A YAG laser peripheral iridotomy is performed almost exclusively for patients with narrow angles, narrow angle glaucoma, or acute angle closure glaucoma. Aqueous fluid is made in the ciliary body of the eye, which is situated behind the iris. The aqueous fluid primarily escapes the eye by flowing between the lens and iris of the eye, and then drains via the trabecular meshwork, which is located in the angle of the eye (where the front clear cornea meets the iris, essentially). If the flow of aqueous fluid to the drainage angle is obstructed by a forwardly bowed iris, the patient is said to have narrow angles.
YAG PI involves creating a tiny opening in the peripheral iris, allowing aqueous fluid to flow from behind the iris directly to the anterior chamber of the eye. This typically allows an opening up of the angle of the eye. The narrow or closed angle thus becomes an open angle.
The procedure itself is completed with the patient seated at the laser, and requires no sedation. Topical anaesthesia eye drops are instilled, a lens is placed on the eye to better control the laser beam. In general, only a few very brief episodes of slight discomfort are associated with this procedure. However, generally there is no pain involved post operatively. The entire procedure takes only a few minutes.