narrow-angle glaucoma

an·gle-·clo·sure glau·co·ma

primary glaucoma in which contact of the iris with the peripheral cornea excludes aqueous humor from the trabecular drainage meshwork. Synonym(s): acute glaucoma, closed-angle glaucoma, narrow-angle glaucoma

an·gle-clo·sure glau·co·ma

(ang'gĕl-klō'zhŭr glaw-kō'mă) Primary glaucoma in which contact of the iris with the peripheral cornea excludes aqueous humor from the trabecular drainage meshwork; may develop in either eye or both.
Synonym(s): narrow-angle glaucoma.

glaucoma

(glaw-ko'ma) [L., cataract]

GLAUCOMA

GLAUCOMA

GLAUCOMAA group of eye diseases characterized by increased intraocular pressure, resulting in atrophy of the optic nerve. Glaucoma causes gradual loss of peripheral vision, and ultimately, blindness. Glaucoma is the third most prevalent cause of visual impairment and blindness in the U.S, although the incidence of blindness is decreasing due to early detection and treatment. An estimated 15 million residents of the U.S. have glaucoma; of these, 150,000 have bilateral blindness. The three major categories of glaucoma are narrow- or closed-angle (acute) glaucoma, which occurs in persons whose eyes are anatomically predisposed to develop the condition; open-angle (chronic) glaucoma, in which the angle that permits the drainage of aqueous humor from the eye seems normal but functions inadequately due to overproduction of aqueous humor or outflow obstruction through the trabecular meshwork or the canal of Schlemm; and congenital glaucoma, in which intraocular pressure is increased because of an abnormal fluid drainage angle (which may result from congenital infections, Sturge-Weber syndrome, or prematurity-related retinopathy), or for an unknown reason. The increased pressure causes the globe of the eye to be enlarged, a condition known as buphthalmia. The acute type of glaucoma often is attended by acute pain. The chronic type has an insidious onset. An initial visual dysfunction is loss of the mid-peripheral field of vision. The loss of central visual acuity occurs later in the disease. See: visual field for illus.

Etiology

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.

Diagnosis

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.

Treatment

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.

Patient care

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.

absolute glaucoma

End-stage glaucoma, that is, glaucoma that produces a complete loss of vision. Upon examination, the optic nerve appears pale.

chronic glaucoma

Glaucoma in which the tonometer indicates an intraocular pressure reading of up to 45 or 50, the anterior ciliary veins are enlarged, the cornea is clear, the pupil is dilated, and pain is present. During attacks vision is poor. The visual field may be normal. Cupping of the optic disk is not present in the early stages.

closed-angle glaucoma

Glaucoma caused by a shallow anterior chamber and thus a narrow filtration angle through which the aqueous humor normally passes. Because the rate of movement of the aqueous humor is impaired, intraocular pressure increases. In general, headache, haloes around single sources of light, blurred vision, and eye pain are symptomatic. Synonym: narrow-angle glaucoma

low-tension glaucoma

A type of glaucoma in which intraocular pressures are normal (less than 22 mm Hg).

narrow-angle glaucoma

Closed-angle glaucoma.

pigmentary glaucoma

Glaucoma produced by the dispersion of organic pigment from the zonula ciliaris to the trabecular meshwork of the eye.

primary open-angle glaucoma

The most common type of glaucoma. It usually affects both eyes, and there is a characteristic change in the appearance of the optic disk. The cup (the depression in the center of the disk) is enlarged. Visual loss is determined by the visual-field test. Many patients with glaucoma have increased intraocular pressure but this is not considered essential to the diagnosis because some patients have normal intraocular pressure.

secondary glaucoma

Glaucoma caused by ocular trauma or an underlying disease that affects the eye.

narrow-angle glaucoma

A condition of raised fluid pressure within the eye resulting from obstructed access of aqueous humour to the drainage channel (the trabecular meshwork) at the root of the IRIS. This occurs because the angle between the iris and the back of the CORNEA is narrower than normal and can easily close, especially when the pupil is wide and the iris consequently bunched up.

