Testing for glaucoma with the frequency-doubling illusion in the whole, macular and eccentric visual fields

Purpose: The frequency doubling (FD) illusion is the basis for new diagnost ic methods for glaucoma. The FD illusion is seen when low spatial frequency grating patterns are contrast modulated at high rates. The present experim ents examined which spatial frequencies might be optimal and whether high f licker rates are required. Methods: We determined contrast thresholds for the following: W1 a wide-fie ld 0.25 c/deg grating at 27 Hz contrast reversal; W2, as W1 but no flicker; MAC, 27 Hz, 4 c/deg grating presented to the central 4 degrees; and El to E7, seven spatial frequencies in the range 0.063-0.813 c/deg, 27 Hz, presen ted in a 5 degrees aperture at 15 degrees (nasal) eccentricity. Results: WI was the best predictor of glaucoma, Of the eccentrically presen ted stimuli. E6 (0.688 c/deg) was the best predictor of glaucoma while the lower spatial frequencies performed less well. Only MAC was significantly a ge-dependent.