Glaucoma is a group of ocular diseases characterized by optic nerve damage, which can lead to vision loss and blindness. Glaucoma affects three million Americans and is the second leading cause of blindness in the United States. However, half of the people with glaucoma don't know they have it. While there is no known cure for glaucoma, routine screening and preventive treatment can preserve vision and eye health. This article will discuss a functional medicine approach to preventing and treating glaucoma. (1)
What is Glaucoma?
Glaucoma is a group of diseases that cause vision loss and blindness by damaging the optic nerve. In most cases, fluid builds up in the front part of the eye, which increases intraocular pressure (IOP) and damages the nerve. Most people with glaucoma have it in both eyes, but one eye may be more severely affected than the other. (2, 4)
There are many types of glaucoma, classified as either primary (unrelated to another medical condition) or secondary (caused by an underlying medical condition). Primary glaucoma is more common than secondary glaucoma. (3)
The main forms of primary glaucoma include:
Open-angle is the most common type of glaucoma in the United States, affecting 90% of Americans with glaucoma. Open-angle glaucoma occurs when fluid drains too slowly through the eyes' drainage canals, despite normal anatomy. Over time, increased IOP damages the optic nerve and decreases vision. (3, 4)
Also called angle-closure glaucoma, this is an acute and emergent form of glaucoma that occurs when the angle between the iris and cornea blocks fluid from draining out of the front portion of the eye. Fluid in the eye quickly builds and causes a sudden increase in IOP. (3, 4)
Normal-tension glaucoma is a subtype of open-angle glaucoma that occurs with normal eye pressure. (4)
Congenital glaucoma affects 1 in 10,000 babies born in the United States. This type of glaucoma occurs when the eyes' drainage canals don't form properly during fetal development. (3, 4)
Glaucoma Signs & Symptoms
Open-angle glaucoma doesn't present with warning signs or symptoms in its early stages, making it a "silent thief of sight." As the disease progresses, peripheral painless vision loss occurs. Uncontrolled forms of open-angle glaucoma will result in central vision loss and blindness. (5, 6)
Closed-angle glaucoma attacks present with severe eye and forehead pain, eye redness, vision loss and blurred vision, visual halos, headache, nausea, and vomiting. Patients experiencing these symptoms require immediate medical attention to prevent permanent vision loss. (5)
Children born with congenital glaucoma usually present with immediate signs and symptoms, including cloudy eyes, light sensitivity, increased tear production, and larger-than-normal eyes (3).
What Causes Glaucoma?
The exact cause of glaucoma is unknown, but there is a clear correlation between IOP and the development of glaucoma. In a healthy eye, eye fluids (called aqueous humor) flow through the pupil to the front of the eye and then drain through canals between the iris and cornea. With glaucoma, drainage resistance develops in these canals, and excess fluid that builds up puts pressure on the optic nerve, causing damage over time.
Errors in collagen metabolism and resulting impaired structural composition of the eye can induce eye changes that impair aqueous humor and blood flow through and to the eye. These changes can result in elevated IOP and vision loss. (7)
Hypothyroidism, a prevalent endocrine disease characterized by low thyroid hormones, increases the risk of developing primary open-angle glaucoma. It is suggested that the increased IOP seen in hypothyroidism is caused by mucopolysaccharide deposition in the eyes, resulting in reduced aqueous humor outflow. (8)
Other important risk factors for developing glaucoma include (4, 6):
- Age over 55
- Race and ethnicity: people of Black, Asian, and Hispanic heritage are more likely to develop glaucoma
- Family history of glaucoma
- Medical conditions: diabetes, hypertension, sickle cell anemia, migraines
- Chronic use of corticosteroids
- Extreme nearsightedness (increased risk of open-angle glaucoma) or farsightedness (increased risk of closed-angle glaucoma)
- History of eye injury or surgery
Functional Medicine Labs to Test for Root Cause of Glaucoma
Evaluation for glaucoma requires a comprehensive dilated eye examination that includes measuring intraocular pressure (tonometry), visual field testing, measuring corneal thickness (pachymetry), and inspecting the drainage angle (gonioscopy). A glaucoma diagnosis is made based on characteristic clinical and physical exam findings. (2)
Functional medicine labs help practitioners personalize treatment options for their patients. Below are some of the most common labs ordered for patients suffering from glaucoma.
