If you want to purchase cheap specs online then make sure you understand one or two essentials before you start. It is true that you are now uniquely able to dramatically reduce how much you have to spend so long as you know how to buy your glasses wisely and it they will be perfectly good for you to use so long as you become cognisant of a few simple rules
Make certain that your new spectacles will fit well
If your current specs fit fine, then take your time in measuring your old glasses and you will get perfectly fitting new specs online.
You need to know a few measures:
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Make sure that you measure the total width (A) properly. You can get your new on-line eyeglasses to fit perfectly well as long as long as you have the total width, even if you get the lens height or width slightly wrong.
Ensure that you have the precise lens prescription
There are just four parameters of your prescription that you will need to note:
- Sphere - This is the measure of severity of you near or far sightedness. This value specifies the optical power of a lens in diopters. It invariably will have a positive (+) or a negative (-) symbol in front or above it.
- Axis - This will only appear if there is a value for cylinder, as it relates to the cylindrical lens and denotes a reference point that indicates the direction of the power of the cylindrical lens. The value will be a number between 1 and 180.
- Cylinder - This refers to the degree of astigmatism that you possess. Again, there is always a plus (+) or minus (-) sign around. You could find that your prescription does not have a cylinder value, if you don’t have an astigmatism.
- Pupillary Distance (PD) - This measurement is used to accurately center the lenses in the frame that you have selected. Technically, PD is the measurement of the distance between the centre of your pupils.