Glaucoma

Overview

Glaucoma is the second leading cause of blindness in North America, affecting more than 400,000 Canadians, and takes the form of a number of related disease-types. The most common types are open-angle, which is more prevalent and can go unnoticed due to a lack of early symptoms, and angle-closure, which can be painful with a sudden onset—in both cases the eye’s drainage canals are blocked, leading to a build-up of aqueous humor fluid and increased intraocular pressure (IOP) that damages the optic nerve. The cellular interactions that make sight possible occur within the retina, which is composed of light-sensitive tissue, but it is the optic nerve that sends the retina’s visual information to the brain. There is no cure for glaucoma, but early detection and treatment can help prevent damage to the optic nerve and, as a result, save vision.

Anyone can develop glaucoma; that said, there are several different factors that can increase your risk of developing the disease, including: high intraocular pressure (fluid pressure inside the eye); high blood pressure; a family history of glaucoma; corneal thickness, which affects eye pressure readings; being over the age of 40; previous eye injuries; long-term use of steroids; African, Asian, or Hispanic ancestry; nearsightedness; and diabetes.

Optic Nerve Picture

 

 

 

 

 

 

Image highlighting the optic nerve from the American Academy of Ophthalmology
https://www.aao.org/eye-health/anatomy/optic-nerve-3

Symptoms and Detection

Glaucoma can develop in one or both eyes, and in most forms of the disease there are no early symptoms that can be self-detected. It is essential to have regular eye exams so that your doctor can conduct the appropriate tests that will detect glaucoma and save your vision. If you experience any of these symptoms, please visit your ophthalmologist:

  • – Loss of peripheral (side) vision
  • – Halos around lights
  • – Eye pain and/or redness
  • – Blurred or decreased vision
  • – Eye pain

Your ophthalmologist is able to conduct a number of different tests and offer a more specific diagnosis, including: visual acuity tests to assess your ability to see from different distances; visual field tests to measure your peripheral vision; dilated eye exams; ocular tonometry to measure the intraocular pressure inside your eye; pachymetry to measure corneal thickness; and optical coherence tomography (OCT) to scan the retina and optic nerve.

Treatment

Currently there is no cure for glaucoma, but there are treatment options that are designed to lower the build-up of fluid in the eye that can lead to optic nerve damage. Some of the main categories of treatment-types are below; their appropriateness depends on the type and stage of the disease. As always, be sure to discuss treatment options with your ophthalmologist.

  • – Drug therapy: Eye drops and pills are the most common early treatment for glaucoma, and are capable of lowering eye pressure when taken regularly. Beta-blockers are used to decrease the amount of fluid in the eye; prostaglandin analogues and prostamides are used to increase the outflow of fluid from the eye; and alpha-agonists and carbonic anhydrase inhibitors (CAIs) are both used to decrease the eye’s production of fluid. When prescribed, the regular use of these medicines is very important.

– Laser surgery: Various forms of laser surgery have been shown to have beneficial effects, and can often function as a middle ground between drug therapy and MIGS (least invasive, see below for MIGS) and conventional surgery (most invasive). Trabeculoplasty is the most common procedure, characterized by the use of a laser to open the trabecular meshwork of the eye, located at the base of the cornea, in order to improve drainage. Other approaches create openings in the iris, or remove parts of the ciliary body, which is responsible for producing fluid.

– Conventional surgery: As with trabeculoplasty, more conventional surgical techniques—usually categorized as trabeculectomy—can be used to create new openings for fluid to leave the eye. A drainage hole or “flap” is created to facilitate the expulsion of fluid from the eye through the space between the sclera (the outer, protective layer of the eye) and the conjunctiva, the thin membrane that sits on top of the sclera. Since these techniques can lead to more severe side-effects, including worsened vision, they are typically a last resort in the event that less invasive approaches are ineffective.

– Minimally invasive glaucoma surgery (MIGS): MIGS names a group of devices and operations that have been developed in recent years to reduce some of the complications that can result from the existing range of techniques. As with more established approaches, the goal of these surgeries is to either increase the outflow of fluid from the eye or reduce the production of that fluid. What distinguishes MIGS, however, is the use of small cuts or micro-incisions, usually through the cornea, that minimize trauma to the surrounding eye and decrease the chances of side-effects, leading in many cases to more rapid recovery. In Canada, MIGS approaches are only covered by provincial health insurance programs in Alberta and Quebec, but surgeons in other jurisdictions are beginning to use MIGS as a replacement for other approaches. The subject of MIGS’s implementation is currently being reviewed by the CADTH, the Canadian Association for Drugs and Technologies in Health (see below).

Developments

    • – MIGS and CADTH: In March of 2018, the Canadian Association for Drugs and Technologies in Health (CADTH) began an environmental scan of MIGS in Canada. The scan is designed to collect relevant information on MIGS practices and offer conclusions that will factor into future policy decisions, including whether or not the surgeries will be publicly insured. In an effort to guide CADTH’s analysis of MIGS along patient-centered lines, the Foundation Fighting Blindness submitted patient group feedback in collaboration with the Canadian Council of the Blind (CCB) and Canadian National Institute of the Blind (CNIB), taking the form of three frameworks to steer the study and the overall question of implementation. You can access the submission in both Word and PDF formats through the following links: click here for the submission in Word; click here for the submission in PDF.
    • – Optic nerve regeneration: Though still in the early stages of experimentation and development, work is being done to develop an approach to reversing optic nerve damage caused by glaucoma. Usually taking the form of cell-based interventions—using cells to regenerate tissue, including stem cells—or in blocking molecules that inhibit degeneration, there have been clinical trials to test the efficacy of these approaches and research continues to move forward. The Foundation Fighting Blindness will continue to monitor progress in this area.