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A Complete Guide to Glaucoma

Posted on January 11th, 2022

January is National Glaucoma Awareness month, and we’re sharing all the information you need to know about the eye disease, plus steps you can take to prevent and treat it. 

Glaucoma affects roughly 400,000 Canadians and 67 million people worldwide, and is one of the leading causes of blindness. Educating yourself about glaucoma and understanding the many risks associated with it is an important step to help protect and preserve your eye health. 

What is glaucoma?

Simply put, Glaucoma is a group of eye diseases that progressively degenerate the optic nerve, leading to loss of nerve tissue and potential blindness. The cause of these diseases is not entirely known, though some theories point to inadequate blood supply or poor perfusion, which is the passage of fluid through the circulatory system. 

Typically, glaucoma arises when the eye is no longer draining fluid properly. This is due to an inefficient draining system, resulting in fluid buildup and increased intraocular pressure (IOP) in the eyes. 

The pressure damages the eye’s optic nerve function, which can result in visual field loss. The vision loss will usually first appear in the peripheral vision, a warning sign that glaucoma may be present or on the horizon. The good news is, routine eye exams can usually determine if glaucoma is present long before any vision loss is noticed by the patient. 

Four types of glaucoma

There are several forms of glaucoma, including the following four, which are the most common types you should know about:  

  1. Primary open-angle glaucoma: The most common form of glaucoma, primary open-angle glaucoma is when pressure is placed on the optic nerve. Aqueous fluid is produced inside the walls of the eye, but if too much of it is being produced within the eye or is not draining properly, it can create unwanted pressure. One theory behind why this happens is that when the eye’s drainage system becomes inefficient over time, the capillaries in your optic nerve become damaged, which in turn damages the optic nerve as a whole and decreases the amount and quality of information sent to the brain. This results in a loss of vision. Peripheral vision is affected first, followed by central.

  2. Angle-closure glaucoma: Also known as closed-angle or narrow-angle glaucoma, angle-closure glaucoma is a faster moving ailment that can cause vision loss within one day. Angle-closure glaucoma is caused when the drainage angle in the eye formed by the cornea and the iris closes or becomes completely blocked. With age, the lens in your eye enlarges, pushing the iris forward and narrowing the space between the iris and the cornea. The aqueous fluid is then prevented from exiting your eye’s drainage system, creating the buildup of eye pressure and fluid. Angle-closure glaucoma can be chronic or acute.

  3. Secondary glaucoma: This type of glaucoma can occur as the result of an injury, eye surgery, infection, or tumour growth in or around the eye, causing pressure to rise. It has also been linked to a variety of medical conditions, medications, and eye abnormalities.

  4. Normal-tension glaucoma: In this form, eye pressure stays within the normal range, but the optic nerve is still damaged.

Risk factors 

While glaucoma can happen to anyone, the Mayo Clinic outlines some key risk factors that can contribute to the diagnosis, including:

  • being over 60 years old

  • a family history of glaucoma

  • medical conditions, such as diabetes, heart disease, high blood pressure, or sickle cell anemia

  • corneas that are thin in the centre

  • eye injuries

  • being extremely nearsighted or farsighted

  • taking corticosteroid medications (like eye drops) for a prolonged period

Having any of these factors certainly does not mean you are guaranteed to develop glaucoma, but it’s always a good idea to be aware of your medical history and risk factors, and let your optometrist know if you have any questions or concerns. As we mentioned above, scheduling yearly eye exams is an excellent preventative measure to ensure your eyes are being monitored for the first signs of disease.

Diagnosing glaucoma

Optometrists have many tools when it comes to testing and diagnosing a patient with glaucoma. Depending on the specific case, they may use scanning, eye drops or simple diagnostic measures to determine if someone is suffering from the disease. The most common diagnostic tools include: 

  • Ophthalmoscopy: Eye drops are used to dilate the pupil. The doctor is then able to examine the optic nerve more clearly to determine if there is damage.

