This is a short description of different types of contact lenses. Your optometrist or optician, who knows your eyes, will provide you with more information for your individual eyes. Note that contact lenses for presbyopia have the advantage that no spectacle lenses are required for near vision. However, for physical reasons the quality of vision with these contact lenses will not reach the quality of single near vision spectacle lenses. In any case, the wearer of contact lenses should try whether these solutions are comfortable and provide sufficiently clear vision for the individual needs.
First of all, eyes wearing contact lenses need to be well supported with oxygen and moisture for which frequent blinking is important. However, blinking is often automatically suppressed during continuously focussing and attention to the monitor. So it may help to blink consciously or to close the eyes from time to time.
* Hint *: Attach a little note at the side of your monitor indicating “Blink!” which reminds you to sometimes interrupt your task for a few seconds in order to blink a few times.
1. Single vision contact lenses
Single vision contact lenses improve far vision, in cases of myopia (near sightedness, negative lenses) or hyperopia (far sightedness, positive lenses). Additionally, astigmatism can be corrected (when a point appears as a small line due to a non-symmetrical cornea).
2. Bifocal contact lenses
Bifocal contact lenses improve far vision in cases of myopia (near sightedness, negative lenses) or hyperopia (far sightedness, positive lenses). Additionally, astigmatism can be corrected (if a point appears as a small line due to a non-symmetrical cornea). Most important, near vision is improved in cases of presbyopia.
One type of bifocal contact lenses resembles bifocal spectacle lenses (see above). If the eyes are inclined downward, these contact lenses are shifted higher on the eye ball. The lower part of the bifocal contact lens with the additional optical power for near vision is shifted in front of the pupil for clear near vision.
Other types of bifocal contact lenses include two concentric zones, one for far vision and one for near vision. Accordingly, two images are superimposed onto the retina at the same time. Thus, one image is sharper than the other and the brain needs to extract the sharper one. The individual user may try whether this solution is comfortable.
- 3. Multifocal contact lenses
For presbyopia, these lenses include several concentric zones with several amounts of optical power corresponding to different viewing distances. The brain will extract the sharpest image of the several images that are projected onto the retina.