Fig. 6. Computer-averaged full-field electroretinograms from a 26-year-old man with X-linked retinitis pigmentosa obtained in response to 10-μsec flashes of white light at 16,000 foot Lamberts presented at 0.5 Hz (n = 64), 30 Hz (n = 256), and 42 Hz (n = 256) at base line (Year 0) and at 2-year follow-up (Year 2). Three consecutive response averages are superimposed in each case. Vertical broken lines denote flash onset for 0.5-Hz condition and onset of one of train of flashes for 30-Hz and 42-Hz conditions. (Berson EL, Sandberg MA, Rosner B et al. Natural course of retinitis pigmentosa over a three-year interval. Am J Ophthalmol 1985;99:240.)