The eye has a muscle called ciliary that allows to modify the thickness of the crystalline one, that is like a lens, in this modification it becomes possible to focus appropriately the vision and that forms the image just in the retina.

With the age this muscle loses contraction capacity and the proper crystalline one becomes less flexible and there appears the visual weariness or loss of capacity of accommodation for the nearby vision or long-sightedness.

The long-sightedness affects more precozmente to the long-sighted ones and to the persons with normal vision, but with the years it affects also the short-sighted persons.

The glasses of monofocal glasses are recommended to realize tasks of nearby vision for the long time consecutively.

The glasses with bifocal glasses allow to read closely and see of background without correction or with the one that was necessary earlier for myopia or farsightedness, these are recommended when it is needed to alternate between nearby and distant vision often.

The glasses with multifocal glasses allow the vision in both situations but esthetically they do not have the cut of bifocals, allowing the vision corrected closely and of background.

All the corrective glasses are necessary a time of adaptation, which in case of bifocal and multifocal is usually longer.

There are corrective contact lenses with all these systems, even with a correction for an eye to see closely and other of background.