What is Glaucoma?

Glaucoma is a group of eye diseases which results in damage to the optic nerve due to high intraocular pressure (IOP) of the eye from fluid build-up. Glaucoma is the second leading cause of vision loss.

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What is Glaucoma?

Glaucoma is a group of eye diseases that can cause vision loss and blindness by damaging a nerve in the back of your eye called the optic nerve.  The damage to the optic nerve is caused by increased pressure when fluid builds up as a result of improper drainage or overproduction of fluid. Glaucoma can lead to vision loss if not treated. Vision loss from glaucoma, once it has occurred, is permanent. According to the American Academy of Ophthalmology, glaucoma is the leading cause of blindness in adults aged 60 and older.

Types of Glaucoma

There are several types of glaucoma. The most prevalent type of glaucoma is open-angle glaucoma, or OAG, with less common types including closed-angle glaucoma, or CAG, and normal-tension glaucoma. Open-angle glaucoma accounts for about 85% of all glaucoma cases.

Open-angle glaucoma

Open-angle glaucoma occurs where there is a limited release of fluid through the trabecular meshwork. The undrained fluid increases the eye pressure, known as intraocular pressure or IOP.  In OAG, the angle at which the iris meets the cornea is open, but the drainage through the trabecular meshwork is partially blocked. Damage to the neurons from open-angle glaucoma is very gradual and most people will not notice symptoms until substantial damage has occurred. If left untreated, side vision may begin to decrease followed by central vision (see picture to the right on an example of loss of side vision). Diagnosis is typically made by a dilated eye examination.

Closed-angle glaucoma

Closed-angle glaucoma, or CAG, also referred to as angle-closure glaucoma, is often a result of a damaged iris. It occurs when the drainage angle between the cornea and iris is blocked or narrowed and the fluid is unable to drain, resulting in fluid build-up and pressure in the eye. CAG can develop gradually or suddenly and involve severe eye pain, blurred vision, mid-dilated pupil, redness of the eye and nausea.

Learn more about the different types of glaucoma at the National Institutes of Health (NIH) National Eye Institute.

An example of the effect of glaucoma on field of vision
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What causes Glaucoma

Glaucoma occurs when fluid build-up increases the pressure in the eye resulting in damage to the optic nerve.

Your eyes are constantly producing fluid, known as aqueous humor, to keep your eyes moist and healthy. As new fluid is produced, the same amount should drain out – maintaining a balance of production and outward flow of fluid. When an imbalance occurs from either overproduction or improper drainage of the fluid, pressure within the eye increases. This pressure, known as intraocular pressure or IOP, damages the optic nerve and leads to glaucoma.

Glaucoma risk factors

While glaucoma can affect anyone, certain people are at higher risk. According to the U.S. National Eye Institute, increased risk factors for glaucoma include:
• diabetes or hypertension
• a previous eye injury
• a family history of the condition
• African American age 40 and older
• anyone 60 years of age and older (especially Hispanics/Latinos)
• High eye pressure (those with a value of greater than 21 mmHg or 2.8 kPa)

Glaucoma symptoms

Quite often, glaucoma symptoms don’t appear until vision loss starts to occur. Open-angle glaucoma develops slowly over time and there is no pain. Individuals with open-angle glaucoma often notice peripheral vision loss first and have trouble seeing from the sides of their eyes. This can lead to central vision loss and blindness. Once vision loss from glaucoma has occurred, it is permanent.

When detected early, by a dilated eye exam, glaucoma can be prevented or progression can be slowed down through treatment. Anyone with risk factors related to glaucoma can monitor their eye health through regular eye exams and mitigate the onset or progress of the disease through treatment if needed.

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Glaucoma Quick Facts
  • Glaucoma is the second leading cause of blindness worldwide
  • Glaucoma is the leading cause of blindness in people age 60+
  • Glaucoma affects about 3.5% of the population, aged 40-60
  • It’s estimated 76M people worldwide have glaucoma
  • Open-angle glaucoma accounts for about 85% of glaucoma diagnoses
  • An estimated 3.5 million North Americans live with open-angle glaucoma
  • Men are more likely to have open-angle glaucoma than women

Current Glaucoma Treatments

Current treatments for glaucoma include medication, laser treatment and surgery. The goals of glaucoma management are to avoid glaucomatous and nerve damage, and preserve visual field and quality of life for patients, with minimal side effects. Although intraocular pressure (IOP) is only one of the major risk factors for glaucoma, lowering it via various pharmaceuticals and/or surgical techniques is currently the mainstay of glaucoma treatment.

If treated early, it is possible to slow or stop the progression of the disease with medication, laser treatment, or surgery. The goal of these treatments is to decrease eye pressure. Currently, several different classes of glaucoma medication are available. Laser treatments may be effective in both OAG and CAG. A number of types of glaucoma surgeries may be used in people who do not respond sufficiently to other measures. Treatment of CAG is a medical emergency.

Current prescription eyedrop medications include:

  • Prostaglandins such as latanoprost, bimatoprost and travoprost to increase the outflow of fluid from the eye and reduce ocular pressure. These can sting the eyes, darken the iris and eyelashes, and blur vision.
  • Beta blockers such as timolol and betaxolol reduce ocular pressure by reducing the production of fluid in the eye. Possible side effects include wheezing or difficulty breathing, slowed heart rate, lower blood pressure, impotence and fatigue.
  • Alpha-adrenergic agonists such as apraclonidine and brimonidine, both reduce the production of aqueous humor and increase the outflow of fluid from the eye. Side effects may include dry mouth, red eyes or eyelids, fatigue, low or high blood pressure, blurred vision and light sensitivity.
  • Carbonic anhydrase inhibitors such as dorzolamide and brinzolamide also reduce the production of fluid in the eye, but they are associated with blurred vision, bitter metallic taste in the mouth, dry eyes, red/irritated eyes, headache, and upset stomach.

Often patients need to take multiple eye drops throughout the day. Given the side effect profiles, many patients don’t take their medications properly or at all.

Surgery and laser therapies are intended to physically improve the drainage of fluid from the eyes, lowering pressure. Patients with OAG can have clogged channels in the trabecular network opened with laser therapy, filtering surgery (trabeculectomy) or electrocautery. In other cases, small drainage tubes may be implanted in the eye. Possible complications include pain, redness, infection, inflammation, bleeding, abnormally high or low eye pressure and loss of vision. Some types of eye surgery may increase the development of cataracts. Additional procedures may be needed if eye pressure continues to increase.

Glaucoma resources
Selected publications
Cannabinoids a promising treatment option for glaucoma

The use of cannabis to treat glaucoma has extensive anecdotal evidence and supporting clinical data. It has been definitively demonstrated in articles that smoking cannabis lowers intraocular pressure (IOP) in both normal individuals and those with glaucoma.

Learn more about the history of cannabis and glaucoma.

InMed is developing a cannabinoid formulation for glaucoma

INM-088 is a topical, single cannabinoid formulation under development for the treatment of glaucoma. The active pharmaceutical ingredient (API) in INM-088 is cannabinol, also known as CBN, a rare cannabinoid showing promise in its potential to provide neuroprotection and reduce intraocular pressure of the eye.

InMed is developing INM-088 to provide a dual mechanism of action:

  • Reduce the intraocular pressure (IOP) in the affected eyes
  • Provide neuroprotection for the retinal ganglion cells (RGCs) and other optic nerve tissues in the affected eyes.