Glaucoma

Glaucoma is a serious eye disease and a common cause of blindness. It is responsible for 20% of blindness in Singapore.
Glaucoma is caused by damage to vision due to too much pressure within the eye. If it is detected early, treatment can prevent or reduce loss of vision in most patients.
Glaucoma is known as the ''thief of sight" as it silently and painlessly reduces vision without the patient realising it until damage is advanced.
Causes
The ciliary body pumps aqueous fluid into the eye. This drains out of the eye through the trabecular meshwork (the eye's drainage system) at the angle of the eye.
Glaucoma occurs when the amount of fluid pumped in exceeds that flowing out, increasing eye pressure. This increased pressure results in damage to the delicate nerve fibres of the optic nerve leaving the back of the eye. Once the nerve fibres are damaged, they cannot recover.
Types
Open angle glaucoma
This is the most common type of glaucoma. Open angle glaucoma occurs when the eye's. drainage canals become clogged over time. The Inner eye pressure (also called intraocular pressure) ris~s because the correct amount of fluid is unable to drain out of the eye. Most people have no symptoms and no early warning signs.
This type of glaucoma develops slowly and sometimes without noticeable sight loss for many years. If open angle glaucoma is not diagnosed and treated, it can cause a gradual loss of vision.
Angle closure glaucoma
This type of glaucoma is also known as acute glaucoma or narrow angle glaucoma. It is rarer and is very different from open angle glaucoma In that the eye pressure usually rises very quickly.
With angle closure glaucoma, the iris is not as wide and open as it should be.
The outer edge of the iris bunches up over the drainage canals, when the pupil enlarges too much or too quickly. This can happen when entering a dark room.
Normal pressure glaucoma
This is seen in people with unusually sensitive optic nerves wich could be damaged even though intraocular pressure is within a normal range.
Other forms of glaucoma
Congenital glaucoma is due to faulty development of the trabecular meshwork and is detected in the first 6 months of life.
Secondary glaucoma is due to other diseases of the eye. It may also be caused by medications. The high eye pressure caused by the underlying condition causes the same optic nerve damage as primary glaucoma.
Diagnosis
Diagnosis is made after assessment pressure, optic nerve and visual field. Eye pressure may vary depending on the time of day. The drainage angle can be examined by your specialist to see if it is blocked. If intraocular pressure is raised, along with evidence of optic nerve damage, then diagnosis is straightforward.
Very early damage to peripheral vision may only be detectable on visual field testing. Repeat examinations over time may be required to determine the diagnosis, especially in cases where pressure is only slightly high. People with a family history of glaucoma should be screened regularly for glaucoma, as early detection and treatment can prevent visual loss.
Treatment
Medical Treatment
Most cases of glaucoma can be successfully treated with eye drops. Eye medication works by either reducing the production of aqueous fluid, or improving drainage from the eye.
Tablets may be required if rapid eye pressure control is required. These are more likely to cause side effects, as they have to be absorbed through the body.
Both eye drops and tablets can interact with other medications you may be taking. Read the information accompanying your medication provided by the manufacturer and tell your family doctor or other specialists that you are on glaucoma treatment.
Surgery
Surgery involves either laser treatment or making a cut in the eye to reduce the intraocular pressure. It is required if medication alone is not adequately controlling the pressure.
Laser Treatment for Glaucoma includes:
Laser Trabeculoplasty - a laser beam directed at the trabecular meshwork selectively in small areas improves the drainage of aqueous fluid and lowers intraocular pressure.
Laser Iridotomy - a small hole is made at the edge of the iris to allow aqueous fluid to escape from the eye in patients with angle closure glaucoma. This is also done in patients at risk of acute angle closure glaucoma to prevent a future attack.
Surgery creates a channel in the sclera of the eye, near the trabecular meshwork for the drainage of fluid from the eye. This is commonly known as a filtering procedure or trabeculectomy. Injections may be required to stop the channel from healing itself. If one or two trabeculectomies do not work, a valve may need to be inserted to maintain the channel.
Compiled by
Dr F I Biswas

