L- and M-cone driven ERGs are differently altered in Best's macular dystrophy

To study the L- and M-cone pathways and their interactions in patients with Best's macular dystrophy (BMD), ERG response thresholds were measured to stimuli which modulated exclusively the L- or the M-cones, or both in various combinations. The ERG threshold data could be described with a vector addition model. Compared with normals, BMD patients showed generally larger amplitudes of the L-cone driven ERGs. However, the M-cone driven ERGs were similar in amplitude but significantly phase advanced. The data confirm our previous observations that L- and M-cone pathways can be affected differently by retinal degeneration, despite their large physiological and biochemical similarities.