Spectral characteristics of electroretinogram in X-linked dichromats--a preliminary study

Spectral characteristics of X-linked Dichromats (13 protanopes, 20 deuteranopes) were studied with spectral ERG. The results are as follows: The maximal spectral response of the b-wave in protanopes tended to shift toward the short wavelength side and the sensitivity to long wavelengths decreased obviously. The ratio value of the amplitude in 500 nm and in 620 nm (500/620) was greater in the protanope than that in the normal subject. Like the normals, the maximal response of the b-wave in deuteranopes appeared at 550-570 nm. Though the differences between the normals and deuteranopes in the ratio values (600/620 and b/a at 520 nm) were found by means of analysing a, b wave responses at each wavelength, most of the ratio values (600/620 or b/a at 520 nm) overlapped between the normals and deuteranopes. We established the discriminant function or score made up by the combination of two ratios basing on Fisher's rule, which can raise the diagnostic rate for deuteranopes.