Following from the finding that the spectral pattern ERG responds to both luminance and color, a test was devised that pits one against the other in such a way that a numeric score is derived which reflects the amount of color response required to cancel the luminance response. Contrary to expectations derived from the psychophysical literature on glaucoma, it was found that with the progress of glaucoma less and less color response is required to cancel luminance response indicating that the luminance ganglion cells deteriorate earliest. Tests on populations of normals, glaucoma suspects and confirmed glaucoma patients who do not yet show consistent visual field defects on the Humphrey Test, reveal significantly lower scores on this test for those with confirmed glaucoma than for the suspects and for both suspects and confirmed glaucomas than for the normals. There was no significant difference between test and retest, showing high reliability. It was also shown by tests on paralyzed and narcotized rhesus monkeys that earliest differences between normal control eye and eye with induced high intraocular pressure are detected outside the central 17 degx10 deg in the retinal periphery with a 34 deg.x20 deg. checkerboard pattern. This was underscored by finding the largest difference between the response of treated and control eye with the larger pattern plus occlusion of the central 10 degrees. Finally, it was shown on two normal humans that larger pattern ERG response occurred to the larger of the two fields and were clearly discernable when the central 10 degrees were occluded. Therefore, it is concluded that a form of spectral pattern ERG visual field test is shown feasible in which recording responses to annular checkerboard patterns of different inner and outer diameters is contemplated. A test device for following the progress of glaucoma and the success of treatment at a time earlier in the course of the disease than can be revealed by the subjective visual field tests was also designed.
Spectral pattern ERG for detection of glaucoma