Distance or short sight
The simplest form of spectacles is the single-vision lens, made to a single prescription to correct a particular eyesight problem.
Concave lenses, designed to correct short sight, are generally thinner in the centre than they are at the edge.
Convex lenses, designed to correct long sight, are usually thinner at the edge than at the centre.
The curvature of the lens, its thickness and weight will depend on the amount of long or short sight it is designed to correct.
The lens material will also influence the thickness and weight of your lenses, as will the size and shape of the spectacle frame you choose. Most lenses are now lightweight plastic and there is a wide range of materials available to suit your prescription and lifestyle.
There are three factors that influence lens thickness:
- The material used to make the lens
- Your prescription applied to the lens
- The frame size that the lens is going to fit
Choosing the optimum lens for your glasses is thus a complicated matter.
We give a little guidance to help you choose lens thicknesses for your prescription and we check your lens choice before we make your glasses. We will contact you if we feel that the lens you have chosen will not make perfect glasses.
This will mostly happen if either the sphere or cylinder of your prescription exceeds +- 4.00 but can occur at lower prescriptions. If the change required to your order is not significant, we will try to absorb the cost. In all cases we will e-mail you and let you know so you can decide if you want to proceed.
We offer lenses from a standard index of 1.5 through to ultra-thin index of 1.74. As a guide, and based on a standard plastic frame, we would suggest selecting the index below.
If you have a thin metal frame, to make your glasses look their best, we would suggest selecting a higher index lens.
- 1.5 index, if the sphere of your prescription is below +/- 2.50D
- 1.6 Index, (25% thinner and lighter) if your sphere is between +/- 2.50D to 5.00D
- 1.67 Index, (33% thinner and lighter) if your sphere is between +/- 5.00D to 7.00D
- 1.74 Index, (50% thinner and lighter) if your above +/- 7.00D
Pictorial comparison of our standard lenses and our extra thin lenses.