Flynn phenomenon is paradoxical constriction of the pupils in darkness. This has been documented in various conditions including congenital achromatopsia, following optic neuritis, and in autosomal dominant optic atrophy.
Frank JW, Kushner BJ, France TD. Paradoxical pupillary phenomena: a review of patients with pupillary constriction to darkness. Archives ofOphthalmology 1988; 106: 1564-1566