Glaucoma – The Silent Thief
Glaucoma can steal your vision gradually without you ever noticing, until it is too late.
What is Glaucoma?
Glaucoma is a complicated disease in which damage to the optic nerve leads to progressive, irreversible vision loss. It is the second leading cause of blindness in Canada and affects 400,000 Canadians and 67 million people worldwide.
There are several types of glaucoma. The two main types are open-angle and angle-closure and both types are marked by an increase in intraocular presssure.
Primary open-angle glaucoma
By far the most common type of glaucoma (90%) is primary open-angle glaucoma which develops gradually and painlessly. The human eye is constantly producing fluid inside the walls of the eye, called aqueous fluid. But if too much of this fluid is being produced within the eye, or if the fluid is not draining properly, it can put pressure on the optic nerve. One theory for how this might occur is that glaucoma is thought to develop when the eye’s drainage system becomes inefficient over time. The optic nerve transmits all of the information the eye sees, and sends that information to the brain. When the optic nerve is damaged, the amount and quality of information sent to the brain decreases, and a loss of vision occurs. Usually peripheral vision is affected first, followed by central vision during the later stages of the disease. Most people have no noticeable symptoms until they have irreversibly lost a lot of vision. This type of glaucoma if detected early usually responds well to medication.
Acute angle-closure glaucoma
Acute angle-closure glaucoma results from a sudden blockage of the drainage channels within your eye. While it is not as common as primary open angle glaucoma it is considered a medical emergency that can cause vision loss within a day. Angle-closure glaucoma happens when the drainage angle in the eye (formed by the cornea and the iris) closes or becomes blocked. With age, the lens in the eye becomes larger, pushing the iris forward and narrowing the space between the iris and the cornea. As this angle narrows, the aqueous fluid is blocked from exiting through the drainage system, resulting in a buildup of fluid and an increase in eye pressure. Angle-closure glaucoma can be chronic (progressing gradually) or acute (appearing suddenly). Symptoms of angle closure may include headache,eye pain, nausea, rainbows around lights at night and blurred vision. Treatment of angle closure needs to be done immediately or significant vision loss can occur. Treatment usually involves either a laser or surgery to remove a small portion of the bunched up iris.
During our comprehensive eye examinations, we look at this part of the eye to ensure you are not at risk of developing this emergency event and can send you to an ophthalmologist for preventive treatment to avoid this occurring.
Normal Tension Glaucoma(NTG)
This is also called low tension or normal pressure glaucoma. In this glaucoma the optic nerve is damaged even though the pressure is not very high. It is unknown why this damage occurs. For some reason the optic nerve is susceptible to damage from even the normal amount of eye pressure. Those at highest risk for this type of glaucoma are: people with a family history of normal-tension glaucoma, people of Japanese ancestry, people with a history of systemic heart disease. Since little is known about why normal pressure damages some eyes, most doctors lower eye pressure as much as possible using drops and laser or conventional surgery.
This type of glaucoma occurs in babies when there is incorrect or incomplete development of the eye’s drainage canals during the prenatal period. This is a rare condition that may be inherited. Microsurgery is usually performed to correct the structural defects.
Other Types of Glaucoma
- Pigmentary Glaucoma (pigment from the iris blocks the drainage of the fluid and IOP rises)
- Pseudoexfoliation Glaucoma
- Traumatic Glaucoma
- Neovascular Glaucoma (uncontrolled diabetes)
- Irido Corneal Endothelial Syndrome (ICE)
Why is glaucoma harmful to vision?
The optic nerve, located at the back of the eye, carries visual information to the brain. As the fibers that make up the optic nerve are damaged by glaucoma, the amount and quality of information sent to the brain decreases and a loss of vision occurs. This could be loss of visual clarity and brightness, gaps in vision, loss of a section of your vision or eventually if not detected and treated complete loss of vision.
Will I go blind from glaucoma?
If diagnosed at an early stage, glaucoma can be controlled and little or no further vision loss should occur. If left untreated, side awareness (peripheral vision) and central vision will be destroyed and blindness may occur.
How is glaucoma detected?
Tests for glaucoma are part of a comprehensive eye examination. A simple and painless procedure called tonometry measures the internal pressure of your eye. Ophthalmoscopy examines the back of the eye to observe the health of the optic nerve. Biomicroscopy of the front structures of the eye are evaluated for possible risk factors for glaucoma. A visual field test, a very sensitive test that checks for the development of abnormal blind spots, may also be completed. Imaging of the optic nerve with photography and Optical Coherence Tomography (OCT) also provides additional information to confirm a diagnosis.
Risk Factors for Glaucoma
- Age – People over the age of 60 are at increased risk for the disease with the risk of developing glaucoma increasing slightly with each year.
- Family history – Having a family history of glaucoma increases the risk of developing glaucoma.
- Medical conditions – Some studies indicate that diabetes may increases the risk of developing glaucoma, as does variations in blood pressure (high and low) and heart disease.
- Physical injuries to the eye—Severe trauma, such as being hit in the eye, can result in immediate increased eye pressure and future increases in pressure due to internal damage. Injury can also dislocate the lens, closing the drainage angle, and increasing pressure.
- Other eye-related risk factors—Eye anatomy, namely corneal thickness and optic nerve appearance indicate risk for development of glaucoma. Conditions such as retinal detachment, eye tumors, and eye inflammations may also induce glaucoma. Some studies suggest that high amounts of nearsightedness may also be a risk factor for the development of glaucoma.
- Corticosteroid use – Using corticosteroids for prolonged periods of time appears to put some people at risk of getting secondary glaucoma.
How is glaucoma treated?
Glaucoma is usually treated with prescription eye drops and medicines. The goal of the treatment is to prevent loss of vision by lowering the pressure in the eye. The type of medication may change if it is not providing enough pressure reduction or if side-effects are being experienced.
Surgery may help lower pressure when medication is not enough, however it cannot reverse vision loss.
- Laser surgery – Laser trabeculoplasty helps to drain fluid out of the eye. A laser beam is used to stimulate the trabecular meshwork (an area of tissue in the eye located around the base of the cornea, near the ciliary body. It is responsible for draining the eye) to help it to work more efficiently at fluid drainage. The results may be somewhat temporary, and the procedure may need to be repeated.
- Conventional surgery – If medication and laser surgery aren’t effective in controlling eye pressure, a filtering procedure called a trabeculectomy may be required. Filtering microsurgery involves creating a drainage flap, allowing fluid to percolate into and later drain into the vascular system.
- Drainage implants – Another type of surgery, called drainage valve implant surgery, may be appropriate for people with uncontrolled glaucoma, secondary glaucoma or for children with glaucoma. A small silicone tube is inserted in the eye to help drain aqueous fluid.
Will my vision be restored after treatment?
Unfortunately, any vision loss as a result of glaucoma is permanent and cannot be restored. This is why regular eye examinations are important.
Glaucoma cannot be prevented, but early detection and treatment can control glaucoma and reduce the chances of damage to the eye and a loss of sight.