Do I need High Index Lenses for my Prescription?

Do I need High Index Lenses for my Prescription?

So how do you know whether you need High Index Lenses? To answer this question you will need to take a look at your prescription.  At first glance, it may look a little complicated but we will try to explain what each of the columns represent. The good news is that no matter which part of the world you have your eyes tested in, all prescriptions are written in an industry standard format. 


The right eye (sometimes written as O.D) is always shown first, followed by the values for the left eye (sometimes written as O.S). Essentially there are 4 columns that we need to understand…

Sphere (SPH): This is the power required to correct your vision, If this is a minus value (–) then you are short sighted. If this is a plus value (+) then you are long sighted.

Cylinder (CYL): This tells you if you have any astigmatism in your prescription.  Astigmatism is quite a common condition and occurs when the cornea becomes elongated. This effects the way light passes through the cornea and causes distortions to your vision. The CYL value can be either a plus (+) or a minus (-) value. 

Axis: If there is a value in the (CYL) column as described above, then the Axis value will be a number between 0 and 180. This shows how many degrees the lens needs to be turned in order to correct the astigmatism. Note: If there is no astigmatism then both the CYL and Axis values will be blank.

Addition (Add or Near Add):  If there is a value in this column then an additional correction is required for reading. It will be needed where separate reading glasses are required or for making up bi-focal or varifocal lenses, which have both the distance and near correction powers. This will always be a plus (+) value.

Generally speaking, if you have a value higher than (+) 2 or (–) 2 in either the SPH or CYL columns, then you should definitely consider High Index Lenses. The higher these values are, the more complex your prescription is. High Index Lenses are thinner and lighter than standard lenses, so they benefit those of us with strong or complex prescriptions. High Index Lenses are available in a variety of indexes which start at 1.61 index and go all the way up to 1.9 index. The higher the index, the thinner your lenses will turn out. High index lenses are advantageous whether you are long or short sighted as they will improve the overall appearance of your glasses. Not only will they help with the aesthetic look but they will also be lighter in weight than standard lenses.

It is important to choose the right High Index Lenses as this will determine the overall thickness of your glasses.  There are essentially three types of High Index lenses to choose from, Plastic High Index Lenses, Glass High Index Lenses and Double Aspheric (Bi Aspheric) Lenses. There are pros and cons to each lens type but the options available to you will be determined mainly by your prescription and also what you want to use your glasses for. For more information click here.

If you need any help choosing the right High Index Lenses for your prescription then contact our customer service team on 020 8150 3484 or


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