|Varifocal glasses, also known as the progressive glasses, graduated glasses and no-lines bifocals are generally used to correct presbyopia and have become one of the most used glasses for prescription as well as designer glasses. The name comes from the fact that the glasses have different power at different levels of the lens. At the top of the lens, the power is minimum, which gradually increases in the middle level and finally, the bottom part of the lens has the maximum power.
It is widely regarded, that the world’s first commercially available varifocal glasses was developed by Duke Elder in 1922 and was subsequently sold by “Gowlland of Montreal”. In 1953, Bernand Maitenaz developed the first modern varifocal lens: The Varilux, which was introduced by the Société des Lunetiers (which later became a part of Essilor).
The greatest advantage of varifocal glasses is the ability to look at objects at varying distances with just a slight tilt of head. As the different levels have different powers, the top part can be used to view objects at a distance, the middle one at the objects at an intermediate distance and the bottom part while working on nearby objects, like reading a book. They also avoid the discontinuities like image - jumps which occur in the visual fields created by bifocal and trifocal glasses. Commercially, varifocal glasses are quite popular too, because of the absence of any line on the lens.
The primary problem with the varifocal lens is its requirement of a careful placement which is related to the user’s pupil centre to generate a distance – viewing reference position. Incorrect specification of this location can cause serious problems which include narrow fields of vision or even clear vision in only one eye. The need to adapt to uncomfortable head positions may also arise, which is unhealthy and risky to the entire body.
Finally, it takes time to adjust to varifocal lens. It may range from few hours to almost two weeks. During this adapting phase, side effects generally include headaches and dizziness.