Glaucoma

Glaucoma is a group of eye diseases that cause abnormally high intraocular pressure (IOP) and/or fluid buildup in one or both eyes, damaging the optic nerve and potentially impairing vision. Approximately 3 million Americans suffer from Glaucoma, and it is the second leading cause of blindness worldwide.

There are several medications that have been developed to manage pain and pressure associated with glaucoma, but medical cannabis can be useful as an adjunctive or alternative therapy.

Glaucoma causes

Glaucoma is typically the result of an injury to the optic nerve, although it can develop in eyes with otherwise normal IOP. Glaucoma without an increase in IOP is called “normal tension glaucoma.”

Common causes of secondary glaucoma (glaucoma arising as a result of another condition) include diabetes, uveitis, or pigment dispersion syndrome. Depression, anxiety, and insomnia are also associated with an increased risk of glaucoma.

Age, family history, and some conditions and medications can increase the likelihood of glaucoma. Black, Asian, and Latino ethnic groups, and those above the age of 40 are more likely to be glaucoma patients.

Glaucoma symptoms & health effects

For around half of people with glaucoma, there are few if any early symptoms of glaucoma in the early stages of the condition. Typical symptoms include blurred vision, blind spots in one’s peripheral vision, and seeing rainbow-colored circles around bright lights.

Glaucoma diagnosis

Glaucoma is usually picked up during an eye test by an optician, who will refer to a specialist eye doctor (ophthalmologist). An ophthalmologist will then determine the type of glaucoma by carrying out one of more of the following tests:

• Eye pressure test (tonometry): An instrument called a tonometer is used to measure the pressure inside your eye

• Air puff test: An alternative test used to measure eye pressure

• Gonioscopy: An assessment designed to inspect the anterior segment of the eye that involves examining the fluid-filled space located between the colored portion (iris) and the transparent surface at the front of the eye (cornea). This region is crucial for the proper drainage of fluid from the eye.
  Gonioscopy serves to determine whether this area, referred to as the “angle,” is either open or obstructed, which can influence the drainage of fluid. The results of this examination will provide your optometrist with information regarding the specific type of glaucoma you may have.

• Visual field test: A visual field test (perimetry) checks for missing areas of vision, typically using spots of light. The first area of the vision to be affected is usually peripheral vision (the edges of your vision).
• Optic nerve assessment: Checks to see if the optic nerve is damaged, typically by using a slit lamp (a microscope with a bright lamp) and/or a type of medical imaging called “optical coherence tomography.” This is a type of exam where rays of light are used to scan the back of your eye and produce an image of the optic nerve.

These tests will determine whether you have one of the following types of glaucoma::

• Open-angle glaucoma
• Angle-closure glaucoma, also called closed-angle glaucoma
• Congenital glaucoma
• Normal tension glaucoma (glaucoma without intraocular pressure but other symptoms typical of glaucoma, such as blurred vision, or rainbow/halo vision)
• Secondary glaucoma

Glaucoma prognosis

Glaucoma is not a life-threatening condition, and the life expectancy of someone with glaucoma is similar to that of the general population.

However, glaucoma can cause significant impact on one’s quality of life (QoL), and leads to blindness if not treated in time.

Glaucoma treatments

Treatment of glaucoma depends on the symptoms, but typically includes prescription medications, laser treatment, or surgery.

First-line treatments

Regular eye exams, adherence to medication regimens, and lifestyle modifications can help preserve vision and overall health, reducing the risk of glaucoma from developing in the first place.

Usually, specialized eye drops will be prescribed as a first-line treatment. These eye drops lower IOP.

Types of eye drops include:

• Prostaglandins: Xalatan (latanoprost), Travatan Z (travoprost), Zioptan (tafluprost) and Lumigan (bimatoprost)
• Rho-kinase inhibitors: Rhopressa (netarsudil)
• Nitric oxides: Vyzulta (latanoprostene bunod)
• Miotic or cholinergic agents: Isopto Carpine (pilocarpine)

Other treatments

If first-line prescription medications do not work, then one of the following types of eye drops may be prescribed. These lower the amount of fluid in the eye.

• Alpha-adrenergic agonists: Iopidine (apraclonidine) and Alphagan P or Qoliana (brimonidine)
• Beta blockers: Betoptic (betaxolol) and Betimol, Istalol, or Timoptic (timolol)
• Carbonic anhydrase inhibitors: Trusopt (dorzolamide) and Azopt (brinzolamide)

Laser eye treatment and/or surgery may also be required in some instances.

Adjunctive therapy & alternative treatments

Although there are many effective treatments for glaucoma nowadays, there are many adjunctive treatments that can help manage symptoms like pain and eye pressure. This is because of their antioxidative effects, which reduce cell damage caused by oxidation and free radicals.

• Ginkgo Biloba, which has antioxidant, bronchodilatory, and anti-inflammatory properties that may help reduce pain, stress, and eye pressure associated with glaucoma
• Consumption of dark, leafy greens such as spinach and kale, due to their levels of vitamin A, C, K, and nitrate
• Omega-3 supplementation to reduce inflammation and protect from oxidative stress
• Melatonin, which can help manage insomnia associated with glaucoma
• Turmeric/curcumin, which can help reduce inflammation
• Green tea for its antioxidant effects

Cannabis for glaucoma

In the 1970s, there were few medications available for glaucoma that didn’t have some serious side effects. Moreover, glaucoma was — and still is — the second most common cause of blindness worldwide, after cataracts. The condition can be challenging to treat, so researchers experimented with cannabis as an alternative.

