Interocular sensitization to a rod-detected test.

Intense red light adaptation of one eye lowers the dark adapted ("absolute") threshold of a 661 nm, extrafoveal, 1.02 deg test flash in the other eye, by about 0.15 log units, for 10-15 min. This effect ("interocular sensitization") also occurs with an extrafoveal 491 nm test, but does not occur if the 661 nm test is foveal, or is made small and brief. Blue or green light adaptations, matched either photopically or scotopically to the red, do not produce interocular sensitization. Thus the conditions producing the effect include intense red light adaptation of one eye, and scotopically mediated detection in the other.