Glaucoma refers to a group of diseases that damage the optic nerve, which can lead to vision loss. If it remains untreated, glaucoma progresses gradually from blind spots in the peripheral vision initially, to tunnel vision later on, and finally to total blindness. In Canada, one in a hundred individuals over the age of 40 is affected.
What is glaucoma? Glaucoma refers to a group of diseases that damage the optic nerve, which can lead to vision loss. The optic nerve is a cable of over a million fibres that transmit visual information perceived by the eyes to the brain. If it remains untreated, glaucoma progresses gradually from blind spots in the peripheral vision initially, to tunnel vision later on, and finally to total blindness. In Canada, one in a hundred individuals over the age of 40 is affected.
Why should I be concerned?
Glaucoma is the second leading cause of blindness. Sometimes called the “sneak thief of sight,” glaucoma can damage vision so gradually that persons affected only notice the loss of visual acuity once the disease is at a very advanced stage.
Who is at risk?
Everyone is at risk of developing glaucoma, although some people are at a higher risk:
- Intraocular pressure: persons with elevated intraocular pressure (IOP) are at a higher risk for glaucoma. However, an elevated IOP does not necessarily lead to glaucoma.
- Age: individuals over the age of 60.
- Genetics: a family history of glaucoma.
- Ethnic background: persons of African descent are six to eight times more likely to develop glaucoma than Caucasians. Mexicans and Asians are also at a higher risk.
- Other diseases: diabetes is known to increase the risk of suffering from glaucoma, as is hypertension and certain heart problems.
Are all cases of glaucoma the same?
There are several types of glaucoma. The most common are primary open-angle glaucoma and acute closed-angle glaucoma. These two types of glaucoma can appear suddenly and without warning, or can have a readily identifiable cause such as an injury, inflammation, tumour, severe cataract or diabetes. Glaucoma can affect one or both eyes.
How does glaucoma appear?
The anterior chamber, an area in the front of the eye, contains a clear liquid called the aqueous humour, which circulates in order to nourish the surrounding tissue. This fluid exits the chamber through drainage canals located in the angle where the cornea meets the iris.
In primary open-angle glaucoma, the drainage angle formed between the cornea and the iris remains open, but the drainage canals are partially blocked, which means the aqueous humour is not drained quickly enough. In the long run, this overly slow drainage increases the IOP, which can eventually damage the optic nerve.
The problem with open-angle glaucoma is that the optic nerve damage does not cause any pain and occurs so slowly that a significant amount of vision can be lost before the person even realizes it. It is therefore very important to get regular eye exams.
Closed-angle glaucoma, on the other hand, usually appears abruptly, when the iris suddenly blocks the drainage angle formed between the cornea and iris. Since the aqueous humour can no longer drain out of the eye, the IOP quickly increases and causes characteristic symptoms: significant eye pain, nausea and vomiting, blurred vision, halos around lights, sudden visual disturbances. This type of glaucoma is considered a medical emergency.
What can I do to avoid glaucoma?
Early diagnosis and treatment can minimize or prevent optic nerve damage and limit glaucoma-related vision loss. A routine eye exam is recommended every two years in adults under the age of 60, and every year in those over 60. Individuals in whom the risk is greater, including persons of African descent, could benefit from more frequent exams. During these exams, an optometrist or ophthalmologist uses various instruments to measure IOP, visual acuity and the state of various eye structures, such as the optic nerve.
Is it treatable?
The treatment for glaucoma aims to reduce the production of aqueous humour, to facilitate its flow, or both. There is no cure for glaucoma and once lesions have occurred, they cannot be reversed. Regular treatment and monitoring, however, can prevent vision loss if the disease is detected early. If vision loss has already occurred, proper treatment can slow or prevent further damage.
Glaucoma treatment often begins with the daily administration of eye drops. There are several types of drops, and they are used in different ways. Make sure to use the drops as prescribed by your physician, otherwise they may be less effective. Having your pharmacist regularly check your eye drop application technique may help increase the efficacy of these products, while also reducing the risk of adverse effects stemming from them.
For individuals in whom drops are not sufficient, medication taken orally or certain surgical procedures may be considered.
Early detection and treatment of glaucoma are the best ways to prevent vision loss, so make sure to visit your eyecare professional on a regular basis. If you have been prescribed eye drops to treat glaucoma, use them as recommended by your doctor or pharmacist. It could save your eyesight!