  • Retinal Imaging: Similar to ophthalmoscopy, the goal is to view the optic nerve. In this case, laser scanning is utilized to form a fuller picture of the back of the eye. At FYidoctors, we use the Optomap Retinal Scanner during eye exams, for comprehensive digital imaging.

  • Tonometry: This is a pressure test of the eye. Drops are used to numb the eye and a tool is carefully placed on the outside of the eye, which gives a pressure reading. Average pressure is 16 mm Hg, and although anything higher is not necessarily an indication of glaucoma, it is a possible sign, which optometrists will analyze. Non-contact tonometry (an air puff test) is also an option.

  • Perimetry: A computerized visual field test in which the patient stares straight ahead and must identify lights that appear in their periphery.

  • Gonioscopy: This test directly looks at the drainage system of the eye. Doctors will numb the eye and place a special lens on the exterior to examine the frontal area closely.

  • Optical Coherence Tomography (OCT): A special type of imaging of the optic nerve and macula. OCT gives doctors precise information about potential damage to the nerve fibre layer of the retina that concerns glaucoma.

You may recognize some of these tests, as optometrists conduct similar exams during regular eye check-ups. 

How to treat glaucoma 

Once a doctor diagnoses a patient with glaucoma, the next step is looking at treatment options. Treatment typically is offered in one of two ways—medication or surgery. Although there is no cure for glaucoma, treatment and prevention protocols do exist to prevent further damage and vision loss. 

According to the Glaucoma Research Society of Canada, “the primary effect of most glaucoma medications is lowering Intra-Ocular Pressure (IOP). This has been proven over the years to be an effective way to prevent or slow down the progression of the disease.” 

Medications that lower IOP are a positive development in limiting the effects of glaucoma, and some common treatment protocols include:

  • Beta Blockers: The most common beta blocker used is timolol. These drugs reduce production of aqueous humor (fluid in the eye), which will lower pressure.

  • Alpha Agonists: Those who use alpha agonists will apply it to the eye to decrease aqueous humor productions and increase the outflow of liquid from the eye. Both activities lower IOP. An example of an alpha agonist is brimonidine.

  • Carbonic Anhydrase Inhibitors: Common CAIs are brinzolamide or dorzolamide. They are applied to the eye and will also decrease the production of aqueous humor.

  • Miotics: A common miotic is pilocarpine. This particular medication increases outflow of liquid and decreases IOP.

If medication is unsuccessful, doctors may recommend that a patient should consider having surgery. Glaucoma patients can either have laser surgery or filtering microsurgery. Laser treatment is conducted with a light beam, which makes multiple scars on the eye’s draining system, increasing the outflow of fluid in the eye. 

In the case when laser surgery does not work, filtering microsurgery may be recommended. This is slightly more invasive—a drainage hole is created with a surgical tool to drain liquid. Your optometrist will know best which option to take in your unique case.

New glaucoma treatments 

Diagnostics and treatment are evolving all the time. As research continues and scientists better understand glaucoma, more options for patients are coming to light. Glaucoma Today, a publication that explores new advancements in glaucoma care, has published several studies on new and promising diagnostic endeavours.

A 2019  study explores anterior segment OCT, otherwise known as AS-OCT. This precision angle imaging device offers an alternative to gonioscopy; it doesn’t require any contact with the eye and can be done in darkness under standard lighting conditions. 

Teleophthalmology, or telemedicine, is the ability to conduct tests in the patient’s home without having to go to a doctor’s office, which is an especially useful tool amid the COVID-19 pandemic. 

In Glaucoma Today’s 2019 article, portable IOP-monitoring devices are discussed, including the Icare tonometer (Icare USA), which allows for at-home pressure readings that can be shared with a provider remotely. This type of diagnostic tool could limit the time a patient spends in the doctor’s office and potentially help save health care resources.

In conclusion 

Glaucoma can be confusing to navigate, which is why it’s always best to talk to your optometrist about treatment options. Scheduling yearly eye exams can help prevent glaucoma by detecting the disease at an early stage and stopping it in its tracks. Visit an FYidoctors clinic near you today to book your next appointment.