A new cause for difficulty in seeing at night.

A syndrome is described in which patients complain of inability to see at night, although their rod and cone thresholds are normal. In such persons the rods, when dark-adapted, elevate cone flicker thresholds by 2 log units or more, and this condition is the basis of their complaint. Patients are often thought to be hysterics or to have congenital stationary night blindness.