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an·gle-clo·sure glau·co·ma(ang'gĕl-klō'zhŭr glaw-kō'mă)
Synonym(s): narrow-angle glaucoma.
glaucoma(glaw-ko'ma) [L., cataract]
Glaucoma occurs when the aqueous humor drains from the eye too slowly to keep up with its production in the anterior chamber. Thus, narrowing or closure of the filtration angle that interferes with drainage through the canal of Schlemm causes intraocular fluid to accumulate, after which intraocular pressure increases. Glaucoma may develop, however, even if the filtration angle is normal and the canal of Schlemm appears to be functioning; the cause of this form of glaucoma is not known.
Glaucoma may not cause symptoms. It is best detected early by measurements of elevated intraocular pressure (IOP), often made by adjusting the raw values that are obtained for changes in corneal thickness (as demonstrated with a pachymeter or with optical coherence tomography). A normal tonometer reading ranges from 13 to 22. The frequent need to change eyeglass prescriptions, vague visual disturbances, mild headache, and impaired dark adaptation may also be present. The standard for determining visual loss in glaucoma is the visual-field test.
Open-angle glaucoma causes mild aching in the eyes, loss of peripheral vision, haloes around lights, and reduced visual acuity (esp. at night) that is uncorrected by prescription lenses. Acute angle-closure glaucoma (an ophthalmic emergency) causes excruciating unilateral pain and pressure, blurred vision, decreased visual acuity, haloes around lights, diplopia, lacrimation, and nausea and vomiting due to increased IOP. The eyes may show unilateral circumcorneal injection, conjunctival edema, a cloudy cornea, and a moderately dilated pupil that is nonreactive to light. It requires immediate treatment to reduce IOP.
Nonoperative treatment includes the use of miotics (eserine, pilocarpine), timolol maleate, intravenous mannitol, and parenteral acetazolamide. Experimental studies indicate that marijuana alleviates the symptoms of severe glaucoma. Control of associated disorders such as diabetes mellitus should be maintained. Operative treatment includes laser trabiculoplasty, trabiculectomy, paracentesis of the cornea, iridectomy (broad peripheral), cyclodialysis, anterior sclerotomy, sclerotomy with inclusion of the iris, as iridotasis or iridencleisis; sclerectomy. See: illustration; ciliarotomy; trabeculoplasty
CAUTION!Acute glaucoma may be precipitated in patients with closed-angle glaucoma by dilating the pupils. In glaucoma patients, cycloplegic drops are given only after trabeculectomy and only in the eye that had the procedure. Administering drops in an eye affected with glaucoma can precipitate an acute attack in an eye already compromised by elevated IOP.
Health care providers should wash their hands thoroughly before touching the patient's eye. Prescribed topical and systemic medications are administered and evaluated.
The patient is prepared physically and psychologically for diagnostic studies and surgery as indicated. If the patient has a trabeculectomy, prescribed cycloplegic drugs are administered to relax the ciliary muscle and decrease iris action, thus reducing inflammation and preventing development of adhesions.
After any surgery, an eye patch and shield are applied to protect the eye, the patient is positioned with the head slightly elevated, and general safety measures geared to the patient's level of sensory alteration are instituted. Usually, the patient is encouraged to ambulate as soon as possible following surgery.
Patients with glaucoma need to know that the disease can be controlled, but not cured. Fatigue, emotional upsets, excessive fluid intake, and use of antihistamines may increase IOP. Signs and symptoms such as vision changes or eye pain should be reported immediately. Both the patient and family are instructed in correct techniques for hand hygiene and eyedrop administration; the importance of adherence to the prescribed regimen; the need for regular follow-up care with an ophthalmologist; and any adverse reactions to report.
Information is provided to the patient and family as needed. Referral is made to local organizations and support groups.
Public education is carried out to encourage glaucoma screening for early detection of the disease. Because glaucoma is more common in African Americans than European Americans, all African Americans above age 35 (and earlier for those with a family history of glaucoma) should have an annual tonometric examination. Written information should be made available about detection and control of glaucoma.