Fasting blood glucose, insulin, and hemoglobin A1c (HbA1c) can be ordered to comprehensively assesses blood sugar regulation. Elevated levels are associated with hyperglycemia, insulin resistance, and diabetes mellitus.
A thyroid panel, including TSH, free T4, and free T3, can diagnose hypothyroidism. Hypothyroidism is associated with elevated TSH levels and low free T4 and/or free T3 levels.
A comprehensive micronutrient test can identify deficiencies in vitamins and minerals important in maintaining eye health. This test's results can help personalize a nutritional and supplemental treatment based on the patient's nutritional status.
Conventional Treatment for Glaucoma
Conventional therapy consists primarily of medications to lower IOP to less than 21 mmHg to slow vision loss. Typical pharmacologic agents for treating glaucoma include beta-blockers, alpha-agonists, and miotic agents. Occasionally, laser therapy or surgery is performed to improve aqueous outflow. (8)
Functional Medicine Treatment Protocol for Glaucoma
Functional medicine doctors can prescribe a personalized evidence-based treatment plan for glaucoma that includes dietary and supplemental recommendations based on an extensive intake and lab results.
Medical conditions that increase the risk of glaucoma need to be managed appropriately. This article will not discuss these protocols, but they can be found in the Rupa Health Magazine.
Therapeutic Diet and Nutrition Considerations for Glaucoma
Healthy dietary choices provide the body with the nutrients it needs to support eye health, protect against oxidative stress that causes tissue damage, and mediate cardiovascular risk factors for glaucoma. Fruits, vegetables, nuts, and seeds are good sources of vitamins A, C, E, lutein, and zeaxanthin, known to combat oxidative stress that damages the optic nerve. Research suggests that consuming at least three servings of fruits and vegetables daily can lower the risk of glaucoma by 79%. In particular, green leafy vegetables appear to be particularly beneficial in reducing the risk of glaucoma.
The Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet is associated with a lower incidence of open-angle glaucoma and can be recommended to prevent neurodegeneration of the eye. The MIND diet guidelines are as follows:
Foods to Include in the Diet
- At least three servings of whole grains daily
- At least one serving of non-green leafy vegetables daily
- At least six servings of green leafy vegetables weekly
- At least five servings of nuts weekly
- Include beans in at least four meals weekly
- At least two servings of berries weekly
- Include poultry in at least two meals weekly
- Include fish in at least one meal weekly
- Use olive oil as the primary source of fat
Foods to Limit in the Diet
- Less than five servings of pastries and sweets weekly
- Less than four servings of red meat (i.e., beef, pork, lamb) weekly
- Less than one serving of cheese and fried foods weekly
- Less than one tablespoon of butter/margarine daily
Ingestion of a single serving (200-360 mL) of caffeinated coffee causes transient elevations in IOP. Additionally, research suggests that drinking large amounts of caffeine daily (480 mg or four cups of coffee) increases the risk of glaucoma more than three-fold in those with a genetic predisposition to elevated IOP. Based on these findings, it is reasonable to recommend a trial of caffeine avoidance for 4-6 weeks to determine the effects of caffeine elimination on IOP. Consider replacing your caffeinated beverages with decaffeinated tea; according to one study, patients who drink at least one cup of hot tea daily lowered their risk of glaucoma by 74%.
Supplements Protocol for Glaucoma
Below are some evidence-based nutritional and herbal supplements to consider incorporating into your patient's nonpharmacologic treatment plan for glaucoma.
Ginkgo (Ginkgo biloba) is rich in terpenoids and flavonoids, which are responsible for its many health benefits, including antimicrobial, anti-inflammatory, platelet inhibitor, antioxidant, and vasodilator. Its ability to quench free radicals and improve blood flow to the eyes makes it a safe and valuable herb in treating glaucoma long-term and preventing vision loss. (9-11)
Dose: 40 mg three times daily
Glutathione is often called the body's "master antioxidant" because it dampens oxidative damage and mitigates numerous diseases. Depletion of glutathione is associated with neurodegeneration and the development of eye diseases (12, 13).
