What is Glaucoma?
Glaucoma is actually a group of diseases (many different types) affecting the optic nerve. The optic nerve carries images from the retina to the brain so we can see. In some types of glaucoma, increased pressure inside the eye affects the delicate tissues of the optic nerve. Glaucoma can damage nerve fibres, causing blind spots to develop. Often people don’t notice these blind areas until considerable optic nerve damage has already occurred. If the entire nerve is destroyed, blindness results.
Glaucoma is a leading cause of blindness in the world, especially in older people. Early detection and treatment are the keys to preventing optic nerve damage and blindness from glaucoma.
What Causes Glaucoma?
Mechanical compression and/or decreased blood flow of the optic nerve associated with other factors can lead to glaucoma. Although high eye pressure sometimes leads to glaucoma, as many as 50% of people with glaucoma have “normal” eye pressure.
What Are The Different Types Of Glaucoma?
Chronic open‑angle glaucoma is the most common glaucoma. The drainage angle of the eye can become less efficient with age, and pressure within the eye gradually increases. If this increased pressure results in optic nerve damage, it is known as chronic open‑angle glaucoma. Chronic open angle glaucoma can damage vision so gradually and painlessly that you are not aware of trouble until the optic nerve is already badly damaged.
Angle‑closure glaucoma results when the drainage angle of the eye becomes completely blocked. It is as though a sheet of paper floating near a drain suddenly drops over the opening and blocks the flow out from the sink. In the eye, the iris may act like the sheet of paper closing off the drainage angle. This results in a dangerously high eye pressure associated with pain, redness, low vision, and nausea.
Acute angle‑closure glaucoma occurs when the drainage angle of the eye suddenly becomes completely blocked and pressure builds up rapidly. The symptoms include severe eye pain, blurred vision, headache, rainbow haloes around lights, nausea and vomiting. Unless an ophthalmologist treats acute angle‑closure glaucoma quickly, blindness can result.
Chronic angle‑closure glaucoma results when the drainage angle of the eye gradually and painlessly becomes completely blocked and pressure builds up gradually. This form of glaucoma occurs more frequently in people of African and Asian ancestry.
Other Types of Glaucoma
Not all types of glaucoma are characterized by high intraocular pressures. In normal‑tension or low‑tension glaucoma, the optic nerve suffers damage with the resulting visual field loss even though normal intraocular pressures are maintained. It is believed that poor blood flow to the optic nerve causes this condition. Eyes afflicted with this condition are far more susceptible to optic nerve damage with any increase in the intraocular pressure than other eyes are. Only recently have scientists recognized how common normal tension glaucoma is and begun research into its causes and treatment.
Exfoliation syndrome is a common form of open angle glaucoma that results when there is a buildup of abnormal, whiteish material on the lens. This material and pigment from the back of the iris plug the drainage system of the eye, causing increased intraocular pressure. This form of glaucoma responds well to laser treatment.
Pigmentary glaucoma is a hereditary condition typically affecting young, nearsighted, Caucasian males. This condition is characterized by the iris being too large compared to the other structures of the eye. The iris is forced to bow backwards, coming into contact with the structures holding the lens in place. This disrupts the cells of the iris containing pigment, resulting in a release of pigment particles into the drainage system of the eye, which prompts an increase in intraocular pressure as the drainage system becomes clogged.
Other types of glaucoma may be caused by injuries to the eye, tumours, and other eye diseases. A rare type of glaucoma can even be present in children at birth.
Unfortunately, most cases of glaucoma offer no readily noticeable symptoms that warn of the irreversible damage being done. However, the presence of the following warning signs, indicate that you need a thorough examination by an optometrist:
- Loss of peripheral (side) vision
- Blind spots
- Difficulty in adjusting to a dark room
- Blurred vision
- Sore, reddened eyes
- Appearance of halos or rainbows around lights
- Severe headaches, nausea and eye pain (in rare cases)
The symptoms described above may not necessarily mean that you have glaucoma. However, if you experience one or more of these symptoms, contact the practice for a complete exam.
How Is Glaucoma Detected?
Regular eye examinations by your optometrist are the best way to detect glaucoma. We will measure your intraocular pressure (tonometry); estimate the drainage angle of your eye; evaluate any optic nerve damage (ophthalmoscopy); test the visual field of each eye (perimetry). Optic nerve photography and visual field testing should be performed at regular intervals to monitor changes in the optic nerve and the person’s overall vision. The information from these tests provides an indication of the effectiveness of any treatment being used and whether stronger measures may be necessary. Not all these tests are necessary for every person, nor at every visit. The object is to determine if glaucoma damage has increased during the time between your visits.
Who Is At Risk For Glaucoma?
High eye pressure alone does not mean that you have glaucoma. Your optometrist will put together many kinds of information to determine your risk for developing the disease. The most important risk factors include age, nearsightedness, African/Caribbean ancestry, family history of glaucoma, past injuries to the eyes, or a history of severe anaemia or shock. Your ophthalmologist will weigh all these factors before deciding if you need treatment for glaucoma; or whether you should be monitored regularly as a glaucoma suspect to detect the early signs of damage to the optic nerve.
The treatment for glaucoma, decided by a hospital ophthalmologist, depends upon the nature and severity of each case. As a rule, glaucoma cannot be cured, but it can be controlled. Eye drops, pills, laser procedures, and surgical operations are used to prevent or slow further damage from occurring. With any type of glaucoma, periodic examinations are very important to prevent vision loss. Because glaucoma can worsen without your being aware of it, your treatment may need to be changed over time.
Glaucoma is usually controlled with eye drops taken several times a day, sometimes in combination with pills. These medications will decrease eye pressure, either by slowing the production of aqueous fluid within the eye, or by improving the flow leaving the drainage angle. These medications work because you take them regularly and continuously. It is important to tell all of your doctors about the eye medications you are using. Glaucoma medications can have side-effects. You should notify your ophthalmologist immediately if you think you may be experiencing side-effects. Side-effects from some eye drops may include a stinging sensation; red eyes; blurred vision; headaches; changes in pulse, heartbeat or breathing. Side-effects from pills may include tingling of fingers and toes; drowsiness; loss of appetite; bowel irregularities; kidney stones; anaemia or bleeding.
You must continue to use your drops and/or tablets every day for them to be effective.
Laser surgery treatments may sometimes be effective for glaucoma treatment.
Trabeculoplasty is laser treatment to enlarge the eye drain itself to control pressure within the eye when treating open-angle glaucoma.
Iridotomy is laser treatment to create tiny holes in the iris to improve the flow of aqueous fluid to the drain.
When operative surgery is needed to control glaucoma, your ophthalmologist will use miniature instruments to create a new drainage channel for the aqueous fluid to leave the eye. The new channel helps to lower the pressure inside the eye. Complications of glaucoma surgery are rare, but as with any surgery they can occur. Surgery will be recommended only if your ophthalmologist feels that it is safer to operate than to allow optic nerve damage to continue.