Atonic pupil after cataract surgery.

A dilated, atonic pupil is a recognized but unusual complication of cataract surgery. It appears to be a more common occurrence than the paucity of previously published reports would suggest. In this article, seven cases of post-cataract extraction atonic pupil are described. All patients underwent uneventful cataract extraction with posterior chamber intraocular lens (IOL) implantation. In all except one patient, there was a delay from the time of surgery to the development of the atonic pupil. Pharmacologic testing demonstrated that the site of the lesion was the iris sphincter. Possible pathogenic mechanisms are discussed.