Abstract:
Primary Objective: To investigate and evaluate any difference in the level of visual crowding experienced by individuals with severe to profound hearing loss compared to individuals with ‘normal’ hearing. Methods: Participants underwent an audiological test to ensure valid candidacy for the test (severe to profound hearing loss) or control (‘normal’ hearing) group. Visual threshold acuity was measured for recognition of SLOAN optotypes in each of the four conditions; central uncrowded, central crowded, peripheral uncrowded and peripheral crowded. Threshold size was used to calculate crowding and eccentricity ratios to measure the effects of crowding and eccentricity. Visual fixation was measured throughout the threshold acuity task. Basic selective visual attention was measured using the pure and discriminate reaction time tasks of the CAB®. Results: Weighted independent sample t-tests revealed individuals with severe to profound hearing loss experience significantly less peripheral crowding, and a strong peripheral advantage when compared to those with normal hearing. The findings also indicated that the test group had significantly poorer maintenance of central visual fixation throughout the crowding task. There was no significant difference in visual reactivity, however those with normal hearing were more accurate in their responses. Conclusions: Individuals with severe to profound hearing loss experience relief of peripheral crowding and a strong peripheral advantage, suggesting long term auditory deprivation results in an increase in peripheral resources. These findings provide support for the compensatory model of sensory deprivation.
