Bifocal Contact Lenses
Bifocal Contact Lenses
How bifocal Contact lenses work
Certain designs should be added to the contact lens to enable the patient to see clearly for near and far and these designs are:
1- Translating design
This design of bifocal lens is also called segmented design or lens because it is divided into two segments. The upper segment is usually designed for far vision while the lower segment is designed for near vision.
When the patient is looking downward or working for near task, his eyes will move downward while the contact lens will move slightly upward and in this case the lower part of the contact lens or the near part will come infront the pupil and allows the patient to have near vision.
When the patient is looking for far distance like in driving, his eye will move to its position from the bottom to the top part and the contact lens will move from up to down, allowing the far distance to come infront the pupil and the patient can see for far.
It is also called alternating design because the pupil will alternate its position.
2- Simultaneous Bifocal Lens
In this type of Presbyopic Contact lenses, the patient will look for far and near distance at the same time .It has some difficulties at the beginning but with time, the eye and the brain will learn to choose the correct part of the lens for near or far and ignoring the other part.
Simultaneous Design consists of two types:
A- Aspheric Designs
Both near and far parts are designed at the center of the contact lens and your eye will learned how to ignore the other part when focusing in one part.
B- Concentric Designs
The center of this contact lens is for near and it is surrounded by multiple rings for intermediate and distance vision in multifocal lens or just one ring for far in bifocal lens.
The central part is not always for near vision, the center part can be for far distance while the peripheral parts for the near distance.
The locations of lens powers will change according to multi factors such as lifestyles, pupil size and type of contact lens.
Patient with small pupil will have better outcomes if the central part made for distance vision but patients with large pupil will have better outcomes if the central part made for near vision.
Soft contact lenses are usually with near part at the center while in hard contact lenses, the central part is usually for far distance.