Glaucoma refers to a group of disorders that lead to damage to the optic nerve, the nerve that carries visual information from the eye to the brain. Damage to the optic nerve causes vision loss, which may progress to blindness. Most people with glaucoma have increased fluid pressure in the eye, a condition known as increased intraocular pressure.
Glaucoma is the second most common cause of blindness in the US. There are four major types of glaucoma:
- Open angle (chronic) glaucoma
- Angle closure (acute) glaucoma
- Congenital glaucoma
- Secondary glaucoma
All four types of glaucoma are characterized by increased pressure within the eyeball, and therefore all can cause progressive damage to the optic nerve. Open angle (chronic) glaucoma is by far the most common type of glaucoma.
The front part of the eye is filled with a clear fluid called the aqueous humor. This fluid is constantly made in the back of the eye. It leaves the eye through channels in the anterior (front) chamber of the eye, and eventually drains into the bloodstream. The channels that drain the aqueous humor are in an area called the anterior chamber angle, or simply the angle.
In open angle glaucoma, the channels in the angle gradually narrow with time, making it hard for the fluid to drain properly. The buildup of fluid causes increased pressure in the eye. This increased pressure pushes on the junction of the optic nerve and the retina at the back of the eye, reducing the blood supply to the optic nerve.
As the optic nerve deteriorates due to decreased blood supply, blind spots develop in the field of vision. Peripheral (side) vision is affected first. This is usually not noticed until quite a bit of vision is lost. If the disease is not diagnosed and treated, a lot of vision may be lost before the person becomes aware of a problem.
Open angle glaucoma tends to run in families. Your risk is higher if you have a parent or grandparent with open angle glaucoma. People of African descent are at particularly high risk for this disease.
Angle closure (acute) glaucoma is caused by a shift in the position of the iris of the eye that suddenly blocks the exit of the aqueous humor fluid. This causes a quick, severe, and painful rise in the pressure within the eye (intraocular pressure). Most people with angle closure glaucoma will also have redness and swelling in the affected eye. Nausea and vomiting may occur. Angle closure glaucoma is an emergency. This is very different from open angle glaucoma, which painlessly and slowly damages vision.
If you have had acute glaucoma in one eye, you are almost certainly at risk for an attack in the second eye, and your doctor is likely to recommend preventive treatment.
Dilating eye drops and certain systemic medications may trigger an acute glaucoma attack if you are at risk.
Secondary glaucoma is caused by other diseases, including eye diseases such as uveitis, systemic diseases, and drugs such as corticosteroids.
Congenital glaucoma, which is present at birth, is the result of abnormal development of the fluid outflow channels of the eye. Surgery is required for correction. Congenital glaucoma is often hereditary.
Sign & Symptoms :
- Most people have no symptoms
- Gradual loss of peripheral (side) vision
- Severe eye pain, facial pain
- Decreased or cloudy vision
- Red eye
- Swelling of the eye
- Pupil does not react to light
- Nausea and vomiting (may be the major symptom in the elderly)
- Sensitivity to light
- Red eye
- Enlargement of one eye or both eyes
- Cloudiness of the front of the eye
An examination of the eye may be used to diagnose glaucoma. However, checking the intraocular pressure alone (tonometry) is insufficient because eye pressure changes. Examination of the inside of the eye by looking through the pupil, often while the pupil is dilated, is needed.
Usually a complete examination of the eyes will be done.
The objective of treatment is to reduce intraocular pressure. Depending on the type of glaucoma, this is achieved by medications or by surgery.
Open angle glaucoma treatment:
Most people with glaucoma can be treated successfully with eye drops. In the past, eye drops for glaucoma caused blurring of vision, but most eye drops used today have few side effects. Your doctor will evaluate your medical history and determine the best drops for you. You may need more than one type of drop. Some patients may also be treated with pills to lower pressure in the eye.
Newer drops and pills are being developed that directly protect the optic nerve from glaucoma damage.
Some patients will need additional forms of treatment, such as a laser treatment, to help open the fluid outflow channels. This procedure is usually painless. Others may need traditional surgery to open a new outflow channel.
Angle closure glaucoma treatment:
Acute angle closure attack is a medical emergency. Blindness will occur in a few days if it is not treated. Drops, pills, and medicine given by IV are used to lower pressure. The patient may also need an emergency operation, called an iridotomy. This procedure uses laser to open a new channel in the iris. The new channel relieves pressure and prevents another attack.
This form of glaucoma is almost always treated with surgery to open the outflow channels of the angle. This is done with anesthesia (asleep and no pain).
There is no way to prevent open angle glaucoma, but vision loss from open angle glaucoma can be prevented. Early diagnosis and careful management of the condition, if diagnosed, are the keys to preventing vision loss.
Most people with open angle glaucoma have no symptoms. All persons over 40 should have an eye examination at least every 5 years, and more often if in a high-risk group.
People at high risk for acute glaucoma may opt to undergo iridotomy before having an attack. Patients who have had an acute episode in the past may undergo the procedure to prevent recurrence.
Risk Factor :
Those in high-risk groups include people with a family history of open angle glaucoma and people of African heritage.