Effects of pilocarpine on the morphology of the human outflow apparatus.

The morphology of the outflow apparatus in human eyes which had been treated topically with either 2 or 4% pilocarpine on 4 occasions at 6-hourly intervals before enucleation was compared with an untreated control series of eyes from patients in a similar age range. In the pilocarpine-treated group the scleral spur was pulled posteriorly and internally, so that the angle formed by the scleral spur and the scleral sulcus was significantly greater in the treated than the untreated series. The change in attitude of the scleral spur produced widening of the spaces between the corneoscleral trabeculae and distension of the endothelial meshwork. It was shown from counts of giant vacuoles in the endothelium of Schlemm's canal that the incidence of giant vacuoles in the pilocarpine-treated group was greater than twice that in the controls. It would appear that pilocarpine produces alterations in the configuration of the outflow apparatus which would promote the drainage of aqueous humour.