All About Glaucoma

What is Glaucoma?

Ans: Glaucoma is a group of diseases that damage the eye’s optic nerve and may cause impaired vision and even blindness if left untreated. It is often associated with high Intraocular Pressure (IOP) in the eye (> 21 mm Hg).

GLAUCOMA = OPTIC NERVE DAMAGE

What is the symptom of Glaucoma and how can we detect it?

Ans: Glaucoma is asymptomatic which occurs without noticeable symptoms appearing until the disease is quite advanced. It has been called as the “silent thief of sight” because the loss of vision often occurs gradually over a long period of time. People with advanced Glaucoma will experience loss of side vision (peripheral vision), and can progress to loss of central vision and blindness if Glaucoma is not diagnosed and treated.

Glaucoma can only be diagnosed through a comprehensive eye examination which  include Visual Acuity Test (check for vision at various distances), Visual Field Test (check for areas of vision lost), Dilated Eye Exam & Nerve-Function OCT Scans (examine retina and optic nerve for damage), Tonometry (measure intraocular pressure), and Pachymetry (measure corneal thickness).

What causes Glaucoma?

Ans: The main reason of Glaucoma formation is due to the elevated Intraocular Pressure (IOP) that is caused by the failure of eye to maintain an appropriate balance between the amounts of aqueous humor (the clear fluid inside the eye) produced and the amounts that drain away. The fluid is produced by the ciliary body and exits the eye through the drainage angle, which is the angle formed inside the anterior chamber, between the iris and the peripheral cornea. The IOP increases when either too much fluid is produced in the eye or the drainage channels (Trabecular Meshwork) of the eye become blocked, thus damaging the optic nerve, which is made up of more than a million tiny nerve fibers. The patient will develop blind spots in his/her vision as these nerve fibers die and could become blind if all of the fibers die.

How many types of Glaucoma are discovered so far? What is the difference between them?

Ans: There are 2 major types of Glaucoma:

• Open-angle Glaucoma

The most common form of the disease. The drainage angle formed by the cornea and iris remains open but the Trabecular Meshwork is partially blocked, resulting in the build-up of the eye pressure and the subsequent damage of the optic nerve. This type of Glaucoma is painless and causes no vision changes at first. Regular eye check ups are essential to find early signs of damage to the optic nerve.

• Angle-closure Glaucoma / Closed-angle Glaucoma / Narrow-angle Glaucoma

It occurs when the iris bulges forward to narrow or block the drainage angle formed by the cornea and iris, thereby preventing the fluid from circulating through the eye and causing the Intraocular Pressure (IOP) to increase. It may occur suddenly as an acute attack or gradually as a chronic angle closure Glaucoma. An acute attack happens when the drainage angle gets completely blocked and the IOP rises drastically. It is a medical emergency and can be triggered by a sudden dilation of your pupils. Chronic angle closure Glaucoma are no symptoms at first, so the patient might not realize until the damage is severe or get attacked. Angle-closure Glaucoma can cause blindness if not treated right away.

What is the prevalence of Glaucoma in Singapore? What age group does it affect mainly?

Ans: Glaucoma affects up to 7% of Singaporeans above the age of 50 years old. For Singaporean Chinese, 60% of adult-blindness is caused by Glaucoma and Singapore has one of the highest rate of angle closure Glaucoma worldwide. The statement is supported by the study done by Asia-Pacific Glaucoma Society (APGS) whereby the incidence rate of angle closure Glaucoma (given as cases/100,000 persons/year for the population aged 30 years and older) range from 4.7 in Europe (Finland) to 15.5 in Chinese Singaporeans. On the other hand, Malay and Indian people in Singapore have lower rates than Chinese Singaporeans (6.0 and 6.3, respectively).

Treating Glaucoma

Glaucoma treatment often starts with prescription eyedrops. It works either by reducing the production of the aqueous fluid or by increasing the drainage of the fluid out of the eye.

Besides, there are three main types of laser therapy for Glaucoma to help aqueous drain from the eye and usually done in the Ophthalmologist’s office or at an outpatient surgery centre.

Laser Iridotomy is applied for people who have angle-closure Glaucoma. It involves making a hole in the iris by laser to allow fluid to drain normally in eyes and reduce the eye pressure.

