What causes glaucoma and how is it diagnosed?

Glaucoma is a condition that damages the optic nerve, which if left untreated can lead to a loss of vision. Mr Vik Sharma, an expert ophthalmologist, explains what causes glaucoma and how it is diagnosed.

What is glaucoma?

Glaucoma is a condition of the optic nerve, the nerve at the back of your eye that sends your vision to your brain. Traditionally, we always thought of glaucoma as high-pressure - the pressure in the eye being too high and then damaging the optic nerve and causing you to lose your sight. We have recently learned that although pressure plays a role, it does not necessarily have to be high in the abnormal range to cause damage. If it is too high for your eyes then we need to lower the pressure and we know that lowering the pressure lowers the risk of you developing glaucoma, so it is very important that you get your eye pressure checked to make sure your eye nerves stay healthy.

What causes glaucoma?

Glaucoma is caused by many factors, some of which are unknown. The biggest factor for glaucoma is the pressure in the eye - the intraocular pressure. That is the one single factor that we can try to treat and control and that is how we manage glaucoma by keeping the pressure down. There is a genetic component to glaucoma as well, so if you have a family history of glaucoma you are much more likely to develop the disease. Also, people with certain conditions, such as diabetes or short-sightedness, are more likely to get glaucoma. 

How is glaucoma diagnosed?

We diagnose glaucoma traditionally by checking three important items. The first being the intraocular pressure – we must check the eye pressure to ensure it is normal. If it is high, then that increases your risk of developing glaucoma. The second thing we look at is the visual field, looking at the peripheral field of vision, and traditionally, that test is done on each individual eye separately and it maps out your field of vision and tells us if there is anything going on that needs treatment. Normally, glaucoma affects your peripheral vision before it affects your central vision so we do need to test the peripheral vision. Then most importantly, we need to look at the optic nerve at the back of your eye in detail. The optic nerve gets damaged from the pressure which will make it thinner, and cause a loss of nerve axon fibres. It is important that we detect these changes in the optic nerve and treat them so that they do not worsen.

We now have scanners that can scan your nerve and look at the invisible layers and tell us exactly what is going on with the optic nerve and before we can even see a thing, the scanner will pick it up and tell us your risks and it will actually look at your nerve and compare it to a healthy individual of the same age. We also have measurements of the wall of the eye to make sure that your wall is not thin, which is an independent risk factor for glaucoma. In addition, we have little tools that we use nowadays to look within the eye, looking at the drainage system so we can accurately assess it and look and see whether there is any blockage going on, for example. 

Can you go blind from glaucoma?

The short answer to whether you can go blind from glaucoma is yes, but I do not want to scare anybody and the facts are that over 90% of people with glaucoma will not go blind. There is a small percentage of people who go blind; about 5% in this country, and about 10% of people get functional, visual problems but they maintain some vision. The vast majority of people live a normal, healthy life with no problems with their vision, providing they are caught, detected and treated appropriately. The people that go blind and the people that are not caught in time are the people who do not get their eyes checked regularly for glaucoma. They are the ones that are at a higher risk of going blind. Hence, it is really important that everybody gets their eyes checked, particularly as we get older. 

If you would like to find out more, make an appointment with a specialist.