Electroretinogram responses from patient IV-4 with photopic single flash and 30 Hz flicker response stimuli.

Both panels show responses at younger age 38 years on top and at 55 years on bottom. The single flash cone responses at age 38 was reduced approximately 80% from normal and was no longer detectable 17 years later (Panel A). The cone flicker response was similarly reduced at age 38 and further diminished by age 55 (Panel B).