Contraction anisocoria: nasal versus temporal illumination.

The size of the pupillary reflex responses to flashes of light from 2 sources, positioned on each side of the visual axis, was measured in both eyes of 20 healthy subjects. When the nasal retina of one eye was illuminated, the direct reaction of that eye exceeded the consensual reaction of the other eye by a mean of 6.1% of reflex amplitude, whereas illumination of the temporal retina gave equal reflex responses.