Glaucoma: Overview and Risk Factors

Glaucoma is a group of eye diseases characterized by optic nerve damage that is usually associated with elevated intraocular pressure. It can cause permanent visual field loss and possible blindness.¹ Glaucoma is the second–leading cause of blindness worldwide after cataract, but, unlike cataract, blindness caused by glaucoma is irreversible.

The four principal types of glaucoma are primary open–angle, angle closure, secondary, and congenital.

The most common form of this disease, primary open–angle glaucoma (POAG), is the focus of this chapter. This condition is an asymptomatic progressive process that can irreversibly affect peripheral visual fields and ultimately central vision. An ophthalmologic exam can diagnose glaucoma if elevated intraocular pressure or optic disc “cupping” is present, but cannot otherwise identify unaffected or at–risk eyes.

Angle–closure glaucoma generally occurs in an anatomically predisposed eye. As intraocular pressure mounts, the eye often becomes red and painful, but sometimes nausea is the principal symptom. Relief of the elevated pressure must occur emergently in most cases to avoid severe visual loss or blindness. Secondary glaucoma often results from cataract, inflammation, derangement of the eye anatomy due to blunt trauma, neovascularization in diabetic retinopathy, or central retinal vein occlusion.

Risk Factors

There are 4 major risk factors for POAG.²

• Age. There is <1% prevalence in persons under age 65, approximately 1% at 70 years, and 3% at 75 years.²
• Elevated intraocular pressure. However, high intraocular pressure is not necessary or sufficient for glaucoma pathogenesis.
• Race. Prevalence is 4 to 5 times greater in African Americans, compared with whites, and reaches 11% in African Americans aged 80 and over. The age–adjusted rate of blindness due to glaucoma is 6.6 times higher in African Americans, with blindness onset averaging 10 years earlier, compared with whites.^3,4
• Family history. There is a relative risk of 3.7 in siblings of the affected person and 2.2 in those with affected parents.⁵

Additional risk factors include:

• Use of corticosteroids.
• High blood pressure (a risk factor for elevated intraocular pressure).^6,7
• Diabetes.^6,8
• Homocysteine elevation .^9,10
• Low diastolic perfusion pressure.
• Cardiovascular disease.
• Hypothyroidism.
• Myopia.^11,12