Figure 4. ff-ERG responses were recorded using Burian-Allen bipolar corneal electrodes from all three affected individuals using a slightly modified procedure compared to the International Society for Clinical Electrophysiology of Vision (ISCEV) standard [10]. Cone single response (2.5 cd-s/m²) and 30 Hz flicker (2.5 cd-s/m²) were applied during background illumination (30 cd/m²). After 20 min (shorter for individual II-3), rod response was recorded using dim blue stimulus, and mixed rod-cone was elicited with a white (2.5 cd-s/m²) stimulus. The full field electroretinography (ff-ERG) responses of the affected individuals (II-1, II-3, II-4) indicate severe deterioration of cone function and rod function with residual mixed rod-cone responses (rows 1, 2, 3, respectively) in comparison to an individual with normal retina function (fourth row). The y-axis of each response indicates amplitude (μV), and the x-axis indicates time (ms) after the stimulus onset (time=0).