Contrast sensitivity (CS) and differential light sensitivity (LUE) tend to deteriorate with increasing severity of the neuropathy. However, the correlation between the two psychophysical functions is low for the total number of optic neuropathies as well as for groups with different visual acuities. This fact is mainly explained by the range of scatter in LUE values. Moreover, visual acuity is much better correlated with CS than with LUE. CS and LUE represent different visual functions that may be processed by separate neural structures.