Glaucoma is the name given to diseases that cause damage to the optic nerve of the eye. This can lead to a loss of peripheral vision. The optic nerve connects the eye to the brain and information from the retina is passed along it. The brain then processes this information and forms a picture of our surroundings.
The problem is that Glaucoma rarely gives you any symptoms until it is very advanced, by which time it is often too late to treat effectively. Treatments will not reverse any damage that has already been caused, but can prevent any further damage occurring. It is therefore very important that glaucoma is picked up as early as possible to allow for more effective treatment. This is part of the reason why regular eye examinations are so important, even if you feel your vision has not changed in any way.
The 3 traditional checks for glaucoma are:
1. The pressure of the eye
We will nearly always check this if you are over 40, regardless of family history. We do NOT use the machine that puffs air at your eye. Instead we prefer the more accurate method using an called a Goldmann Tonometer. For this we put some numbing, yellow drops in the eyes, then the Goldmann Tonometer sits gently on the front surface of your eye. It is painless, very quick, and more accurate than the air puff.
The pressure test has its limitations as different people will have different eye pressures – some people will have a higher than average pressure but will not develop glaucoma. Equally, some people will have a pressure that is within normal limits but they will go on to develop glaucoma.
2. The visual fields test
This is a test of your peripheral vision. We will ask you to sit looking into a machine with a button in your hand. You will see little dots of light flashing in the machine one at a time and you click the button every time you see a dot of light. It sounds simple but can be a little tricky as you are not allowed to move your eyes to follow or look for the dots. Also, a lot of the lights are very dim so it can sometimes be difficult to tell whether you did see a light or not.
It is not unusual for the results to be less-than-perfect even if the eyes are healthy - it's just not an easy test to do, so if the results don't seem quite right we often ask you to come in on another day to repeat it. If we get the same results again this may suggest the beginnings of glaucoma (although it can also identify other problems).
There may be as much as 40% of the nerve already damaged before it will show up on a visual fields test.
3. The appearance of the optic disc
This is the top of the optic nerve at the back of the eye. This nerve is made up of over a million nerve fibres which are very thin and are not visible to the naked eye. The optic disc does not look the same in everyone's eyes which can make it very tricky to identify problems just by looking at it, but there are certain signs that we look for that can indicate the presence of any damage. We use a Topcon NW6s fundus camera to store images of your retina and optic disc. These images are very helpful in detecting any changes over time.
All of these tests have their limitations and as such we are constantly looking at new ways to examine the eyes so we are obtaining as much information as possible. No one test will tell us for sure whether you have glaucoma or not but by doing a range of different tests and collating the results we can more effectively identify glaucoma in its earlier stages.
Even more importantly, make sure you stay up to date with your eye examinations as this is the best and most effective way to identify if things are changing. We generally recommend an eye examination every two years but if there is a history of glaucoma in your family (particularly a first degree relative such as a parent or sibling), or if there are signs that glaucoma may be developing, we will monitor you more closely.