单词	narrow-angle glaucoma
释义	DictionarySeeangle-closure glaucoma narrow-angle glaucoma narrow-angle glaucoma [′nar·ō ¦aŋ·gəl glau̇′kō·mə] (medicine) Increased intraocular tension due to a block of the angle of the anterior chamber from contact of the iris by the trabecula. Also known as obstructive glaucoma. narrow-angle glaucoma an·gle-·clo·sure glau·co·ma primary glaucoma in which contact of the iris with the peripheral cornea excludes aqueous humor from the trabecular drainage meshwork. Synonym(s): acute glaucoma, closed-angle glaucoma, narrow-angle glaucoma an·gle-clo·sure glau·co·ma (ang'gĕl-klō'zhŭr glaw-kō'mă) Primary glaucoma in which contact of the iris with the peripheral cornea excludes aqueous humor from the trabecular drainage meshwork; may develop in either eye or both. Synonym(s): narrow-angle glaucoma. glaucoma (glaw-ko'ma) [L., cataract] GLAUCOMAGLAUCOMAGLAUCOMAA group of eye diseases characterized by increased intraocular pressure, resulting in atrophy of the optic nerve. Glaucoma causes gradual loss of peripheral vision, and ultimately, blindness. Glaucoma is the third most prevalent cause of visual impairment and blindness in the U.S, although the incidence of blindness is decreasing due to early detection and treatment. An estimated 15 million residents of the U.S. have glaucoma; of these, 150,000 have bilateral blindness. The three major categories of glaucoma are narrow- or closed-angle (acute) glaucoma, which occurs in persons whose eyes are anatomically predisposed to develop the condition; open-angle (chronic) glaucoma, in which the angle that permits the drainage of aqueous humor from the eye seems normal but functions inadequately due to overproduction of aqueous humor or outflow obstruction through the trabecular meshwork or the canal of Schlemm; and congenital glaucoma, in which intraocular pressure is increased because of an abnormal fluid drainage angle (which may result from congenital infections, Sturge-Weber syndrome, or prematurity-related retinopathy), or for an unknown reason. The increased pressure causes the globe of the eye to be enlarged, a condition known as buphthalmia. The acute type of glaucoma often is attended by acute pain. The chronic type has an insidious onset. An initial visual dysfunction is loss of the mid-peripheral field of vision. The loss of central visual acuity occurs later in the disease. See: visual field for illus. Etiology 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. Diagnosis 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. Treatment 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. Patient care 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. absolute glaucoma End-stage glaucoma, that is, glaucoma that produces a complete loss of vision. Upon examination, the optic nerve appears pale. chronic glaucoma Glaucoma in which the tonometer indicates an intraocular pressure reading of up to 45 or 50, the anterior ciliary veins are enlarged, the cornea is clear, the pupil is dilated, and pain is present. During attacks vision is poor. The visual field may be normal. Cupping of the optic disk is not present in the early stages. closed-angle glaucoma Glaucoma caused by a shallow anterior chamber and thus a narrow filtration angle through which the aqueous humor normally passes. Because the rate of movement of the aqueous humor is impaired, intraocular pressure increases. In general, headache, haloes around single sources of light, blurred vision, and eye pain are symptomatic. Synonym: narrow-angle glaucoma low-tension glaucoma A type of glaucoma in which intraocular pressures are normal (less than 22 mm Hg). narrow-angle glaucoma Closed-angle glaucoma. pigmentary glaucoma Glaucoma produced by the dispersion of organic pigment from the zonula ciliaris to the trabecular meshwork of the eye. primary open-angle glaucoma The most common type of glaucoma. It usually affects both eyes, and there is a characteristic change in the appearance of the optic disk. The cup (the depression in the center of the disk) is enlarged. Visual loss is determined by the visual-field test. Many patients with glaucoma have increased intraocular pressure but this is not considered essential to the diagnosis because some patients have normal intraocular pressure. secondary glaucoma Glaucoma caused by ocular trauma or an underlying disease that affects the eye. narrow-angle glaucoma A condition of raised fluid pressure within the eye resulting from obstructed access of aqueous humour to the drainage channel (the trabecular meshwork) at the root of the IRIS. This occurs because the angle between the iris and the back of the CORNEA is narrower than normal and can easily close, especially when the pupil is wide and the iris consequently bunched up.
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