Drug-induced changes in pupillary size were recorded photographically in eight subjects with heterochromia iridis (HI) and in eight controls.
The patients with HI showed excessive mydriasis with 1% epinephrine, absent response to 4% cocaine, normal mydriasis with 1% atropine and miosis with 2.5% methacholine.
Both pupils responded in a similar fashion, suggesting a bilateral defect of sympathetic innervation of the iris.
Jammes JL, Nigam MP. Pupillary Autonomic Functions in Heterochromia Iridis. Arch Ophthalmol. 1973;89(4):291-292. doi:10.1001/archopht.1973.01000040293006