Glaucoma and dry eye disease (DED) are two distinct conditions that frequently appear together in patients. While glaucoma itself does not cause DED, the necessary treatments for glaucoma often induce or worsen DED symptoms. A significant percentage of people undergoing long-term glaucoma therapy will experience uncomfortable ocular surface issues, making it essential to understand the separate origins of each disease for effective management.
Separating Glaucoma and Dry Eye Disease
Glaucoma is a progressive disease that damages the optic nerve, the main conduit connecting the eye to the brain, which can lead to irreversible vision loss. This damage is typically associated with elevated pressure inside the eye, known as intraocular pressure (IOP). Glaucoma is a disorder of the deep structures of the eye, specifically the nerve and the internal fluid dynamics.
Dry eye disease, in contrast, is a chronic condition affecting the eye’s surface, resulting from either insufficient tear production or accelerated tear evaporation. Tears are a complex mix of water, oil, and mucus, and DED occurs when this tear film becomes unstable. This instability causes irritation, a gritty sensation, and sometimes paradoxically, excessive watering.
The prevalence of both conditions increases with age, which is one reason they often coexist in the same patient. Studies suggest that between 40% and 60% of patients being treated for glaucoma also have DED, a rate substantially higher than in the general population.
How Glaucoma Treatments Lead to Dry Eyes
The primary reason for the high co-occurrence of DED is the long-term use of topical eye drops necessary to control glaucoma. These drops contain active ingredients to lower IOP, but they also often contain preservatives that are toxic to the delicate ocular surface. Benzalkonium Chloride (BAK) is the most common preservative used in ophthalmic preparations, and it is a major contributor to DED in this patient group.
BAK is a detergent that helps maintain the sterility of the drops, but its chemical nature can damage the epithelial cells on the cornea and conjunctiva. It also destabilizes the tear film by disrupting the lipid layer that prevents tears from evaporating too quickly. The resulting local inflammation and cell damage manifest as dry eye symptoms.
Glaucoma is a lifelong condition, requiring daily, often multiple-times-a-day, application of these drops over many years. This chronic, cumulative exposure to BAK leads to a worsening of the ocular surface disease over time, often causing a significant reduction in the density of specialized cells, like goblet cells, which are needed for tear film health. Even the active drug ingredients can contribute to irritation; for example, carbonic anhydrase inhibitors can cause burning on instillation due to their acidic pH. Other classes, like alpha-agonists, may cause dry mouth and nose, which can reduce tear production.
Strategies for Managing Ocular Surface Side Effects
Managing ocular surface side effects is an important part of glaucoma care because the discomfort can negatively affect a patient’s adherence to their vision-saving medication. Reducing the patient’s exposure to BAK is the primary strategy. Preservative-free (PF) glaucoma drop formulations or those using less toxic preservatives offer an alternative to traditional BAK-containing drops.
Another approach is to utilize non-topical treatments for glaucoma, such as selective laser trabeculoplasty (SLT) or sustained-release drug implants, which bypass the need for daily drops altogether. These options can significantly reduce the toxic load on the ocular surface while still maintaining IOP control.
Standard dry eye therapies are also used alongside glaucoma drops to mitigate symptoms. These include frequent use of lubricating artificial tears, with a strong recommendation for preservative-free tears to avoid adding more BAK exposure. Prescription anti-inflammatory drops, such as cyclosporine, can be used to treat the underlying inflammation caused by the chronic use of preserved glaucoma drops. These medications help restore the health of the ocular surface.
Patients must remember that glaucoma is a sight-threatening disease, and IOP control remains the priority. It is necessary to consult with an eye care professional before making any changes to the glaucoma treatment regimen, even when managing irritating dry eye symptoms. The goal is a carefully balanced approach that preserves vision while maximizing patient comfort.