Visual object categorisation in people with glaucoma

PURPOSE: There is evidence that people with glaucoma exhibit difficulties with some complex visual tasks such as face recognition, motion perception and scene exploration. The purpose of this study was to determine whether glaucoma affects the ability to categorise briefly presented visual objects in central vision.

METHODS: Visual categorisation performance of 14 people with glaucoma (primary open angle glaucoma and preperimetric) and 15 age-matched controls was measured, assessing both accuracy and response times. Grey level photographs of objects (size) were presented for 28 ms foveally. Perimetric thresholds were normal for all participants within the central 3°. Two levels of contrasts were included: one medium level at 50% and one with high contrast at 100%.

RESULTS: On average, accuracy was significantly decreased by 7% (p=0.046) for the medium contrast stimuli in patients with glaucoma (87% of correct response, SD: 5%) compared with controls (94% of correct response, SD: 4.7%). Group average response times were significantly slower for the patients relative to the control group (712 ms, SD: 53 ms compared with 643 ms, SD: 34 ms for the control group; p<0.01). Performance was equivalent in the two groups when the picture contrast was 100%.

CONCLUSIONS: The impairment observed in the categorisation task supports previous work that demonstrates that people with glaucoma can have greater difficulties with complex visual tasks than is predicted by their visual field loss. The performance was equivalent to age-matched controls when contrast was maximised.