An anatomical anomaly in which the iris lies in a plane rather than bulging anteriorly. This is due to the fact that the root (or ciliary margin) of the iris is inserted more anteriorly into the ciliary body than is usual. On dilatation of the pupil the peripheral iris expands against the trabecular meshwork. It can predispose the eye to angle-closure glaucoma.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann