A computerized red glass test for quantifying diplopia

BACKGROUND Accurate evaluation of diplopia during bedside physical examination is challenging. We developed a new computerized red glass test (CRT) to detect, localize, and quantify diplopia and investigated whether the CRT is useful and feasible. METHODS During the CRT, a white dot randomly appears on a monitor. Because a red glass is applied on the right eye, a patient can see one white dot and one red dot when diplopia is present. We defined the degree of diplopia as the direct distance of the two points with the largest deviation and compared the degree with the Hess score and Hess area ratio. RESULTS We prospectively enrolled 14 patients with binocular diplopia. Test-retest reliability of the CRT was excellent (overall intraclass correlation coefficient = 0.948, 95% CI 0.939-0.956). The degree of diplopia in the CRT was well correlated with both the Hess score (r = 0.719, p = 0.005) and the Hess area ratio (r = -0.620, p = 0.018). CONCLUSIONS The CRT can easily detect the presence of diplopia and provided the quantitative values of the degree of diplopia. The CRT was useful and feasible for improving routine bedside examination.