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The Eye Examination
An eye examination should be an important part everyones regular health care. It is not just about determining wether you need glasses, it is also an important screening test for eye conditions such as glaucoma and cataract and also for general health issues such as diabetes and high blood pressure.
The eye examination will be carried out by an optometrist or an (ophthalmic) optician, they are different titles for the same qualification or by a doctor with a further qualification, an ophthalmic medical practitioner.
The first part of the examination relies on good communication, the optometrist will ask you some questions to try and find out why you have asked for a test and how they can help you. The optometrist will want to know if you wear spectacles, if you feel that they need changing or if you think that you might need them for the first time. He (or she) will also want to know if you are taking any medication or have any medical conditions, such as diabetes, as this can sometimes affect the eyes or increase the risk of some eye related problems. It is also important to know if anyone in your family has eye problems as they can also be passed down, glaucoma is more likely to occur if you parents suffered form it for instance.
You will also be asked about your job and hobbies. This is not just nosiness as the optometrist needs to know what strain you put on your eyes, do you drive for several hours at a time, do you work with a computer or are you finding it difficult to see your cross stitch etc.
The next stage of the test is to examine the eyes. This involves a thorough check of the health of both the internal and external eye. To look at the inside of the eye the optometrist uses an instrument called an ophthalmoscope. This is basically a torch and a very strong lens to focus through the lens in the eye. To do this properly it needs to be quite dark and the practitioner needs to come quite close to your face, if this causes you any distress please let him know and he will try not to eat garlic the night before!
The examination of the inside of the eye checks the health of the fundus
The next check is for glaucoma. There are two aspects to this, checking the pressure and measuring the sensitivity of the visual field. The pressure test can be carried out one of two ways, either by blowing a small puff of air at the eye or by putting a drop of anaesthetic and a drop of colour in the eye. Both tests work in the same way. Glaucoma is an increase in the pressure within the eye, when you pump up a bicycle tyre you squeeze it to see how hard it is, the higher the pressure the harder it is and the same is true in the eye the higher the pressure the harder the eye will be.
The other test that we use is a fields test. This measures the sensitivity of vision in the periphery. When glaucoma first starts to affect the vision it is in the periphery which makes it less noticeable than when it is in the centre of the vision. To check the sensitivity of the peripheral vision you will be asked to say how many little lights you see flashing or when you first see a light being brought in from the edge of your vision. Don't worry if you find this test difficult or think that you have missed some of the lights it does not necessarily mean that you have got glaucoma. The better you are at this test the harder the machine makes it to see the lights which gives an even better result but it means that everyone will miss some of the lights some of the time.
It is also important to check that the eyes are aligned with each other and that they move equally well in all directions.
The optometrist will measure what you can see with the unaided eye. This is done on the familiar letter chart which is 6 meters (20 feet) away. If you can read the standard vision line it is described as 20/20 vision (more commonly expressed as 6/6 nowadays).
The next stage is to asses wether you will need a pair of spectacles, again some of this is done in the dark, but it does allow the optometrist to objectively assess the prescription. Many people worry that they will give the wrong answer when they are asked if it is better with one lens or the other. Fortunately the optometrist will have some idea of which is likely to help and the question is only to confirm this. If the answer seems unsure or if it is inconsistent you will be shown the choice again, not necessarily straight away or in the same way as there may be ways to make the choices easier.
The optometrist will also check your vision at a normal reading distance and also at screen distance if you use a computer. Many people who play music find that the score is difficult to see because it is at an unusual distance and this can be corrected for with glasses as well.
After all these checks you will be given a copy of your glasses prescription (even if it says that you don't need glasses) and the optometrist will explain what it means and the best way of making the glasses, for instance are varifocals appropriate or do you need thinner lenses or would an anti-reflection coating work better for you.
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