Reaction times to edges of variable sharpness in age-related maculopathy

An experiment was conducted to measure reaction times to edges of varying sharpness profiles presented on an oscilloscope in aged normals, subjects with age-related maculopathy (ARM), and subjects who had 6/6 acuity with drusen and/or pigmentary changes visible ophthalmoscopically, i.e., subjects at risk of developing ARM. Mean reaction time increased with decreased sharpness of the edge profiles for all groups tested. In subjects with ARM there was a further increase in mean reaction time of up to 20% for all edge profiles. In the group at risk of developing ARM there was a small but significant increase in mean reaction time for all edge profiles. It appears that there are measurable functional deficits in subjects whose acuity is normal but who show signs of developing ARM. This performance decrement may be important in the recognition of signs and signals in the driving environment, inasmuch as edge sharpness has been identified as an important component of sign conspicuity.