Figure 2. Electroretinograms from patient 1 (P1) and patient 2 (P2) compared to a normal subject. A: Photopic responses. No responses to red stimuli can be detected, whereas white stimuli show responses that are mostly within normal limits. Amplitudes of the response to blue stimuli are markedly higher than in normal subjects. Photopic 30-Hz flicker ERG responses are absent. Isolated rod b-wave amplitudes and maximal responses are generally within the normal limits (see B). B: Plots of scotopic response intensities from both patients. ERG intensities are shown as logarithmic values of stimulus intensity. P1 and P2 are represented in red and blue lines, respectively (one line for each eye). Black and Vertical lines represent the normal average and range from 100 normal eyes, respectively. As this parameter does not follow a normal (Gaussian) distribution but is skewed [15,16], to obtain the normal range the values were first converted to their log₁₀ values, which normalizes the distribution. Mean values±2.5 standard deviations (SD) were then calculated and the values were converted back to their antilog values. The a-wave amplitudes (left) are generally within the lower normal limit (except for P1 at the lowest ERG intensity, where it is lower than normal). The b-wave amplitudes (right) are within normal limits at all light intensities tested. C: Latency plots of the scotopic responses from both patients. For normal values, the normal range was calculated as the mean±2.5 SD. The a-wave latencies (left) are within normal limits (except for P1 at the lowest ERG intensity, where it is longer than normal). The b-wave latencies (right) are within the normal limits at all intensities, other than in P1 at 2.44 cd-s/m² (log=0.39).