Y cells in the cat retina are more tolerant than X cells to brief elevation of IOP.

The responses of X and Y type retinal ganglion cells were extracellularly recorded from the cat optic chiasm or tract before and during brief intraocular pressure (IOP) elevation. The responses of both X and Y cells to stimulus flashes decreased monotonically with increase of IOP. Y cells had significantly higher tolerance to IOP than did X cells. This systematic difference was independent of the cell's retinal position. The findings support the conclusion that during brief IOP elevation pressure-induced ischemia is the main factor causing a decrease in ganglion cell responsiveness. Our findings also suggest a means of selectively eliminating the contribution of X cells to visual function. At moderate levels of IOP elevation X cells, but not Y cells, virtually cease to function.