Spectrally selective flash early receptor potential (ERP) in dichromats.

The human spectrally selective flash early receptor potential (ERP) was studied in 12 dichromats: 6 protanopes (12 eyes) and 6 deuteranopes (12 eyes). Color filters used were Kodak Wratten filters No.23A, No.57, and No.47 for the red, green, and blue flash ERPs, respectively. The ERP amplitude was measured between the summits of R1 and R2. Mean amplitudes of the red flash ERP and green flash ERP were highly significantly decreased in the protanopes (p less than 0.001) and deuteranopes (p less than 0.01) as compared with the corresponding data in 10 normal subjects (20 eyes). The mean amplitude of the blue flash ERP was significantly lower than normal (p less than 0.001) in the deuteranopes. The mean ratio of the blue flash ERP amplitude to the red flash ERP amplitude showed a highly significant increase in the protanopes (p less than 0.001) and a highly significant decrease in the deutoranopes (p less than 0.001) compared with the mean ratio in the normal subjects, indicating a new, useful index for the objective clinical detection of congenital color defects.