Primary Open-Angle Glaucoma - Guidelines Spotlight (Glaucoma Awareness Month)

Primary Open-Angle Glaucoma – Guidelines Spotlight (Glaucoma Awareness Month)

Published on January 8, 2025

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Glaucoma is a chronic optic neuropathy characterized by progressive damage to the optic nerve and retinal nerve fiber layer (RNFL), which can result in permanent vision loss. It is a prevalent condition, affecting approximately 3 million Americans and ranking as the second leading cause of blindness globally, according to the Centers for Disease Control (CDC).

The most common form of glaucoma is primary open-angle glaucoma (POAG), which is associated with increased eye pressure. Unfortunately, early symptoms are often asymptomatic, leading to a significant portion of individuals being unaware of their condition. While there is currently no cure for glaucoma, early detection can help preserve vision and prevent further vision loss.

The American Optometric Association (AOA) recently released guidelines for the Care of the Patient with Primary Open-Angle Glaucoma on October 28, 2024. In many communities across the United States, doctors of optometry are the sole provider and often a patient’s first entry point into the health care system. The AOA’s guideline provides recommendations for examination, treatment, and management strategies to help maintain vision and improve the quality of life for individuals with POAG.

In this discussion and for Glaucoma Awareness Month 2025, we will delve into the key takeaways and insights surrounding the guideline’s recommendations for POAG. Please note that this list does not encompass all major points. For a complete list of recommendations, refer to the summary located here or the full text guideline located here on the AOA website.

Key Takeaways

Screening

The issue of screening for glaucoma is a topic of debate within the medical community. The United States Preventive Services Task Force (USPSTF) conducted a thorough review of published literature in order to assess the potential benefits and drawbacks of glaucoma screening. After careful analysis, the USPSTF determined that there is currently insufficient evidence to fully evaluate the advantages and disadvantages of screening asymptomatic adults for glaucoma.

While screening tests have the ability to detect individuals with glaucoma, treatment has been shown to reduce the risk of glaucoma progression. However, there is a lack of evidence demonstrating improvements in visual outcomes, quality of life, and overall function as a result of treatment. Additionally, the cost-effectiveness of glaucoma screening has not been established. Even when patients are suspected of having POAG, many fail to follow up with necessary examinations or care, despite the potential benefits of treatment in reducing the risk of glaucoma progression.

Risk Factors

Modifiable Risk Factors

Numerous studies have confirmed that elevated intraocular pressure (IOP) is a significant risk factor for the development of POAG. The Early Manifest Glaucoma Trial (EMGT) indicated that any increase in IOP is a strong predictor of glaucoma progression.

Non-Modifiable Risk Factors

In addition to elevated IOP, there are several non-modifiable risk factors that have been associated with the development of POAG. These include age, race, genetics, type 2 diabetes, and hypertension, among others.

Examination

When evaluating a patient suspected of having POAG, it is crucial to conduct a thorough and comprehensive eye and vision examination. This examination should focus on assessing various aspects, including the anterior chamber angle, optic nerve head (ONH), peripapillary retinal nerve fiber layer (RNFL), macula, visual fields (VF), as well as measuring IOP and central corneal thickness (CCT). By thoroughly examining these key areas, healthcare professionals can accurately diagnose and manage POAG in patients.

Treatment Options

Prostaglandin Analogues

Prostaglandin analogues are often considered the initial therapy for lowering intraocular pressure (IOP) and have been found to provide the most effective IOP-lowering among all monotherapy topical drugs. When combined with another category of topical drug, prostaglandin analogues further enhance the decrease in IOP. These analogues work by increasing uveo-scleral outflow and reducing IOP by approximately 25% to 30%.

Due to their generally good IOP-lowering effectiveness, limited systemic and ocular side effects, and once-daily dosing at bedtime (HS), prostaglandin analogues have become the “first-line” treatment for many types of glaucoma.

Beta-Blockers

Beta-blockers are commonly used to reduce IOP by decreasing the production of aqueous humor. These medications work by inhibiting ultrafiltration in the ciliary body, which in turn limits the secretion of aqueous humor. Ophthalmic beta-blockers can be classified as either non-selective, which inhibit both beta1 and beta2 receptors, or cardio-selective, which primarily inhibit beta1 receptors over beta2 receptors. Non-selective beta-blockers are more effective at lowering IOP but may also cause more systemic side effects.

Common beta-blockers used in ophthalmology include timolol maleate, levobunolol, metipranolol, and betaxolol HCL. While ocular side effects are typically mild, they may include dry eye, lid ptosis, conjunctival hyperemia, corneal anesthesia, and blurred vision. It is important to note that non-selective beta-blockers should be avoided in patients with certain conditions such as asthma, chronic obstructive pulmonary disease, atrioventricular block, bradyarrhythmia, unstable congestive heart failure, depression, myasthenia gravis, diabetes mellitus with a history of hypoglycemic events, or patients using calcium channel blockers.

Adrenergic Agonists

Adrenergic agonists are medications that target both alpha- and beta-adrenergic receptors, impacting the IOP by reducing aqueous formation and resistance at the trabecular meshwork (TM). Examples of alpha-adrenergic agonists currently available include brimonidine tartrate and apraclonidine HCL.

Carbonic Anhydrase Inhibitors

Carbonic anhydrase inhibitors (CAIs) work by lowering IOP through the suppression of aqueous production. This is achieved by blocking carbonic anhydrase in local tissues, leading to an increase in CO2 levels and/or a decrease in pH. This process results in vascular dilation and increased fluid flow. Common CAIs include acetazolamide, brinzolamide, dorzolamide HCL, and methazolamide.

Selective Laser Trabeculoplasty (SLT)

SLT is a viable alternative or complementary therapy to medication for controlling IOP. A comprehensive review of published studies has shown that SLT therapy is comparable to medication-only treatment in reducing IOP and achieving successful IOP control. Additionally, SLT has been found to significantly reduce the average number of medications required. Long-term follow-up studies have demonstrated that SLT is a safe procedure, making it a potential first-line therapy option for OAG.

Surgical Interventions

Surgical treatment is considered when IOP cannot be adequately lowered through medical or laser therapy. In cases of advanced damage, uncontrolled IOP, or rapid progression of POAG, surgery may be the most appropriate initial treatment. Surgical intervention has been shown to significantly decrease the incidence and speed of VF progression in glaucoma patients who have shown progression before surgery. Additionally, it may prevent further VF progression in eyes with inadequate IOP control prior to surgery.

Please note, the guideline emphasizes the importance of carefully managing pregnant patients with primary open-angle glaucoma (POAG) in order to balance the risk of glaucoma progression with the safety of the fetus. It is important to collaborate with the patient’s obstetrician and neonatologist to ensure comprehensive care. When considering pharmacological treatment for glaucoma during pregnancy and lactation, it is essential to adhere to the safety profiles outlined by the United States Food and Drug Administration (FDA) and take into account the severity of the glaucoma and the stage of pregnancy.

This guideline is designed to enhance patient outcomes by offering a thorough approach to diagnosing, managing, and treating POAG.

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