If you are over 40 and have difficulty seeing close up, you probably have a common age-related condition called presbyopia. Presbyopia occurs when the eye’s natural lens loses the ability to focus on close objects. It is a natural process of aging. Individuals with presbyopia are familiar with the need to hold reading materials at arm’s length in order to see clearly, yet can see clearly with reading glasses or bifocal/progressive lenses.
Fortunately for those who don’t like the look, feel or inconvenience of reading glasses, there is another option. Bifocal and multifocal lenses are also available in contact lenses in both soft and Rigid Gas Permeable (RGP) varieties.
Multifocal contact lenses are generally designed in one of two ways, as either simultaneous vision lenses or alternating vision lenses.
Soft Contact Lens Multifocals
Soft multifocal lenses are available in a simultaneous vision lens design. These lenses present the distance and near vision zones of the lens at the same time. Typically after a short adjustment period, your eyes learn to utilize the segment of the lens that they need to focus on the desired object and essentially ignore the other.
There are two types of simultaneous lens designs available:
- Concentric ring design: In the most basic form these are bifocal lenses that are comprised of a central circular area of one power with a ring around of the alternate power, similar to a bulls-eye. The width of each ring is variable depending on the power that is needed most and the edges of the rings can be blended for a smooth transition of focus, similar to progressive eyeglass lenses.
- Aspheric design: These multifocal lenses attempt to provide a natural vision experience by blending many lens powers across the surface and center of the lens. In this design both distance and near vision power are located in the central visual area and your eyes will adapt to focus on the area needed to view what you are looking at.
Rigid Gas Permeable Multifocals
Translating or alternating vision lenses are similar to bifocal eyeglasses, these contacts are divided into distinct areas or zones and your pupil will move to the desired zone depending on your vision needs. The top of the lens, which is what you look through when looking straight ahead is for distance vision and the bottom area (what you look through when you look down) is for near vision.
Since contact lenses sometimes move within your eye, translating lenses are held in place by a ballast which is an area that is thicker than the rest of the lens or by truncating or flattening the bottom to stay in line by the lower lid. These lenses are only available in rigid gas permeable lens material.
An Alternative Option to Multifocal Contact Lenses: Monovision
Monovision is another contact lens alternative for presbyopia particularly if you have difficulty adapting to multifocal lenses. Monovision splits your distance and near vision between your eyes, using your dominant eye for distance vision and your non-dominant eye for near vision.
Typically you will use single vision lenses in each eye, however, sometimes the dominant eye will use a single vision lens while a multifocal lens will be used in the other eye for intermediate and near vision. This is called modified monovision. Your doctor will perform a test to determine which type of lens is best suited for each eye and optimal vision.