Narrow Angle Glaucoma is a particular form of glaucoma where the trabecular meshwork of the eye, through which fluid exits the eye and keeps pressure in the normal range, is obstructed by the iris. The iris in susceptible individuals "bows forward" and covers up the trabecular meshwork in part or completely and can result in elevated pressures and damage to vision.
Chronic Narrow Angle Glaucoma
Chronic narrow angle glaucoma develops gradually, with the iris slowly over months and years becoming bowed forward and encroaching upon the trabecular meshwork of the eye where fluid exits the eye. This may result in slowly progressive elevation of pressures and can result in permanent closure of the angle which is more difficult to treat as it advances. This form of glaucoma is more common if the eye has a cataract because the cataract thickens behind the iris and causes the iris to be pressed forward.
Acute Narrow Angle Glaucoma
Acute narrow angle glaucoma develops where there is a sudden bowing-forward of the iris completely occluding the trabecular meshwork resulting in acutely high pressures. The pressures can rise to such a level that extreme pain is experienced along with redness, clouding of vision, perhaps rainbow-like effects when looking at lights, nausea, and vomiting. This is an ocular emergency and you should be seen by an ophthalmologist at once. This can be treated with an in-office laser procedure or surgery in the operating room.
Anatomically Narrow Angle
Sometimes at a routine eye examination the eye may be noted to have anatomically narrow angles. This means that the iris is in fact bowed forward but has not yet obstructed the trabecular meshwork. This places the eye at risk for chronic and acute angle closure glaucoma as described above. This condition is far better treated preventatively, i.e. before the disease develops into narrow angle glaucoma, and is performed with a laser in a procedure called iridotomy. The risk of this procedure is far less than the risk of developing painful acute angle closure glaucoma or insidious chronic angle glaucoma.