A prospective evaluation of cholinergic supersensitivity of the iris sphincter in patients with oculomotor nerve palsies.

To evaluate the frequency and clinical correlates of preganglionic cholinergic supersensitivity of the iris sphincter, I prospectively tested 31 consecutive outpatients with oculomotor nerve palsies by comparing their pupil diameters in darkness before and 30 minutes after topical application of pilocarpine 0.1%. Supersensitive pupil responses were observed in the involved eye in five of 11 patients with compressive palsies, four of five patients with traumatic palsies, in the two patients with congenital palsies, and in none of the patients with ischemic palsies. Supersensitivity was statistically significantly associated with pupil involvement but not with aberrant regeneration of the extraocular muscles or pupil. The degree of supersensitivity was directly correlated with the amount of baseline anisocoria. These results establish that cholinergic supersensitivity of the pupil occurs frequently with nonischemic oculomotor nerve palsies and may be related to the degree of preganglionic injury to the pupillomotor fibers.