Practice recommendations
- Screen persons older than 60 years, African Americans of any age, and those with a family history of open-angle glaucoma (C). Further evaluation by an ophthalmologist is warranted if optic nerve damage is suspected or if a patient reports decreasing vision.
- Elevated intraocular pressure (IOP) is not necessary for open-angle glaucoma to occur. Assess optic nerve status and visual field in those at risk. (C)
- Inquire about topical ocular drops recommended by an ophthalmologist, to be certain they are not contraindicated for other conditions the patient might have, and to be alert to the potential for adverse effects. (C)
Evaluate for open-angle glaucoma (OAG) when a patient reports decreased vision, or when a patient even with good eyesight is found to be at high risk for the disease. Most patients with early glaucoma are unaware of the initial decrease in peripheral vision.1
A relatively new diagnostic technique can detect even moderate damage to the optic nerve, and the procedure is brief. Ophthalmologists can choose from among several topical medications to reduce intraocular pressure. Your knowledge of the patient’s medical history is critical to avoiding potential drug-drug interactions.
Laser surgery and trabeculectomy may be indicated as first-line therapy for select patients.
Whom to screen
Persons aged older than 60 years, African Americans of any age, and those with a family history of OAG are at particularly high risk, and all risk factors should be fully assessed (SOR: B).2 (See Open-angle glaucoma: The scope of the problem.)
In the Caucasian population aged 40 to 49 years with no family history of OAG, disease prevalence is just 0.18%. Prevalence is 4 times greater in African Americans of the same age range. Caucasians aged 60 to 69 years have a prevalence of OAG 4 times greater than patients aged 40 to 49. For African Americans older than 80 years, prevalence exceeds 11%.3
For persons with a first-degree relative with OAG, risk was found to be 9.2 times greater than for those without such a history.8
Ask specifically about decreased vision, loss of peripheral vision, difficulty seeing in the dark, and difficulty reading (SOR: B).
Before referring high-risk patients for a full ophthalmologic examination, examine the optic nerve with direct ophthalmoscopy (SOR: B).
Open-angle glaucoma: The scope of the problem
Open-angle glaucoma (OAG) is defined as an optic neuropathy in which there is damage to the optic nerve with a loss of retinal ganglion cells that carry visual impulses from the eye to the brain. It is the second most common cause of legal blindness in the United States and the leading cause of blindness among African Americans.2 A population-based evaluation of glaucoma screening, the Baltimore Eye Survey, estimates about 2.5 million Americans as having OAG with as many as half of them unaware that they have the disease.3,4
More than 8 million office visits to office-based clinicians occur per year by patients with a primary diagnosis of glaucoma.5 The National Eye Institute, a division of the NIH, reports that as many as 120,000 Americans are currently blind as a result of glaucoma, costing the US government over $1.5 billion annually in Social Security benefits, lost income tax revenues, and health care expenditures.
An asymptomatic disease in its early stages,1 glaucoma progresses to cause permanent blindness in the absence of treatment. This article addresses the features, diagnostic methods, and treatment modalities of glaucoma as well as the role of the family physician in its management.
What causes OAG?
The pathogenesis of glaucoma is multifactorial and is thought, in most cases, to be caused by an abnormally high intraocular pressure (IOP), which mechanically compresses and causes subsequent atrophy of optic nerve fibers. The increased pressure is due to impaired drainage of aqueous humor out of the eye. Aqueous humor, produced by the ciliary body, normally provides nutrients to the iris, lens, and cornea before being drained through the trabecular meshwork.
It should be noted, however, that an elevated IOP is not necessary in glaucoma; optic nerve atrophy can occur in the absence of high IOP. The mechanism for optic nerve damage in this form of glaucoma is unknown.6
In angle-closure glaucoma, the angle between the iris and the trabecular meshwork is occluded, preventing normal drainage of aqueous humor. In open-angle glaucoma, the angle appears open but does not function properly in draining aqueous humor out of the eye.6 It is open-angle glaucoma that will be discussed here as it accounts for 75% to 95% of all glaucoma cases.7
Determining optic nerve status