Paradoxic pupillary phenomena. A review of patients with pupillary constriction to darkness

The presence of pupillary constriction to darkness is said to be a useful indicator of retinal disease. However, it is also associated with optic nerve disease. The phenomenon has been reported in patients with congenital stationary nightblindness, congenital achromatopsia, bilateral optic neuritis, and dominant optic atrophy. We have observed this response in additional disorders, including anomalies of the optic nerve development, congenital nystagmus, and a variety of diseases affecting the retina. Notably, four of our patients with strabismus and amblyopia, but without apparent retinal or optic nerve disease, have also demonstrated this paradoxic pupil response. While the mechanism for pupillary constriction to darkness remains unclear, the finding of this response in patients without retinal or optic nerve abnormalities questions its value as a localizing sign.