To investigate the effect of contrast on scene perception
in people with age-related macular degeneration
(AMD) and to examine the relationship between task performance and macular function.
Nineteen patients with AMD and visual acuity below 20/50 were compared with 16 normally sighted, age-matched controls. Complete ophthalmologic examination (visual acuity, intraocular pressure measurement, and funduscopy) was performed in both patients and controls. In addition, Pelli-Robson contrast sensitivity
, fluorescein angiography, and visual field size were assessed in the AMD study patients. The stimuli were photographs of natural scenes containing or lacking an animal (the target). For each scene, the contrast of the original photograph was divided by 2, 4, and 8 to yield versions with a residual contrast of 50, 25, and 12.5%, respectively. The four levels of contrast were presented randomly and participants were asked to press a key when they saw an animal.
AMD patients exhibited a larger drop in target detection performance with the decrease in contrast than controls. We found a correlation between visual acuity and performance when the contrast was reduced to 50, 25, and 12.5% of the original value but not in the normal contrast condition. There were no correlations between letter contrast sensitivity
, visual field lesion size, and performance.
Our results suggest that optimal, stable contrast conditions would facilitate object recognition in everyday life for people with AMD.