven subjects with strabismus were included. All patients underwent an optometric examination. The measurement of strabismus in distance vision was performed with the best optical correction using the APCT and the VOG GazeLab. Subjects were divided according to the type of strabismus; 41 were esotropic and 46 were exotropic. Results: The general comparison of APCT and VOG showed a mean difference of 0.60±2.74 prism diopters (Δ), not observing statistical differences between both methods (P=0.059) and presenting a correlation of 0.976 (P<0.001). Using APCT, the mean amount of esotropia for the group was 18.31±11.64 Δ and that of exotropia was 19.62±8.80 Δ. Compared with the VOG, the mean value of esotropia for the group was 18.65±11.65 Δ and that of exotropia was 19.48±8.62 Δ. The means are statistically different for the esotropia group (P=0.005) but not for the exotropia group (P=0.318). There was a high direct correlation between the methods of measurement for both the esotropic (R=0.980; P<0.001) and exotropic patients (R=0.975; P<0.001). Bland-Altman analysis shows a mean difference of 1.37±2.76 Δ for the esotropia patients and 0.31±2.66 Δ for the exotropic patients, respectively. Conclusions: This study demonstrated comparable results in measuring strabismus between VOG and APTC for esotropia and exotropia, with an excellent correlation between both methods and good agreement, especially in subjects with exotropia.