Glaucoma Eye Test
Glaucoma is the name given to a group of diseases that cause damage to the optic nerve of the eye, leading to a loss of peripheral vision. The optic nerve connects the eye to the brain; information from the retina of the eye is passed along the optic nerve. The brain then processes this information and forms a picture of our surroundings.
Glaucoma rarely gives you any symptoms until it is very advanced, by which time it is often too late to treat effectively. Treatments currently available 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.
The 3 traditional checks for glaucoma are:
The pressure of the eye. We often check this with the air-puff test; you experience a small puff of air directed at your eye. The machine then calculates the pressure inside your eye based on your eye’s resistance to the air puff. It is painless but can make you jump a bit!If the pressure is higher than average we will recheck it on another day, as the pressure in your eye does go up and down.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.
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.
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 1 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 beginning of damage.
All of these tests have their limitations as highlighted above, and as such we are constantly looking at new ways to examine the eyes so we are obtaining as much information as possible. The OCT and GDx-VCC are new methods of examining the nerve fibres of the eye (which cannot be seen otherwise) and can identify problems earlier than a lot of the other tests. 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 than that.