January is National Glaucoma Awareness month. In honour of this important month, we are going to share key information about this disease and the steps you can take to prevent and treat it. Glaucoma affects 400,000 Canadians and 67 million people worldwide. It is one of the leading causes of blindness, which is why it’s important to know its causes and how doctors can diagnose for the disease.
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 eyes. The pressure damages the eye’s optic nerve function, which can cause visual field loss. The vision loss will usually first appear in peripheral vision, a warning sign that glaucoma may be present. Routine testing can usually determine if glaucoma is present long before this loss of peripheral vision is noticed by the patient.
While glaucoma can happen to anyone, the Mayo Clinic outlines some risk factors that could contribute to the diagnosis. For example, being over 60 years old could increase your likelihood of developing the disease. Other factors can be a family history of glaucoma, or having medical conditions like diabetes, heart disease, high blood pressure or sickle cell anemia. Corneas that are thin in the centre may be a risk factor as well as having an eye injury, being extremely nearsighted or farsighted, or taking corticosteroid medications (like eyedrops) for a prolonged period. Having any of these factors doesn’t mean you will develop glaucoma, but it’s always a good idea to be aware of them and let your optometrist know. Having regular eye exams is an excellent preventative measure to ensure your eyes are being monitored for symptoms.
Optometrists have many tools for how to test for glaucoma in a patient. Depending on the specific case, they may use scanning, eye drops or simple diagnostic measures to determine if someone is suffering from the disease. Below is a list of the most common diagnostics used by eye doctors:
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. The instrument gives a pressure reading. Average pressure is 16 mm Hg, anything higher is not necessarily an indication of glaucoma, but 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 in their regular eye checkups for preventative measures. 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.
The Glaucoma Research Society of Canada states: “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 is a positive development in limiting the effects of glaucoma. Here are a few common eye drop medications used to treat glaucoma:
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 production 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 a patient have 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.
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 diagnostic endeavours.
One new study explores anterior segment OCT, or 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. Glaucoma today suggests “AS-OCT can be a valuable tool for the identification and sequential evaluation of patients [...] it is especially advantageous for evaluating degrees of narrow angles and angle closure.”
Telephthalmology or telemedicine, is the ability to conduct tests in the patient’s home without having to go to a doctor’s office. In Glaucoma Today’s 2019 article, they introduce “Portable IOP-monitoring devices such as the Icare tonometer (Icare USA) [which] offer 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 save health care resources.
What’s clear is glaucoma is a complicated disease with many facets of diagnostics and treatment. It is best to talk to your optometrist about treatment options and receive regular eye exams to help prevent glaucoma and potentially detect the disease in early stages. Visit an FYidoctors clinic near you today to book your next appointment.