Objective Assessment of Intermittent Exotropia Magnitude and Control Using the Binocular Eye Alignment Monitor

To compare an objective assessment of intermittent exotropia (IXT) control and deviation size using the binocular eye alignment monitor (BEAM) to standard clinical assessments.

IXT control and deviation size were evaluated in 15 participants aged 8-35 years. Participants completed two visits that included a 90-min BEAM eye movement recording at a distance (6 m) to evaluate distance IXT size and control of the deviation objectively. IXT control was assessed using the mean of three measurements of the IXT Office Control Scale, and the deviation size was measured with the prism alternate cover test (PACT).

The mean IXT control score in the IXT participants was 2.2 ± 1 points, which was weakly correlated with the percentage of time strabismic as measured by the BEAM (Spearman's correlation coefficient = 0.29; p = 0.30). Distance PACT and mean BEAM deviation size demonstrated a moderate, non-significant association (ρ = 0.47, p = 0.08). BEAM measurements were consistently smaller than PACT measurements. IXT distance control (0.44; 95% CI: 0.04-0.80; p = 0.03) and the median deviation size measured by the BEAM (z = -2.1, p = 0.03) were significantly different between visits 1 and 2 (z = -2.1, p = 0.03); however, the percentage of time deviated (BEAM) was not significantly different between the two study visits (z = -0.63; p = 0.50).

The notable differences in control observed with the BEAM compared to current clinical measures suggest that office control scores and prolonged objective monitoring may capture different aspects of IXT control. Objective monitoring over extended periods may be a valuable complement to traditional clinical assessment in both research and clinical care.