Chromatic and achromatic defects in patients with progressing glaucoma

To evaluate the pattern of losses associated with glaucomatous injury in pa tients with progressing glaucoma, functional losses were examined in 14 pat ients with progressing glaucoma using tests for which detection should be s electively mediated by one of three psychophysical mechanisms. Red-on-white increments, blue-on-white increments and critical flicker frequency were u sed to isolate the responses of the red-green chromatic mechanism, the blue -on chromatic mechanism, and the high-frequency flicker achromatic mechanis m. For our 3.1 degrees circular stimuli, chromatic defects were found in a greater number of the patients with glaucoma than were achromatic defects. We evaluated these defects in terms of two existing hypotheses: preferentia l loss and reduced redundancy. The greater sensitivity to glaucomatous inju ry of chromatic tests. compared to achromatic tests, found in this and othe r studies and the apparent discrepancy between anatomical and psychophysica l studies can be parsimoniously explained by differences in cortical summat ion of ganglion cell responses for the chromatic and achromatic pathways. ( C) 2001 Elsevier Science Ltd. All rights reserved.