Glaucoma – all you need to know about the second leading cause of blindness

Glaucoma is the world’s second leading cause of blindness¹. According to the World Health Organization, around 4.5 million people globally suffer from blindness due to glaucoma. It is estimated that this number will rise to 11.2 million people by 2020. That’s a 149% increase—6.7 million more people who may be at risk of losing their vision to this "silent blinding disease", and they have no idea it's even happening.²  BETTER VISION explains what you should know about this group of eye diseases, eye pressure, and the causes, risk factors, screening methods and treatment associated with glaucoma.

Glaucoma is complex disease with many forms, but in short it can be defined as damage to the nerve connecting the eye to the brain (called the optic nerve) mostly due to eye pressure (intraocular pressure), which influences your visual field and visual acuity. The risk of getting glaucoma is six times more likely if you are over 60 years old.

To better understand how the optic nerve is damaged, consider the working of the eye:

The ciliary body produces a clear, watery liquid called aqueous humour in the front chamber that provides nutrition to various parts of the eye including the lens, cornea and ocular tissues. This fluid then drains from the eye through a spongy network called the trabecular meshwork and exits through Schlemm’s canal into the blood vessels.

Most commonly, glaucoma affects Schlemm’s canal or the trabecular meshwork, meaning that the aqueous humour can’t leave the eye as usual. Compare this to a cement dam with a blocked overflow – if it’s continuously pumped full of water that can’t drain, pressure will increase, and the dam wall will eventually burst. Similarly, when Schlemm’s canal or the trabecular meshwork is blocked it will cause a buildup of aqueous humour that will affect eye pressure which in turn damages the optic nerve and will influence your vision.  

There are two categories of glaucoma, closed-angle and open-angle glaucoma. Each category is defined by the position of the ocular lens and iris in relation to the trabecular meshwork³, which determines how the aqueous humour is drained from the eye or not.

Glaucoma cannot be prevented, but if you manage the risk factors associated with the eye disease, blindness can be avoided.

If you’re at a higher risk for developing glaucoma due to ethnicity, diabetes, your family history or age, for example, it’s important to go for regular glaucoma screenings.

Individual lifestyle factors can also play a role. Your risk of developing glaucoma can effectively be reduced by keeping high blood pressure at bay, managing sleep apnea and monitoring cortisone treatment with the help of your healthcare practitioner.

Warning signs to look out for include:

• Chronic headaches
• Blurred vision
• Pain behind the eye
• Teary eyes

If you experience any one, or a combination of these symptoms, visit your nearest eye care professional or eye doctor and ask for a glaucoma test.

Everyone should go for eye checkups regularly, including screening for glaucoma at least once every 2 years, especially if you are 40 years or older. The risk of glaucoma is even higher when you reach age 60, so discuss how often you should do a screening with your eye care professional.

If you wear glasses, you are probably checked for glaucoma each time you visit your eye care professional to update your lens prescription. But if you don’t have any visual issues, you are less likely to be screened regularly. Be aware of this and make a point of visiting an eye care professional near you for your screening even if you don’t wear glasses.

If you suffer from diabetes, are over 60 or have a family history of glaucoma, you should go for a screening once a year.

Treatment of glaucoma is individualised, and unlike something as straightforward as cataract surgery for example, no single ideal glaucoma treatment exists.

Following diagnosis, your eye specialist will determine the way forward depending on your unique situation. However, in general they will calculate an ideal target pressure, and attempt to manage or lower your eye pressure to reach that target. This can be done medically with eye drops or medication, surgically, or by using a combination of both options.

• Laser surgery  – where a laser is used to open clogged parts of the trabecular meshwork.  
• Minimal invasive glaucoma surgeries  – surgeries done with small devices making micro cuts to bypass or open blocked canals. This type of surgery is quick with minimal complications and fast recovery.
• Cutting surgeries  – where a cut is made to open the canal and lower pressure. This includes trabeculectomy, sclerectomy, and viscocanalostomy and canaloplasty. Consult your eye care specialist or eye doctor for more information.  
• Tube surgery  – where a tube is permanently placed in the eye to drain the aqueous humour and manage pressure.

In general, glaucoma chances of recovery after surgery can be good if all contributing factors are managed, but unfortunately damage to the optical nerve cannot be reversed.  

In addition to surgery, your eye specialist will treat the problem holistically and may recommend certain lifestyle adjustments. It’s important to give them a complete medical history and mention any of your hobbies and habits. For example, if you do yoga or play a wind instrument, it can actually influence your eye pressure.

As mentioned, diabetes mellitus, blood pressure (low and high), and chronic medication use must be managed. Quitting smoking, healthy eating habits and regular exercise is also recommended.

This article is purely intended to give a broad overview of glaucoma. Always consult your physician, eye health care professional or a qualified ophthalmologist with any questions you have regarding glaucoma and its diagnosis.

Dr Marissa Willemse  (MBChB (UP), FC(Ophth) SA, MMed (UL) is an ophthalmic surgeon and an executive member of the South African Glaucoma Society  who provided useful insights in the writing of this article.