The intraocular fluid (aqueous humor) is continuously secreted from the blood into the eye, cleansing and bringing vital nourishment to the eye’s inner structures. The fluid then exits from the eye, returning to the blood stream. The unimpeded circulation of this intraocular fluid is essential to good ocular health. The anterior chamber is the fluid-filled compartment within the eye just in front of the pupil. Viewed in profile, the anterior chamber is bounded by the domed cornea in front and by the colored iris behind. Where the two converge they form an angle containing the channels which drain fluid from the eye.
The anterior chamber angle may vary considerably in width and still remain open, permitting normal outflow of fluid. A narrow anterior chamber angle, however, is a potentially dangerous condition. This anatomic abnormality results if the iris (colored tissue surrounding the pupil) is bowed forward toward the cornea (the eye’s transparent front “window”), narrowing the distance between the two.
In people having narrow anterior chamber angles, under certain circumstances — pupil dilation, for example — the iris may actually contact the adjacent cornea, closing the anterior chamber angle and interrupting the normal outflow of fluid from the eye. This is a serious eye emergency known as acute angle closure. Acute angle closure is marked by a sudden and painful elevation of the intraocular fluid pressure (IOP) to levels endangering the health of the optic nerve and, without prompt medical or surgical intervention, rapidly progressing to permanent loss of vision (glaucoma).
By contrast, the much more common condition called open angle glaucoma usually results from a very prolonged but more limited elevation of IOP causing few if any early symptoms before vision loss results.
Because of its real threat to vision, once narrow anterior chamber angles are diagnosed and the risk of angle closure glaucoma determined, preventive treatment is advisable. A quick and simple laser procedure (peripheral iridotomy) to create a microscopic opening in the iris is highly effective in markedly reducing this risk.
The iris opening serves as a “relief valve” which equalizes fluid pressure behind and in front of the iris, averting angle closure.
The laser procedure itself causes little sensation. Side effects, if any, may include transient blurring of vision, mild inflammation, temporary elevation of IOP and, less commonly, minimal bleeding at the treatment site. Eye drops are used immediately prior to treatment and for several days thereafter to control inflammation and minimize IOP rise. The small potential for side effects of laser treatment is far outweighed by the serious consequence of angle closure glaucoma if narrow anterior chamber angles are left untreated.