Glaucoma, Chronic

Key Features

Essentials of Diagnosis

• Three types of chronic glaucoma: open-angle glaucoma, angle-closure glaucoma, and normal-tension glaucoma

• No symptoms in early stages

• Insidious progressive bilateral loss of peripheral vision, resulting in tunnel vision; visual acuities preserved until advanced disease

• Pathologic cupping of the optic disks

• Intraocular pressure is usually elevated

General Considerations

• Characterized by gradually progressive excavation ("cupping") of the optic disk with loss of vision progressing from slight visual field loss to complete blindness

• In chronic open-angle glaucoma, primary or secondary, intraocular pressure is elevated due to reduced drainage of aqueous fluid through the trabecular meshwork

• In chronic angle-closure glaucoma, flow of aqueous fluid into the anterior chamber angle is obstructed

• In normal-tension glaucoma, intraocular pressure is not elevated but the same pattern of optic nerve damage occurs

• Primary chronic open-angle glaucoma

  • Usually bilateral

  • Prevalence is increased in first-degree relatives of affected individuals and in diabetic patients

  • More frequent, occurs at an earlier age, and results in more severe optic nerve damage in

    • Afro-Caribbean persons

    • African persons

    • Hispanic persons

• Secondary chronic open-angle glaucoma may result from

  • Ocular disease, eg, pigment dispersion, pseudoexfoliation, uveitis, or trauma

  • Corticosteroid therapy, whether it is intraocular, topical, inhaled, intranasal, or systemic

Demographics

• In the United States, an estimated 2% of people over 40 years of age have glaucoma, affecting over 2.5 million individuals

  • At least 25% of cases are undetected

  • Over 90% of cases are of the open-angle type

• Worldwide, about 45 million people have open-angle glaucoma, of whom about 4.5 million are bilaterally blind

• About 4 million people, of whom approximately 50% live in China, are bilaterally blind from chronic angle-closure glaucoma

• Chronic angle-closure glaucoma is particularly common in Inuits and eastern Asians

Clinical Findings

• No symptoms initially; often first suspected at a routine eye test

• Optic disk cupping

  • Identified as an absolute increase or an asymmetry between the two eyes of the ratio of the diameter of the optic cup to the diameter of the whole optic disk (cup-disk ratio)

  • Cup-disk ratio > 0.5 or asymmetry between eyes of 0.2 or more is suggestive

• Visual field abnormalities initially develop in the paracentral region, followed by constriction of the peripheral visual field

• Intraocular pressure

  • The normal range of intraocular pressure is 10–21 mm Hg

  • In many individuals (about 4.5 million in the United States), elevated intraocular pressure is not associated with optic disk or visual field abnormalities (ocular hypertension)

  • Monitoring for the development of glaucoma is required in all such cases; a significant proportion of eyes with primary open-angle glaucoma have normal intraocular pressure when it is first measured, and only repeated measurements identify the abnormally high pressure

Diagnosis

• Diagnosis requires consistent and reproducible abnormalities in at ...