Abstract
Purpose :
Visual crowding is the impaired recognition of a target surrounded by flankers. Typically observed in peripheral vision, it also becomes elevated foveally in infantile idiopathic nystagmus (IIN). In peripheral vision, target-flanker similarity alters the strength of crowding, with a black target impaired more by surrounding black flankers than white. Flickering the elements (via periodic reversals in contrast polarity) has also been found to improve both acuity and crowding in peripheral vision. With the aim to reduce the elevations in crowding with IIN, we measured the effect of contrast polarity differences and flicker.
Methods :
We tested 6 IIN and 6 typical/control participants (aged 24-50), who identified the gap orientation of a target Landolt-C, presented to the fovea either in isolation or with 4 black (same polarity) or white (opposite polarity) flankers. QUEST was used to scale all elements to find the threshold gap size. Elements were either static or flickered with periodic contrast polarity reversals.
Results :
Crowding was present in the fovea of both control and IIN groups, with higher thresholds when flanked than unflanked. Crowding was particularly high for the IIN group. Unlike findings from peripheral vision however, we found no significant difference in thresholds when the flankers had the same vs. different polarity as the target, both for the controls (t5=-1.34 p=0.239) and the IIN (t5= -0.11 p=0.916) group. Similarly, the addition of flicker did not improve thresholds over the static condition in any of the unflanked or flanked conditions for the controls (e.g. with flankers of the same polarity: t5= -2.21 p=0.078), in fact making performance slightly worse in the IIN group (flanked-same: t5= -3.52 p=0.017).
Conclusions :
Our findings show that neither target-flanker differences in contrast polarity nor flickered reversals in polarity can reduce crowding in the fovea of both typical and IIN individuals. These results differ from the reductions in crowding found in peripheral vision, suggesting that the mechanisms that alleviate crowding are altered in both the typical and IIN fovea.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.