All you want to know about Eye Tests and Results
What happens in a regular eye test to check spectacle numbers?Top eye hospitals often have an optometrist to first have a look at your eye. First, a complete history is sought. You are asked questions about what complaints brought you for an eye check, other illnesses (to find out if diseases like diabetes or high blood pressure could have a toll on your eyesight), the medications that you have been taking (some medicines may have an effect on your eyes in the long term), eye diseases that run in your family, the nature of your profession and few details of your lifestyle that could affect your sight like the number of hours spent at the computer, time spent in the sun etc.
Next, you will be checked for distance vision. This is done by asking you to look at a chart with alphabets of various sizes and identifying the smallest size that you can see clearly.
After that you are tested for near vision. A small hand held card with text of various sizes is held about 12-14 inches from your eyes.
Regular spectacle users who seek eye care in top eye hospitals are probably very well aware of all this. They often have questions about the prescription that is handed after the test: What do the numbers indicate? What do + and - mean? Patients are often left wondering what the codes on the prescription means. Even if it's one of the top eye hospitals, very few patients receive answers to their queries.
Eye Vision Test can be done by your doctor or optometrist to determine whether you need a less or more corrective glasses or lenses. New prescribed glasses or lenses will be made according to your test result.
Usually the doctor will do simple test to check your eyes as follow:
1. Retinoscopy. It is usually the first eye exam that doctor will give you to make approximation of your prescription.
2. Refraction. During this test, doctor will be able to determine your exact prescription by using phoropter in front of your eyes and shows you series of lenses choices. Here you can find the right combination of lenses which can make you see clearly.
3. Autorefractors and aberrometers. With this test, your doctor can automatically determine your prescription. Your chin need to rest stable on both devises while you look at a pinpoint of light or other image.
4. Cover test. This is the simplest and the most common test among the others to determine how your eyes work together.
5. Slit-lamp examination. It is also called a biomicroscope which allows the doctor to gain magnified image of the structures of the eyes in order to thoroughly evaluates them for the sign of disease of infection,
6. Glaucoma test.
7. Visual field testing.
Understanding the test results:The results of far vision testing are recorded as a fraction. While 6/6 is considered normal, a vision of 6/9 would mean that you can see at 6 metres what a normal person would be able to see at 9 metres. The results of near vision testing are expressed as N6, N8, N10, N14 etc. and N6 is considered normal.
The other components:
- SPH / Sphere: This records if you are short sighted (- minus sign) or long sighted (+ plus sign) and by how much.
- CYL / Cylinder: This means that your eyes are not perfectly spherical and you have astigmatism.
- AXIS: This indicates the orientation of the astigmatism.
Apart from the above vision testing, additional tests may be needed to test your peripheral vision, colour vision, depth perception, eye muscle balance, eye pressure, retina (the back of your eye) etc. Top eye hospitals usually offer all these services under one roof which means that you need not worry about anything other than... just getting yourself to seek the elusive time for that appointment!
By Dr. Amrita Sodhi