Feasibility assessment of novel binocular eye alignment monitor device for intermittent exotropia

Intermittent exotropia exhibits inherent variability in the percentage of time the eye deviates and the amount of exodeviation; therefore, assessing the magnitude and duration of the eye’s deviation is challenging. A portable monitoring device for longer assessments can enhance evaluation and management, providing an objective tool for assessing therapeutic rehabilitative interventions. The Binocular Eye Alignment Monitor (BEAM) was developed to objectively evaluate eye alignment over an extended period. Eye position was objectively recorded from 22 participants with binocularly normal vision and 15 with intermittent exotropia. Participants watched an age-appropriate movie of their choice on a television located 6 m away for 90 min after undergoing a strabismus evaluation in two sessions, each occurring on a different day. Test and retest sessions were analyzed for the percentage of test time deviated, as well as the maximum, mean, and median deviation magnitudes. Repeatability was assessed using the intraclass correlation coefficient and Bland-Altman plots. The BEAM has a temporal resolution of 8 milliseconds and a conservative spatial resolution of 2Δ. A Mann-Whitney U-test revealed significant differences between groups for the percentage of time deviated and the maximum, mean, and median deviation ( p < 0.01). Bland-Altman plots indicated good repeatability and narrow limits of agreement in the binocular normal vision group, whereas the intermittent exotropia group showed greater variability. Linear regression analysis showed a significant correlation between the maximum deviation measured by a clinician and the BEAM ( p < 0.03). These feasibility results warrant further evaluation of the BEAM for future randomized clinical trials.