Author: Jeannette Y. Wick, RPh, MBA, FASCP
Pharmacists can play an important role in ensuring adherence to medication for glaucoma patients to help them avoid irreversible vision loss.
Glaucoma is an umbrella term that describes disturbances of the optic nerve’s structural or functional integrity leading to atrophic changes. Glaucoma affects more than 2.2 million Americans and nearly 2% of Americans older than age 40. Approximately 15% of all cases of blindness are linked to the disease.
Health care clinicians often associate glaucoma with increased intraocular pressure (IOP), usually greater than 20 mm Hg. However, a small subset of patients has normal-tension or low-tension glaucoma, in which IOP is normal, but the disease progresses regardless. Additionally, some patients have elevated IOP, but never develop signs or symptoms of the disease. We focus on IOP, however, because to date, it’s the only risk factor we have been able to modify.
Included under the umbrella term are 2 types of glaucoma
Primary open-angle glaucoma (POAG) is an acquired, chronic, progressive optic neuropathy with characteristic optic nerve fiber loss. It is called “open” because the eye’s anterior chamber angles—the area between the iris and cornea, through which fluid flows to escape via the trabecular meshwork—remain open. IOP is usually elevated, and causes optic disc cupping and atrophy. As patients age and retinal ganglion cell (RGC) damage accumulates slowly and insidiously, they may develop specific visual field defects up to and sometimes including complete loss of vision. Because vision loss occurs gradually, patients may not seek help until significant impairment has occurred. This vision loss is irreversible. Approximately 90% of all glaucoma cases are classified as POAG.
Closed-angle (or angle closure) glaucoma usually occurs suddenly, and is accompanied by great pain, rapid change in vision, nausea, and vomiting. Patients generally seek emergency treatment quickly.
As one of the leading preventable causes of blindness, POAG is a global health problem. Appropriate screening with an annual dilated eye exam and treatment with drugs or surgery can stop glaucoma’s progress before significant vision loss occurs.
The exact cause of glaucoma is unknown, but elevated IOP, family history, race, age older than 40 years, and myopia are all risk factors. A review article
published in the March 2012 edition of Ophthalmology
reports that some researchers are changing their thinking about glaucoma. Their theories classify it as less of an eye disease and more of a central neurologic disorder like Parkinson’s disease and Alzheimer's disease. They postulate that changes in the brain lead to RGC degeneration and death.
“As researchers turn their attention to the mechanisms that cause retinal ganglion cells to degenerate and die, they are discovering ways to protect, enhance, and even regenerate these vital cells,” said the article’s lead author, Jeffrey L. Goldberg, MD, PhD, assistant professor of ophthalmology at the Bascom Palmer Eye Institute and Interdisciplinary Stem Cell Institute, in a press release. “Understanding how to prevent damage and improve healthy function in these neurons may ultimately lead to sight-saving treatments for glaucoma and other degenerative eye diseases.”
Interventions aimed at RGCs may be our best hope for preventing and potentially curing glaucoma. As researchers pursue this line of thinking, we must continue to use available tools to help patients.
Glaucoma patients are frequent pharmacy customers as medication is the cornerstone of treatment for those with elevated IOP. When IOP exceeds 21 mm Hg, visual field loss increases rapidly. A patient with an IOP of 28 mm Hg is approximately 15 times more likely to develop field loss than a patient with an IOP of 22 mm Hg. This highlights an important treatment consideration: depending on the patient’s type of glaucoma and level of IOP, he or she may need more aggressive treatment. Patients often struggle with adherence to the topical and systemic medications prescribed by ophthalmologists. However, since loss of vision due to glaucoma is currently irreversible, pharmacists should emphasize to patients that strict adherence is crucial.
This Condition Center will explore glaucoma, the many theoretical explanations for its pathogenesis, and most important, the pharmacologic agents used to treat it. Welcome, and be sure to check in for updates. To start, check out our other inaugural posts:
Glaucoma: To Screen or Not to Screen
Eye Drop Adherence: Waste, Contamination, Inaccuracy
Recreational Drug Use: A Risk Factor for Glaucoma?
Intraocular Pressure Insights
Three Blind Mice? Maybe Not
Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy and a freelance writer from Virginia.