There are 3 main types of vision impairment, myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. Surgical methods used in the treatment of these conditions are called Refractive Surgeries.
In healthy eyes, the light rays can be focused on the retina layer and there is clear vision. However in myopic eyes, light rays coming into the eye are erroneously focused on a closer point, not on the retina. This causes blurry vision, especially at a distance.
In hypermetropic eye, incoming light rays are erroneously focused on the back of the eye, not on the retina. This causes blurry vision, especially at close range.
In this condition, incoming light rays are erroneously focused in front of and behind the retina. This causes blurred distance and near vision.
When we are young, the natural lens acts like the zoom function in a camera, allowing us to focus up close, without the need for reading glasses or bifocals. As we age, the lens progressively becomes dysfunctional resulting in loss of near vision (presbyopia) that requires the use of reading glasses or bifocals.
Due to the advancement in technology and the safety of the procedure, some patients prefer to have their natural lenses replaced at an earlier age (age 40 – 60) rather than waiting for the age of cataract (age 60 – 75). Because of their active lifestyles, many patients do not want to have to tolerate the years of progressive decline in their vision as they develop cataracts; they want it fixed permanently now.
Nowadays, it is possible to get rid of near glasses with trifocal lens.
Additionally some people over the age of 40 may have both distance and near vision problems together. Trifocal lenses provide complete independence from glasses by solving both problem at the same time.