The Effect of Iridotomy on Iris Contour

Abstract

With a recently developed technique for quantifying the geometry of the anterior chamber in optical cross section (slit-lamp photography using the Scheimpflug principle and computer correction for the optical effects of the cornea), we studied the iris contour before and after iridotomy in six patients with narrow anterior chamber angles and angle-closure glaucoma. Before iridotomy, the iris contour was convex anteriorly in all meridians. After iridotomy, the anterior lens surface position did not change perceptibly. The iris at the pupil margin settled backward onto the lens surface, no longer held forward by the narrow stream of aqueous passing from the posterior chamber to the anterior chamber. Next to the pupil there was often a perceptible mound, presumably representing the iris sphincter. From the point of support by the lens to the root of the iris, the contour of the iris surface was a straight line, except for the surface irregularities. The deepening of the anterior chamber at each point was the difference between the convex contour before iridotomy and the straight line after iridotomy.