Editing Corrective lens (section)

=== Weight ===
Material density typically increases as lens thickness is reduced by increasing index. There is also a minimum lens thickness required to support the lens shape. These factors result in a thinner lens which is not lighter than the original. There are lens materials with lower density at higher index which can result in a truly lighter lens. These materials can be found in a material property table. Reducing frame lens size will give the most noticeable improvement in weight for a given material. Ways to reduce the weight and thickness of corrective lenses, in approximate order of importance are these:
* Choose glasses frames with small lenses; that is to say so that the longest measurement across the lens at any angle is as short as possible. This gives the greatest advantage of all.
* Choose a frame that allows the pupil to occupy the exact middle point of the lens.
* Choose a lens as near round as possible. These are less commonly found than other shapes.
* Choose as high a refractive index for the lens material as cost permits.

It is not always possible to follow the above points, because of the rarity of such frames, and the need for a more pleasing appearance. However, these are the main factors to consider if ever it should become necessary and possible to do so.