Can glaucoma be cured, or can it only be managed?

In this article, consultant ophthalmologist, Mr Amar Alwitry, details what glaucoma is, and how it affects the eye.

What is glaucoma, and how does it affect the eye?

In normal eyes, the production of aqueous corresponds to the drainage, and is maintained at a relatively constant level. Normal intraocular pressure (IOP) is usually between 15mm and 21mm of mercury (mmHg). Normally, there is a diurnal fluctuation in IOP, with the pressure at its highest point in the morning, which then reduces throughout the day.

In some people, the balance between production and drainage is disturbed: either the aqueous production is excessive or the drainage is deficient. Usually, it is the latter that is the problem. Any imbalance will result in raised IOP, with a variety of consequences depending on the degree of pressure rise, its rapidity of onset, and the individual susceptibility of the patient’s eye to that raised pressure.

Some people can have a raised pressure without any problems occurring. These people have ocular hypertension – high pressure in the eye but no damage. Others with a similar or even lower pressure can develop damage to the optic nerve. The pressure compresses the optic nerve as it enters the eye and the nerve fibres start dying off. This is asymptomatic so you do not know it is happening.

If the process continues unchecked, then you can start losing patches of your peripheral vision. We assess this with regular visual field tests. The big problem with glaucoma is that the visual field loss is not noticeable. If untreated, eventually the peripheral vision is completely lost and the central vision also becomes compromised. Glaucoma damage is irreversible and permanent, and so early detection and treatment are essential.

What are the main causes of glaucoma?

The main cause of glaucoma is related to the rise in pressure inside the eye, resulting in damage to the optic nerve. The vast majority of patients who develop glaucoma have no underlying risk factors or cause. These patients have primary open angle glaucoma.

Risk factors for open angle glaucoma include the following:

• age over 55
• black, asian or hispanic heritage
• family history of glaucoma (gives a 1 in 5 chance if a first degree relative is affected)
• certain medical conditions, such as diabetes, migraines, high blood pressure, and sickle cell anaemia
• extreme short or long-sightedness
• eye injury or certain types of eye surgery
• taking steroid medicines, especially steroid eye drops, for a long time

What are the different types of glaucoma, and how do they differ?

There are many different types of glaucoma, but by far the most common is primary open-angle glaucoma. The fluid/aqueous leaves the eye through the drainage angle formed at the edge of the iris where it meets the cornea. It is formed of a sieve-like mechanism called the trabecular meshwork, and the aqueous fluid continually drains out through it. 

There is no physical obstruction to the fluid flow and the angle is open (hence the term open-angle). However, despite no blockage to fluid getting there, the sieve-mechanism itself/trabecular meshwork is clogged up. 

Angle-closure glaucoma is another common type of glaucoma. This form of glaucoma occurs when the drainage angle becomes physically obstructed due to the iris and peripheral cornea being too close to each other. The closing of the space means that no aqueous fluid can reach the drainage angle because the angle is “closed”.

In both circumstances, fluid builds up in the eye. As a result, the eye cannot stretch and therefore the pressure increases. Angle-closure glaucoma may occur suddenly (acute) or gradually (chronic).

Normal-tension glaucoma (or normal pressure glaucoma) is a form of glaucoma that occurs in a small number of patients, whereby the pressure in the eye remains normal, but the glaucoma damage to the optic nerve occurs nonetheless. We do not know exactly why this occurs, but we know it is related to blood flow. This emphasises the fact that it is a problem inherent within the nerve and is not purely about pressure.  Some patients with high pressure do not get glaucoma (ocular hypertensives) and others with normal pressure still develop glaucoma (normal pressure glaucoma).

Glaucoma in children is another kind of glaucoma. A child may be born with glaucoma or develop it in the first few years of life. Malformation of the trabecular meshwork, injury, or an underlying medical condition may cause the raised pressure and the optic nerve damage. In early life, the eye is not fully formed, and as such, may even stretch due to the pressure rise.

In pigmentary glaucoma, small pigment granules flake off from the iris and block or slow down fluid drainage from the eye by clogging up the trabecular meshwork/drainage angle of the eye. This means more fluid stays in the eye and the pressure goes up.

Can glaucoma be cured, or can it only be managed?

Unfortunately, glaucoma cannot be cured. The main target of our therapies is to reduce the pressure in the eye through medical therapies using topical eye drops initially. Some of these topical eye drops reduce the flow of fluid into the eye, while others increase the fluid outflow from the eye. 

Recently, the National Institute for Clinical Excellence (NICE) has recommended laser in the form of Selective Laser Trabeculoplasty (SLT) as a good therapy for reducing pressure without drops. We get the eye pressure down to a level we think is acceptable and safe. We then watch you carefully to make sure the glaucoma does not worsen. If it does, then we need to get the pressure even lower to stop it.

Are there any surgical options for treating glaucoma?

Yes. If medical or laser therapies do not work to lower the pressure in the eye to a safe level, surgery can be considered. The most successful (at lowering pressure) technique is called trabeculectomy, whereby a flap valve is created in the sclera (white bit) of the eye to allow fluid to drain out of the eye in a controlled manner to bring the pressure down.

This is, however, more risky than other newer techniques which involve less trauma to the eye. These are called minimally invasive techniques and called MIGS (minimally invasive glaucoma surgery) which aim to reduce the pressure without the risks of trabeculectomy. They involve the introduction of stents or tubes to allow fluid to leave the eye.

Cataract surgery alone often brings the pressure in the eye down, and sometime we can put special stents into the drainage network of the eye at the time of cataract surgery to improve glaucoma control in patients who have concurrent cataract.

To book a consultation with Mr Amar Alwitry, you can visit his Top Doctors profile to do just that today.