This study is designed to develop a safe technique for creating a peripheral iridotomy with the Q-switched ruby laser in monkey and, later, in human eyes. The possible benefits and hazards of this technique will be evaluated and compared with those observed with the continuous wave argon laser. An investigation will also be made of the use of the Q-switched ruby laser to make openings (trabeculopuncture) in the trabecular meshwork or otherwise alter this tissue (gonio-photocoagulation) and increase the facility of aqueous outflow in the monkey eye. These studies will be extended to examine the usefulness of this technique in treatment of 42 persons with advanced open angle glaucoma. Histologic studies will be made to evaluate the monkey eyes at periodic intervals following laser iridotomy and gonio-photocoagulation using light microscopy, transmission and scanning electron microscopy.