Infant Visual Assessment: Using Eye Tracking to Measure Visual Acuity

Abstract

A technique commonly used to assess infants' visual acuity is forced-choice preferential looking, which relies on the propensity of infants to look at patterned stimuli over uniform grey. Existing tests use trained examiners to judge where an infant fixates; however, eye trackers offer the opportunity to measure eye movements quickly and automatically. In the present study infants' visual acuity was measured using a remote Tobii eye tracker (Tobii T120). Thirteen infants aged 4–8 months were seated before a screen and presented with a preferential looking task. On each trial a black and white chequerboard of variable spatial frequency was displayed on half of the screen, while uniform grey was displayed elsewhere. Eye tracking data were used to determine whether the infant fixated the chequerboard and to update the spatial frequency on subsequent trials according to a weighted up-down staircase targeting the 75% threshold. This initial study showed data in line with age norms are consistent across two testing sessions for some infants. Others yielded poor data or inconsistent performance. Future modifications will aim to make the test more engaging and to optimise its power and speed. These will provide a basis for a full assessment of the test's accuracy and reliability.