COMPARISON OF RED-GREEN, BLUE-YELLOW AND ACHROMATIC LOSSES IN GLAUCOMA

Achromatic losses in glaucoma would be expected to be greater than, or equal to, red-green chromatic losses if the following assumptions are made: (1) the function of the remaining axons is either unchanged or non-selectively reduced; (2) red-green chromatic information is signal ed by the midget ganglion cell system; and (3) the function of the mag nocellular system is reduced at least as much as that of the midget ga nglion cells, This prediction was tested by measuring red-green (along with blue-yellow) mixture thresholds for 1 deg, 0.2 sec test spots pr esented on a color monitor on a white background of 50 cd/m(2), Ellips es were fitted to plots of green contrast as a function of red contras t (or yellow as a function of blue), and major and minor axes of these ellipses were taken as measures of chromatic and achromatic threshold s, respectively, The study population consisted of 29 eyes in 29 patie nts with early glaucoma; control data were derived from a data bank of 83 normal eyes, Red-green losses were significantly (P < 0.05) greate r than achromatic losses in 6 out of the 11 eyes which showed signific ant losses of either chromatic or achromatic sensitivity (or both), It is concluded that, for these eyes, at least one of the above three as sumptions is incorrect. (C) 1997 Elsevier Science Ltd.