What is glaucoma?
Glaucoma is a common eye condition characterized by loss of vision secondary to damage to the optic nerve. The optic nerve at the back of the eye transmits images to the brain so that they can be perceived. Usually, but not always, damage to the optic nerve in glaucoma is caused by raised pressure within the eyeball.
The eye is like a ball filled with fluid which provides oxygen and nourishment to the rest of the eye. It has an inflow tap (ciliary body) and an outflow drain (trabecular meshwork). To maintain normal pressures, the inflow must balance the outflow. If the drainage is blocked, fluid accumulates and pressure in the eye builds up. This raised pressure may damage the optic nerve.
Glaucoma is commonly divided into two general types:
Acute Glaucoma
This is a common type of glaucoma in Singapore, and occurs more commonly in the middle-aged or elderly Chinese females especially those who are long-sighted. It is characterized by a sudden increase in the eyeball pressure, causing sudden onset of pain, redness and blurred vision in one or both eyes. The pain can be very severe and is often accompanied by headache, nausea and vomiting.
This sudden increase in eyeball pressure is due to acute blockage of the outflow of the fluid filling the eye. Damage to the optic nerve can occur, and urgent treatment to lower the pressure is essential to save vision.
Chronic Glaucoma
Chronic glaucoma is different from acute glaucoma in that there is no complaint of acute pain or redness. There are two main subsets, chronic open angle and chronic angle closure glaucoma. The latter is particularly common in Singapore and rapidly progresses to blindness if left untreated. In fact both are asymptomatic except for progressive vision loss. The side vision is usually affected first and central vision is maintained initially. The disease is often very advanced before visual loss is noted. That is why this disease is often called the thief of vision.
Other forms of glaucoma also exist, e.g. glaucoma secondary to other eye conditions such as inflammatory eye diseases or cataracts. In addition, glaucoma can affect newborns or infants.
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How is glaucoma diagnosed?
A glaucoma check comprises of several simple pain-free tests.
First, the pressure within the eye has to be measured (tonometry).
Gonioscopy involves the use of a special contact lens held against the eye. It enables the doctor to see the area where the fluid in the eye normally drains to see whether there is any blockage or narrowing.
The “all round” vision i.e. visual field can be assessed to determine whether any optic nerve damage has occurred. The test usually takes about 15 minutes per eye. The patient is asked to sit at a screen and fixate on a central target. A series of lights are presented at different parts of the vision in turn, and one will be asked to press a button if these are seen. This will detect any missing areas in the visual field.
Finally, the optic nerve head will be assessed. This is usually done after the pupils are dilated with eyedrops. The optic nerve can then be observed directly at the slitlamp with the help of lenses. Other methods include photography of the optic nerve head or computerized imaging.
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How is glaucoma treated?
Glaucoma can be treated but not cured. Once the optic nerve is damaged, the loss of vision is permanent. The aim of the treatment is to lower the intraocular pressures to an acceptable level, thus preventing further damage to the optic nerve. Because treatment can only control but not cure the condition, it must be continued throughout life.
Treatment depends on the type of glaucoma, and may be in the form of medication (eyedrops or tablets), surgery or laser.
Medication
The most common form of treatment is usually eye drops. Putting drops in as prescribed is essential in preventing any further deterioration in sight. Some of the eyedrops do have side-effects, and these arise because the drops are absorbed into the bloodstream. This absorption can be minimized by pressing a finger against the lower lid where it meets your nose, or by closing your eye for one minute after instilling the eyedrop. Any side effects should be reported to your doctor. It is important if there is more than one glaucoma eyedrop to instill them at least five minutes apart.
Surgery
In some forms of glaucoma an operation may be necessary. The most common surgery is trabeculectomy, where an opening is created for the fluid in the eye to escape into the surrounding tissues and absorbed. This allows the pressure inside in the eyeball to be relieved.
Newer kinds of surgery are available and include inserting a tube to drain the fluid from the eye. This is often indicated in complicated glaucomas.
Laser treatment
Various types of laser therapy are used in the treatment of glaucoma. It is used particularly in acute glaucoma. A channel is created inside the eye to allow fluid to drain and to prevent future attacks of glaucoma.
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Can glaucoma be prevented?
Glaucoma cannot be prevented, but visual loss can be prevented if treatment is started before optic nerve damage has occurred. Glaucoma can run in families and glaucoma genes have been identified.
Acute glaucoma
Seek urgent review by your doctor if you develop painful red eyes with blurred vision.
Chronic glaucoma
It is important to have your eyes checked regularly once you are over 40, especially if you have a relative who has glaucoma.
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