Abstract

Recent evidence suggests that glaucoma leads to early loss of large retinal ganglion cells^1,2 projecting to the Magnocellular layers of the dLGN: the so called "M" retinal ganglion cells. It is necessary for the present study, to appreciate that there are two subgroups of M-cells, the M_x-cells which are quite linear, and the nonlinearly responding M_y-cells, where the subscripts indicate physiological similarities with cat X and Y-cells³. In particular the retinal gain control described by Shapley and Victor⁴ for cat X and Y cells is strongly expressed in primate M- cells⁵. Except at very low temporal frequencies the quadratic response of Y-cells is larger than the linear response, especially at low spatial frequencies⁶, and the gain control effects Y-cells more, especially their quadratic response⁷. At least three studies indicate that M_y-cells are larger than M_x- cells^8,9,10. Therefore, methods for glaucoma diagnosis should perhaps appeal to M_y-cell physiology, e.g. the strong effects of gain control upon their nonlinear responses.

© 1995 Optical Society of America