A PUPILLOMETRIC CORRELATE OF SCOTOPIC VISUAL-ACUITY

While not easily fit into the classic descriptions of the pupillary li ght reflex, previous studies reported that changes in the spatial comp osition of the retinal image can evoke a pupillary response. The prese nt study extends this observation by showing that the pupil constricts in response to scotopic as well as photopic spatial patterns. Moreove r, the amplitude of the scotopic response decreases with increasing sp atial frequencies suggesting a pupillary spatial acuity of about 3 c/d eg. The scotopic pupil acuity is similar to the scotopic perceptual vi sual acuity measured in the same observers.