So you are thinking about getting your eyes tested. It’s not a bad idea. There’s so much more involved in an eye examination than checking to see whether you need new glasses.
Of course your sight will be tested and your prescription found. The prescription is just the strength of optical lenses that you see best with. It’s usually made up of three parts: sphere, cylinder and axis. The sphere is how long – or short sighted you are, the cylinder relates to how astigmatic you are and the axis just tells you where the astigmatism lies.
Short-sightedness (Myopia)
This is where things in the distance look blurred. It might be that you are struggling to read the programme menu on the television, find it hard to make out sign-posts when you are driving or have to peer to see a board at school or college. It may be that you are screwing up your eyes to see a little bit better. These are signs that you could be short sighted and could benefit from an eye test.
Long-Sightedness (Hypermetropia)
This is where your long distance vision is fine but your eyes are having to focus to keep things clear. This focusing ability is called accommodation. A lot of people are only slightly long-sighted and so it’s easy for them to focus without having any difficulty. Sometimes though the amount you need to accommodate is too much and either you develop eyestrain and you can end up with a headache, or your eyes don’t bother trying to focus and your vision is blurred.
When you come to read your eyes have to focus whether you have any prescription or not, so if you are a little bit long-sighted and then try to read, your eyes are having to first of all accommodate for the distance prescription and accommodate for the near. This can lead to your near vision being blurred.
Astigmatism
This is a slightly more complex visual problem. Here the front face of your eye is shaped like a rugby ball rather than a football, which means that there are different amounts of long or short-sighted in each main direction. It is very common. And most prescriptions have a small amount of astigmatism.
It’s unlikely that you would be aware that you were astigmatic without having a sight test, you would just notice that your vision is a bit blurred or that your eyes are getting tired looking at a computer screen or reading.
Presbyopia
This is where the lens inside your eye becomes harder with age and making it more difficult to accommodate and so close up vision becomes a bit more blurry and you have difficulty reading. This usually beings to happen around the age of forty.
As well as checking your prescription and advising on the need to get or upgrade glasses the optician will have a thorough check of the health of your eye. This involves examination with a slit-lamp and an ophthalmoscope, and an assessment of your visual fields.
The slit-lamp is usually mounted on a table which swings round and you’ll be asked to put your chin on a chin-rest and your forehead against a bar. Its like a microscope mounted on its side so the optician can see the structures of your eye under different magnifications. It is used primarily for examining the front of your eye but sometimes the optician introduce a Volk lens to let them see inside your eye. Its all rather bright for you and you can end up a bit dazzled.
When getting Ophthalmoscopy done you will be asked to look at a distant target while the optician is up very close to you shining another bright light in your eye. You’ll probably hear lots of clicks as the optician is changing focus from the front of your eye to the back.
If you are over sixty it is likely that the optician will want to use eye-drops to dilate (enlarge) your pupils. If you are getting this done its important that you don’t drive as your vision is affected by the drops. Its not that you can’t see once you’ve had them in, its just that your vision is a bit glary and distorted, especially if it’s a bright day. Its really worthwhile getting this done though, as it allows the optician to have a really good look inside your eye and allows them to take a photograph of the back of your eye.
Your visual field is the area that you see all round about you when you look straight ahead. This can be tested from just by covering on eye and the optician introducing objects from the side and moving them in till you can see them or using a machine that you look straight into and see flashing lights.
There are other tests involved in getting your eyes tested that the optician does according to your needs and presenting symptoms.
Even if you think everything is ok its always worth getting your eyes tested every two years, or every year if you are under16, over 60, diabetic or have glaucoma or are a close relative of a glaucoma patient.