Dose: compounded eye drops 1 mg/mL; apply two drops in each eye once daily
Anthocyanins are a type of plant flavonoid responsible for plants' deep red, purple, and blue pigments. Flavonoid-rich extracts can prevent free radical damage and improve blood vessel and collagen integrity. Research also shows that anthocyanins can reduce blood pressure and prevent neurological disease. The Fruit Anthocyanins concentrate formulated by Dr. William Mitchell is a popular supplement among functional doctors for treating glaucoma. (14)
Dose: 1 tbsp once daily
Magnesium deficiency has been identified in patients with glaucoma and is associated with antioxidant imbalances, increased inflammation, and increased formation of fibrous tissues intraocularly. Magnesium supplementation can reduce blood pressure and has been shown to improve visual field defects in glaucoma patients. (15)
Dose to bowel tolerance at three times daily dosing.
Vitamin C plays a critical role in maintaining a healthy collagen network, is a potent antioxidant, and has been shown to lower IOP in several clinical studies.
Dose to bowel tolerance at three times daily dosing.
When to Retest Labs
Reductions in IOP have been measured as early as four weeks after initiating a glaucoma treatment plan like the one described above. If no changes to symptoms or IOP are observed at this time, it would be reasonable to revise the treatment plan. Long-term adherence to glaucoma treatment plans is often required to maintain normal IOP.
Glaucoma is a neurodegenerative eye disease typically related to increased intraocular pressure and can potentially cause irreversible vision loss and blindness. Open-angle glaucoma is the most common type of glaucoma and usually doesn't present with any symptoms until optic nerve damage has occurred. A healthy diet, the management of chronic cardiovascular diseases, and regular eye exams are important in preventing glaucoma-related vision loss. An integrative treatment protocol may include pharmacologic medications and natural supplements to reduce intraocular pressure and preserve optic nerve function.
Lab Tests in This Article
1. Don't Let Glaucoma Steal Your Sight! (2020, November 24). Centers for Disease Control and Prevention. https://www.cdc.gov/visionhealth/resources/features/glaucoma-awareness.html
2. Dietze, J., Blair, K., & Havens, S.J. (2022). Glaucoma. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK538217/
3. NIH. (2021, September 10). Types of Glaucoma. National Eye Institute. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/glaucoma/types-glaucoma
4. Glaucoma: Symptoms, Causes, Types & Treatment. (2022, November 18). Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/4212-glaucoma
5. What Is Glaucoma? Symptoms, Causes, Diagnosis, Treatment. (2023, January 19). American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/what-is-glaucoma
6. Glaucoma - Symptoms and causes. (2022, September 30). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/glaucoma/symptoms-causes/syc-20372839
7. Huang, W., Fan, Q., Wang, W., et al. (2013). Collagen: A potential factor involved in the pathogenesis of glaucoma. Medical Science Monitor Basic Research, 19, 237–240. https://doi.org/10.12659/msmbr.889061
8. Gupta, D., & Chen, P. P. (2016). Glaucoma. American Family Physician, 93(8), 668–674. https://www.aafp.org/pubs/afp/issues/2016/0415/p668.html
9. Erickson, K. (2022, July 21). The Benefits of Therapy for Mental Health. Fullscript. https://fullscript.com/blog/benefits-of-ginkgo-biloba
10. Park, J.C., Kwon, H.U., Chung, W.C., et al. Short-Term Effects of Ginkgo biloba Extract on Peripapillary Retinal Blood Flow in Normal Tension Glaucoma. Korean Journal of Ophthalmology, 25(5), 323. https://doi.org/10.3341/kjo.2011.25.5.323
11. Cybulska-Heinrich, A., Mozaffarieh, M., & Flammer, J. (2012). Ginkgo biloba: an adjuvant therapy for progressive normal and high tension glaucoma. Molecular Vision.
12. Giblin, F.J. (2000). Glutathione: A Vital Lens Antioxidant. Journal of Ocular Pharmacology and Therapeutics, 16(2), 121–135. https://doi.org/10.1089/jop.2000.16.121
13. Ganea, E., & Harding, J.C.S. (2006). Glutathione-Related Enzymes and the Eye. Current Eye Research, 31(1), 1–11. https://doi.org/10.1080/02713680500477347