Fig. 37. Reduced first and second harmonic amplitudes in 12 eyes of seven patients with glaucoma (open squares) compared with 12 normal eyes of 11 normal subjects (solid squares). First harmonics originate in outer retinal layers and second harmonics originate in inner retinal layers. The stimulus was sine wave flicker of a 28-degree field with a 180-degree surround of equal mean retinal illuminance of 4000 trolands modulated at 75%. (Odom JV, Riemslag F, de Jong L, et al: Unpublished data collected at the Netherlands Ophthalmic Research Institute, Amsterdam, 1989.)