How do various multifocal spectacle lenses differ?

Various multifocal lenses have areas of far and near vision (i.e. the upper and lower part) which are ground according to different eyes needs. Distortions caused by the lens structure appear on the edge area of multifocal lenses. Precise optical grinding enables to shift the location of the distortion, thus enlargening the area of either far or near vision. Larger near vision area is good for work at a closer distance. However, if it is more important to see far into the distance, then it is advisable to choose lenses with a larger far vision area.

The strength of multifocal lenses changes smoothly from the upper to the lower part which has the greatest closer strength. The transition area can be used for intermediate vision (e.g. 1-2 m). The main difference between multifocal lenses is how wide or long the transition area is and how well one can use its strengths for seeing.

Narrow and small frames need specially designed multifocal lenses which are ground so that the lower reading area is large enough.