Glaucoma

What is Glaucoma?

Glaucoma is a disease that damages the optic nerve. It happens when fluid builds up in the front part of the eye, known as the anterior chamber, between the cornea and the lens. The increased fluid causes pressure in the eye, which may damage the optic nerve. This nerve at the back of the eye transmits light signals to the brain, enabling us to see.

Glaucoma is a leading cause of blindness in people over sixty years old, but early treatment can often prevent blindness from glaucoma.

Lens

cornea

Optic nerve

Anterior Chamber

Drainage Angle

What causes Glaucoma?

Our eyes constantly produce a fluid called aqueous humour. As new aqueous fluid flows into the eye, the same amount should drain out through the "drainage angle." This balance keeps the pressure in the eye (intraocular pressure or IOP) stable. However, if the drainage angle is not functioning properly, fluid builds up, causing pressure inside the eye to rise and potentially damaging the optic nerve. Glaucoma damage is permanent. However, timely diagnosis and treatment can help to stop further damage.

Glaucoma is often called the 'silent thief of sight' because it usually has no symptoms in its early stages. About half of the people with glaucoma don't know they have it. Regular eye exams are essential for detecting this disease before it leads to vision loss.

Types of Glaucoma

There are two main types of glaucoma: closed-angle and open-angle glaucoma.

Open-angle glaucoma

The more common form of glaucoma is a slowly progressive, painless disease that causes no vision loss initially. However, the increased pressure gradually damages the optic nerve. Some people can have optic nerves sensitive to normal eye pressure and develop a type of open-angle glaucoma called normal tension glaucoma.

Closed/narrow-angle glaucoma

This glaucoma occurs when the iris moves forward and narrows the drainage angle. The iris may block the drainage angle completely, resulting in a sudden rise in intraocular pressure. This condition is called acute angle closure, an eye emergency that may result in permanent vision loss. Signs of acute angle close include:

Sudden onset of blurry vision
Severe eye pain
Headache
Seeing halos around lights
Nausea
Vomiting

Closed-angle glaucoma can also develop slowly, a condition called chronic angle-closure glaucoma. There may be no symptoms initially until the damage is severe or acute angle closure develops.

Glaucoma Suspects

Patients with intraocular pressure higher than normal but without optic nerve damage are considered glaucoma suspects. Similarly, patients with normal pressure may also be regarded as glaucoma suspects if their optic nerve appearance is unusual. It is essential to monitor the eyes of glaucoma suspects, as they are at a higher risk of developing glaucoma.

How is glaucoma diagnosed?

The diagnosis of glaucoma is based on a complete eye examination, which includes measuring the intraocular pressure and assessing the drainage angle and the optic nerve. Additional tests, such as visual field testing and scans of the optic discs, are also conducted to confirm the diagnosis and monitor for any progression.

How is glaucoma treated?

Glaucoma treatment aims to prevent further damage to vision and the optic nerve. Unfortunately, glaucoma damage is irreversible, so timely diagnosis and appropriate care are essential to prevent further harm. There are several treatment options for glaucoma:

Medication

Glaucoma is typically managed with daily use of eye drop medication. These eye drops work by lowering eye pressure. Some achieve this by decreasing the production of aqueous fluid in the eye, while others help improve fluid flow through the drainage angle to reduce pressure. These drops may have side effects such as:

Stinging or itching sensation
Red eyes or red skin around the eyes
Pulse and heartbeat changes
Changes in energy level
Worsening asthma symptoms
Dry mouth
Blurred vision
Eyelash growth
Changes in your eye colour, the skin around your eyes, or eyelid appearance

Glaucoma medications should be taken continuously; an ophthalmologist, optometrist, or GP can renew your prescription. If you are experiencing any side effects, your glaucoma medications can be changed, or an alternative treatment, such as a laser treatment, can be considered.

Laser Procedures

There are two main types of laser surgery for treating glaucoma. These procedures, which help drain aqueous fluid from the eye, are performed in the clinic.

Laser Trabeculoplasty

This procedure can be performed for open-angle glaucoma and can be used instead of or in addition to medications. The laser treatment improves the aqueous flow through the drainage and reduces the intraocular pressure. Laser trabeculoplasty can take 6 to 8 weeks to be fully effective.

Laser iridotomy

This procedure treats angle-closure glaucoma and can prevent it in patients with a "narrow-angle" at risk for angle-closure. The laser creates a small hole in the iris, which helps open the drainage angles, improves aqueous drainage, and lowers intraocular pressure.

Glaucoma Surgery

Glaucoma surgery can lower intraocular pressure by improving aqueous drainage through the drainage angle or creating an alternative drainage for aqueous fluid. These surgeries are performed in the operating theatre.

Trabeculectomy

A small hole is created in the sclera (the white part of the eye), which allows fluid to flow under the conjunctiva (the transparent membrane covering the sclera) and forms a bubble in the conjunctiva called a filtration bleb. The bleb is usually hidden under the upper eyelid. Aqueous fluid drains out of the eye into the bleb and is absorbed by the surrounding tissue, effectively reducing the intraocular pressure.

Glaucoma Drainage Device

These devices drain fluid from the eye through a small tube to a collection area called a reservoir under the conjunctiva. The liquid is then absorbed into nearby blood vessels.

Cataract Surgery

The natural lens is removed and replaced with an artificial lens during cataract surgery. This surgery can reduce eye pressure, particularly in eyes with narrow angles. Narrow angles happen when the iris and cornea are too close, which can block or narrow the drainage angle. Cataract surgery involves replacing the natural thick lens with a thin artificial lens. This helps open the drainage angle, allowing more space for fluid to leave the eye and reducing the pressure.

Minimally Invasive Glaucoma Surgery (MIGS)

These newer surgeries were developed as a safer alternative to trabeculectomy and glaucoma drainage devices to lower intraocular pressure with fewer potential side effects and faster recovery. Most MIGS operations are designed to improve aqueous drainage from the eye. MIGS can be combined with cataract surgery to lower intraocular pressure and reduce or eliminate the need for glaucoma eye drops.