Disconjugacy Of Eye Alignment Is Greater With Near Fixation During Binocular Viewing In Amblyopia

Binocular eye movements were recorded at 500 Hz using the EyeLink 1000 eye tracker (SR Research Ltd., Ontario, Canada). Twenty subjects (nine normal and eleven amblyopic; age: 8-45 years) were asked to fixate on a blue cross subtending 0.5° at a near distance of 57 cm or at a far distance of 4 m for 20-second epochs of binocular or monocular viewing. Disconjugacy of eye alignment was estimated by the area of the 68% bivariate contour ellipse (BCEA) for the difference between right and left eye positions, by the percentage of fixation time within a 0.1°x 0.1° range, and microsaccade characteristics. Mean ± standard error of the mean were shown, log(BCEA) was used to normalize the distribution, and significance testing was performed with the Student's t-test.