HIDDEN VISUAL-LOSS IN OPTIC NEUROPATHY IS REVEALED USING GABOR PATCH CONTRAST PERIMETRY

Visual sensitivity was evaluated in the central 16 degrees of the visu al field in normal subjects, in patients with glaucomatous optic neuro pathy, in glaucoma suspects, and in eyes of patients with multiple scl erosis without evidence of active optic neuritis. A novel method was u sed to assess sensitivity called contrast perimetry (CP). CP essential ly samples every point in the central 16 degrees field, and the normal and deviant responses are relatable to spatial summation of contrast signals. in each visual field quadrant 1 cycles/degree sinusoidal grat ing stimuli limited in area by a gaussian circular aperture (called a Gabor stimulus) were presented. Contrast sensitivity was measured as a function of stimulus size. The normal curve is nearly S-shaped: For s mall Gabors contrast sensitivity increases slowly, then accelerates an d then flattens again. Patients' results fell into two broad categorie s: a loss more or only evident for small Gabors and another type of lo ss for both small and large Gabor size. Glaucoma suspect and most glau coma eyes showed predominant losses to small Gabors. There were more e yes and more VF quadrants identified by contrast perimetry as abnormal compared to the diagnostic yield of the Humphrey 30-2(central) visual field even though a Humphrey VF defect was defined liberally. Apparen tly, contrast perimetry may yield diagnostically useful information of paracentral visual sensitivity. Furthermore, the results suggest that selective losses in POAG and some glaucoma suspects occur to spatiall y broad-band retinal mechanisms, presumably ganglion cells. (C) 1997 W iley-Liss, Inc.