Researchers found that various cannabinoids, particularly THC and CBG, may lower intraocular eye pressure. Terpenes like myrcene, linalool, and beta-caryophyllene can help aid relaxation and reduce stress, while certain flavonoids in cannabis like Cannflavins A, B and C, kaempferol, and luteolin may have anti-glaucoma effects.

Cannabis’ potential neuroprotective and antioxidant effects could help reduce the risk of retinal toxicity (damage to the retina that can cause vision loss), though several newer glaucoma medications may provide longer-term pain and pressure relief by comparison.

However, for those who cannot tolerate current glaucoma medications, medical cannabis may be a useful alternative. Drugs such as Latanoprost/Xalatan and Timolol/Timoptic are arguably more effective compared to cannabis, but aren’t without their problems. Side effects of these medications include joint/muscle pain, flu-like symptoms, blurred vision, depression, and impotence, which may be difficult to tolerate for some patients.

Medical cannabis may also be useful for those whose glaucoma is a result of diabetes or nerve pain (neuropathy). Medical cannabis may also help manage headaches/migraines, anxiety, depression, and insomnia, which can trigger or result from glaucoma symptoms.

Those who intend to use medical cannabis for glaucoma should avoid smoking it, as smoke may irritate the eyes. Overconsumption of THC through inhalation may also increase heart rate in the short-term, which can increase pressure. A vaporizer is ideal if immediate relief is needed, as are tinctures for long-term relief without any smoke.

Additional information for patients

Glaucoma is a common cause of blindness, and as such there are many resources available that can help. Some include:

• American Glaucoma Society
• BrightFocus Foundation
• The Glaucoma Foundation
• Glaucoma Research Foundation

Glaucoma FAQs

How high is too high for intraocular pressure (IOP) and glaucoma?

The threshold for “too high” IOP varies depending on the individual and the stage of the condition. Generally, IOP above 21 mm Hg is considered elevated, and treatment may be necessary to prevent further optic nerve damage and vision loss.

Which cannabinoid is good for glaucoma?

Currently, THC is thought to be the most effective cannabinoid for lowering IOP and managing glaucoma symptoms. Some reports suggest that CBD may increase

IOP in some people, but more research is needed to determine the impact of other cannabinoids on glaucoma treatment. CBD has some potential benefits, such as anti-inflammatory and antioxidant effects that may help manage some types of glaucoma when combined with THC.

How long does it take to go blind or lose significant vision from glaucoma?

It can take an average of 10-15 years for glaucoma to cause significant vision loss or blindness.

Can you drive with glaucoma?

If caught and treated early enough, it is possible to drive with glaucoma. However, for those with more advanced glaucoma and significant damage to one or both eyes, driving may not be possible.

Resources

• About Glaucoma: https://www.cdc.gov/vision-health/about-eye-disorders/glaucoma.html
• The Impact of Anxiety and Depression to Glaucoma Among Glaucoma Suspects: https://pmc.ncbi.nlm.nih.gov/articles/PMC9924953/
• Racial and Ethnic Disparities in Adherence to Glaucoma Follow-up Visits in a County Hospital Population: https://jamanetwork.com/journals/jamaophthalmology/fullarticle/1106359
• Common Drugs That Can Worsen Glaucoma: https://www.aao.org/eye-health/tips-prevention/dangerous-medications-glaucoma-dayquil-bendadryl
• Ocular beta-blockers in glaucoma management. Clinical pharmacological aspects: https://pubmed.ncbi.nlm.nih.gov/1351412/
• Gingko biloba: An adjuvant therapy for progressive normal and high tension glaucoma: https://pmc.ncbi.nlm.nih.gov/articles/PMC3283204/
• Alternative therapy in glaucoma management: Is there any role?: https://pmc.ncbi.nlm.nih.gov/articles/PMC3038502/
• Melatonin, circadian rhythms, and glaucoma: current perspective: https://pmc.ncbi.nlm.nih.gov/articles/PMC8820707/
• Green tea – a new perspective on glaucoma prevention: https://pmc.ncbi.nlm.nih.gov/articles/PMC9091885/
• Treatment of Glaucoma with Natural Products and Their Mechanism of Action: An Update: https://pmc.ncbi.nlm.nih.gov/articles/PMC8840399/
• Cannabinoids and glaucoma: https://pmc.ncbi.nlm.nih.gov/articles/PMC1772142/
• Neuroprotective effect of (-)Delta9-tetrahydrocannabinol and cannabidiol in N-methyl-D-aspartate-induced retinal neurotoxicity: involvement of peroxynitrite: https://pubmed.ncbi.nlm.nih.gov/14578199/
• Review of the neurological benefits of phytocannabinoids: https://pmc.ncbi.nlm.nih.gov/articles/PMC5938896/

The effect of flavonoids on visual function in patients with glaucoma or ocular hypertension: a systematic review and meta-analysis: https://pubmed.ncbi.nlm.nih.gov/26340868/

Note that the information in this article does not constitute medical advice.