Glaucoma

Glaucoma is a serious eye disease and a common cause of blindness. It is responsible for 20% of blindness in Singapore. Glaucoma is caused by damage to vision due to too much pressure within the eye. If it is detected early, treatment can prevent or reduce loss of vision in most patients. Glaucoma is known as the thief of sight as it silently and painlessly reduces vision without the patient realising it until damage is advanced. Causes The ciliary body pumps aqueous fluid into the eye. This drains out of the eye through the trabecular meshwork (the eyes drainage system) at the angle of the eye. Glaucoma occurs when the amount of fluid pumped in exceeds that flowing out, increasing eye pressure. This increased pressure results in damage to the delicate nerve fibres of the optic nerve leaving the back of the eye. Once the nerve fibres are damaged, they cannot recover. Types Open angle glaucoma This is the most common type of glaucoma. Open angle glaucoma occurs when the eyes. drainage canals become clogged over time. The Inner eye pressure (also called intraocular pressure) ris~s because the correct amount of fluid is unable to drain out of the eye. Most people have no symptoms and no early warning signs. This type of glaucoma develops slowly and sometimes without noticeable sight loss for many years. If open angle glaucoma is not diagnosed and treated, it can cause a gradual loss of vision. Angle closure glaucoma This type of glaucoma is also known as acute glaucoma or narrow angle glaucoma. It is rarer and is very different from open angle glaucoma In that the eye pressure usually rises very quickly. With angle closure glaucoma, the iris is not as wide and open as it should be. The outer edge of the iris bunches up over the drainage canals, when the pupil enlarges too much or too quickly. This can happen when entering a dark room. Normal pressure glaucoma This is seen in people with unusually sensitive optic nerves wich could be damaged even though intraocular pressure is within a normal range. Other forms of glaucoma Congenital glaucoma is due to faulty development of the trabecular meshwork and is detected in the first 6 months of life. Secondary glaucoma is due to other diseases of the eye. It may also be caused by medications. The high eye pressure caused by the underlying condition causes the same optic nerve damage as primary glaucoma. Diagnosis Diagnosis is made after assessment pressure, optic nerve and visual field. Eye pressure may vary depending on the time of day. The drainage angle can be examined by your specialist to see if it is blocked. If intraocular pressure is raised, along with evidence of optic nerve damage, then diagnosis is straightforward. Very early damage to peripheral vision may only be detectable on visual field testing. Repeat examinations over time may be required to determine the diagnosis, especially in cases where pressure is only slightly high. People with a family history of glaucoma should be screened regularly for glaucoma, as early detection and treatment can prevent visual loss. Treatment Medical Treatment Most cases of glaucoma can be successfully treated with eye drops. Eye medication works by either reducing the production of aqueous fluid, or improving drainage from the eye. Tablets may be required if rapid eye pressure control is required. These are more likely to cause side effects, as they have to be absorbed through the body. Both eye drops and tablets can interact with other medications you may be taking. Read the information accompanying your medication provided by the manufacturer and tell your family doctor or other specialists that you are on glaucoma treatment. Surgery Surgery involves either laser treatment or making a cut in the eye to reduce the intraocular pressure. It is required if medication alone is not adequately controlling the pressure. Laser Treatment for Glaucoma includes: Laser Trabeculoplasty - a laser beam directed at the trabecular meshwork selectively in small areas improves the drainage of aqueous fluid and lowers intraocular pressure. Laser Iridotomy - a small hole is made at the edge of the iris to allow aqueous fluid to escape from the eye in patients with angle closure glaucoma. This is also done in patients at risk of acute angle closure glaucoma to prevent a future attack. Surgery creates a channel in the sclera of the eye, near the trabecular meshwork for the drainage of fluid from the eye. This is commonly known as a filtering procedure or trabeculectomy. Injections may be required to stop the channel from healing itself. If one or two trabeculectomies do not work, a valve may need to be inserted to maintain the channel. Compiled by Dr F I Biswas