Eye care
What is your prescription
There are usually two components to any eyewear prescription.
You are either nearsighted, which means you can see at near but not at a distance, or farsighted, which means the opposite.
About 70% of eyeglass wearers also have some form of astigmatism. This simply means that the front part of the eye, the cornea, has 2 different curvatures (like a football). So lenses are designed with two different curves to compensate for the shape of the eye to correct the astigmatism.
Here's an example of an eyeglass prescription:
OD -3.00/-1.50 X 180
OS +2.50/-1.00 X 165
This is what it means.
OD is a latin abbreviation for the right eye.
OS is a latin abbreviation for the left eye.
The first number (-3.00 in the example) is called the sphere. This tells the optician what power to make the lens to correct the nearsightedness ( - ) or farsightedness ( + ). In our example the right eye (OD) is nearsighted and the left eye (OS) is farsighted.
The numbers after the ( / ) refer to the amount of astigmatism. The ( X ) is an abbreviation for the word 'axis' and the numbers 180 and 165 indicate the placement in degrees of the astigmatic lens.
THE NUMBERS THAT CONCERN YOU WHEN DECIDING THE BEST SIZE FRAME FOR YOUR PRESCRIPTION ARE THE SPHERE NUMBERS (-3.00 and +2.50 in our example).
If your prescription is less than -2.50 or +2.50 almost any size and shape frame will be suitable for your prescription. You do not require hi-index or thin and light prescription lenses. Any frame with regular plastic lenses will have an acceptable edge thickness and should look cosmetically pleasing to you.
For prescriptions of -2.50 to -4.00 you should choose a frame with an eye size of 54 or less. The size is written on the inside arm of the frame. If you have to have a frame with a larger size because of style or face shape, then make sure you get hi-index or the thin and light lens. Otherwise, your lenses will have thick edges.
Do not choose a rimless frame if your prescription is over -2.50 unless you use a high index lens, or edge thickness of the lens will be a problem.
For prescriptions of -4.00 to -6.00 it is advisable to order your lenses in a hi-index material and to keep the frame size as small as possible. This will ensure that your glasses look the thinnest.