Glaucoma is a disease of the eye in which fluid pressure within the eye rises - if left untreated the patient may lose vision, and even become blind. The disease generally affects both eyes, although one may have more severe signs and symptoms than the other.
There is a small space in the front of the eye called the "anterior chamber". Clear liquid flows in-and-out of the anterior chamber, this fluid nourishes and bathes nearby tissues. If a patient has glaucoma, the fluid does not drain properly - it drains too slowly - out of the eye. This leads to fluid build-up, and pressure inside the eye rises. Unless this pressure is brought down and controlled, the optic nerve and other parts of the eye may become damaged, leading to loss of vision.
There are two main types of glaucoma, open angle and closed angle (angle closure) glaucoma. The fluid in the eye flows through an area between the iris and cornea, where it escapes via the trabecular meshwork - "angle" refers to this area. The trabecular meshwork is made of sponky tissue lined by trabeculocytes. Fluid drains into s set of tubes, known as Schlemm's canal, from which they flow into the blood system.
Closed Angle Glaucoma (acute angle-closure glaucoma) can come on suddenly, and the patient commonly experiences pain and rapid vision loss. Fortunately, the symptoms of pain and discomfort make the sufferer seek medical help, resulting in prompt treatment which usually prevents any permanent damage from occurring.
Primary Open Angle Glaucoma (chronic glaucoma) - progresses very slowly. The patient may not feel any symptoms; even slight loss of vision may go unnoticed. In this type of glaucoma, many people don't get medical help until some permanent damage has already occurred.
Low-tension glaucoma - this is another form that experts do not fully understand. Even though eye pressure is normal, optic nerve damage still occurs. Perhaps the optic nerve is over-sensitive or there is atherosclerosis in the blood vessel that supplies the optic nerve.
Pigmentary glaucoma - this type generally develops during early or middle adulthood. Pigment granules, which arise from the back of the iris, are dispersed within the eye. If these granules build up in the trabecular meshwork, they can undermine the flow of fluids in the eye, leading to a rise in eye pressure. Running and some other sports can unsettle the granules, which get into the travecular meshwork.
Glaucoma has been called the silent thief of sight
- Primary glaucoma - this means we do not know what the cause was.
- Secondary glaucoma - the condition has a known cause, such as a tumor, diabetes, an advanced cataract, or inflammation.
Symptoms of glaucoma
How a person with advanced vision loss from glaucoma sees the same thing. Image credits: National Eye Institute, National Institutes of Health
A symptom is something the sufferer experiences and describes, such as pain, while a sign is something others can identify, such as a rash or a swelling.
The signs and symptoms of primary open angle glaucoma and acute angle-closure glaucoma are quite different.
Signs and symptoms of primary open-angle glaucoma
- Peripheral vision is gradually lost. This nearly always affects both eyes.
- In advanced stages, the patient has tunnel vision
Signs and symptoms of closed angle glaucoma
- Eye pain, usually severe
- Blurred vision
- Eye pain is often accompanied by nausea, and sometimes vomiting
- Lights appear to have extra halo-like glows around them
- Red eyes
- Sudden, unexpected vision problems, especially when lighting is poor
Glaucoma risk factors
A risk factor is something that raises the risk of developing a condition or disease. For example, obesity is a risk factor for diabetes type 2 - obese people have a higher risk of developing diabetes.
- Old age - people over the age of 60 years have a higher risk of developing the disease. For African-Americans, the risk rises at a younger age.
- Ethnic background - East Asians, because of their shallower anterior chamber depth, have a higher risk of developing glaucoma compared to Caucasians. The risk for those of Inuit origin is considerably greater still. People of African-American descent are three to four times more likely to develop the disease compared to American whites. Females are three times as likely to develop glaucoma as males.
- Some illnesses and conditions - people with diabetes or hypothyroidism have a much higher chance of developing glaucoma.
- Eye injuries or conditions - some eye injuries, especially severe ones, are linked to a higher glaucoma risk. Retinal detachment, eye inflammations and eye tumors can also cause glaucoma to occur.
- Eye surgery - some patients who underwent eye surgery have a higher risk of glaucoma.
- Myopia - people with myopia (nearsightedness) have a higher risk of glaucoma.
- Corticosteroids - patients on long-term corticosteroids have a raised risk of developing several different conditions, including glaucoma. The risk is even greater with eyedrops containing corticosteroids.
On the next page we look at the methods for diagnosing glaucoma, plus the available treatments for glaucoma, including eye drops and surgery.