Arrow pointing to the hole made by the laser.

Meanwhile, Laser Trabeculoplasty is used to treat people who have open-angle Glaucoma. This procedure is a quick, relatively painless, and safe method of lowering the IOP. In some cases, it is used as the initial or primary therapy for open-angled Glaucoma. With the eye numbed by anaesthetic eyedrops, the laser treatment is applied through a mirrored contact lens to the angle of the eye. Microscopic laser burns to the drainage angle, allowing fluid to be drained away more effectively. However, the effect of Laser Trabeculoplasty can only last about two years.

There are 2 types of Laser Trabeculoplasty: argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT). Many reports suggest that both ALT and SLT have similar IOP-lowering effects, however there are many problems associated with ALT, including irreversible damage to the eye, along with permanent scarring in the angle. In contrast, SLT is less likely to produce scarring in the angle, thus it can be repeated multiple times.

Laser Trabeculoplasty ( SLT)

Laser cyclo-ablation (also known as ciliary body destruction or cyclophotocoagulation) is another form of laser therapy applied for patients with severe forms of Glaucoma with poor visual potential. This procedure involves applying laser burns to the ciliary body, the part of eye that produces the aqueous fluid, destroying the cells that make the fluid, thus reducing the eye pressure. It is performed after other traditional therapies have failed.

Besides than laser therapy, there are some Glaucoma surgeries which are done in an operating theatre. Trabeculectomy is a filtering surgery where a tiny flap is created in the sclera (white of the eye) and part of the Trabecular Meshwork is removed. A bubble (like a pocket) will also be created in the conjunctiva which is known as a filtration bleb. It is usually hidden under the upper eyelid and cannot be seen. Aqueous humor could be drained out of the eye through the flap and into the bleb. In the bleb, the fluid is absorbed by tissue around your eye, thus lowering eye pressure.

TRABECULECTOMY GLAUCOMA SURGERY.

On the other hand, the eye surgeon could insert a tiny drainage tube in your eye to create a new pathway for fluid to exit the eye. The fluid is then sent to a collection area (reservoir) beneath the conjunctiva and absorbed into blood vessels nearby. Mini shunts without a reservoir are also used to improve safety and to reduce the post-surgery chance of pressures that are too low.

In recent years, minimally-invasive glaucoma surgery (MIGS) involves various devices such as the iStent Micro-Stent, the Xen glaucoma implant, the Hydrus Microstent, the InnFocus Microshunt,  have shown promising results. MIGS mainly refers to the procedures that are bleb-independent, including trabecular bypass stents and supra choroidal shunts, which aim to prevent the major bleb-related complications. It is directed at creating openings in the trabecular meshwork, the drainage ring in the wall of the angle of the eye, providing an alternate surgical procedure in lowering eye pressure. To date, the iStent and Trabectome are FDA approved and so far have shown modest short term IOP lowering especially when combined with cataract surgery.

Can the lost vision be recovered after treatment?

Ans: Damage to the optic nerve and vision impairment from Glaucoma are irreversible and cannot be restored.

Is Glaucoma curable?

Ans: To date, Glaucoma is incurable but it is controllable if you diagnose and treat it early.

What are the risk factors of glaucoma?

Ans: The risk factors of Glaucoma include:

• Advanced age (>40)
• Genetics (having family member with glaucoma)
• African or Hispanic heritage
• Have high eye pressure
• Severe myopia (short-sightedness) or hyperopia (long-sightedness)
• Have had an eye injury
• Have corneas that are thin in the center
• Have thinning of the optic nerve
• Have diabetes, migraines, poor blood circulation or other health problems affecting the whole body

Is there any initiative that could be taken to prevent Glaucoma?

Ans: No, but you can take some self-care steps to help you detect it early and slow its progress. Regular comprehensive eye exams can help to detect glaucoma in its early stages before irreversible damage occurs. It is suggested to get comprehensive eye checks every 2-3 years beginning at age 40 and every 2 years from age 65. You may need more frequent screening if you’re at high risk of glaucoma. Besides, know your family’s eye health history as glaucoma tends to run in families. Exercise safely and take prescribed eyedrops regularly. Wear eye protection when necessary as serious eye injuries can lead to Glaucoma.