The effects of increased visual task demand on foveation in congenital nystagmus

Commonly, when an individual with congenital nystagmus (CN) performs a visually demanding task their nystagmus intensifies and their visual acuity decreases, probably due to poorer foveation. However, the relationship between fixation attempt and nystagmus waveform has never been quantified. In this study 14 CN subjects viewed a Landolt C of varying orientation and size. They indicated its orientation via a button array whilst eye movements were recorded. Foveation was uncorrelated with optotype size. These results suggest that CN is not exacerbated by visual demand per se rather the need to do something visually demanding of importance to the individual.