Abstract
Purpose :
The contrast sensitivity function (CSF) is a highly valuable measure of visual health, but has generally been difficult or impossible to assess in individuals with cognitive impairment. We show that a rapid gaze-based task can assess contrast sensitivity in children with a range of neurological disorders such as cortical visual impairment (CVI), including non-verbal children.
Methods :
We measured CSFs in fifteen child in-patients (age 4 to 18) with varying levels of neurological deficit using the eye-tracking-based task Gradiate. This task displays drifting band-filtered noise targets and determines when the participant is smoothly tracking a target with their eyes, then advances the target’s spatial frequency and contrast in real time until it is no longer visible. Five distinct thresholds were measured multiple times over multiple sessions in order to form a CSF. We also measured six-threshold CSFs in the most impaired children with a variant of Gradiate that uses scrolling full-screen noise. In this variant, the tester can manually toggle an attractive cartoon overlay to recapture the participant's attention (a “bait-and-switch”).
Results :
Well-formed CSFs were obtained from ten out of fifteen children, though different patients required different numbers of testing sessions to overcome their varying cognitive and attentional deficits. The low rate of false positives in the Gradiate task allows us to infer thresholds from the best results across multiple sessions with high confidence. Figures 1 and 2 depict example CSFs from children with severe (non-verbal) and mild traumatic brain injury, respectively. Five children exhibited no tracking behavior in any session and could not be assessed.
Conclusions :
Our findings indicate that a non-verbal, gaze-based tracking task makes it possible to measure contrast sensitivity in young and/or impaired participants. Due to the task’s inherent low false positive rate, transiently poor performance that is due to cognitive rather than visual impairment is readily detectable. Quantitative contrast sensitivity measurements in these clinical populations would aid in diagnosing specific visual disorders in greater detail than broad-spectrum categories such as CVI. These assessments may also be developed further into potential behavioral therapies, which we are currently exploring.
This is a 2021 ARVO Annual Meeting abstract.