Two of the most common contact lens prescriptions prescribed for people today are for the eye conditions of presbyopia and astigmatism.
Modern technology has made bifocal and toric contact lens designs available in both the rigid gas permeable (RGP) lenses and the soft lenses, offering more options and wear schedules then ever before.
Only a small percentage of people prefer the rigid gas permeable lenses to the soft contacts. The reason being that the RGP lenses retain their shape over the cornea more successfully than do the soft lenses, and are said to provide crisper vision to people with the eye condition astigmatism. However the majority of people prefer the soft lenses as they come in more choices and take less time to adjust to .
Presbyopia is a condition that occurs as the eye's lens grows older and starts to lose some of its elasticity, which is needed to switch focus between viewing near and far objects. About one hundred million Americans experience this common eye condition.
Presbyopia affects most people between the ages of forty and fifty, and is a natural part of the aging process. Once presbyopia begins, your vision will continue to change, so that regular eye exams by your eyecare practitioner will be a part of life. As your eye's lens loses more elasticity, the eye will take longer to adjust between objects, an example being between the road and the speedometer.
Bifocal eyeglasses used to be the only option for people with the condition, but today there are many bifocal contact lenses in a variety of convenient and comfortable designs.
The most obvious sign that you're developing presbyopia is the need to hold any reading material, like the newspaper or a book, further away from you eyes in order focus and see clearly.
The way bifocal contact lenses work is very similar to bifocal eyeglasses. The contacts have two separate powers on one lens; one to correct distance vision and the other to correct near vision if this is the prescription that is needed. There are a couple of different design options for the bifocal lenses.
One of the designs works similar to how the bifocal eyeglasses work with two obvious prescriptions separated with a line (the distance vision on the top and the near vision at the bottom). The other design works somewhat like a progressive eyeglass lens, having the two different prescriptive powers blended on different parts of the lens, forcing your eyes to learn to differentiate the correct power for the correct distance.
The wonderful thing about bifocal contact lenses is the convenience they offer. Contact lenses are so thinly designed that the wearer doesn't even know they are there.
Contact lenses eliminate the barriers that eyeglasses provide with the line of vision from below, above and the sides of the eyes, allowing for great peripheral vision with the hassle and image distortion sometimes cause by bifocal eyeglasses.
There are three different designs for the bifocal contact lenses, concentric, simultaneous and alternating vision.
The concentric designed lenses have one power centered in the lens and the other surrounding it, for example the distance power may be in the center of the lens with the near power surrounding it, or the other way around.
The simultaneous vision lenses contain both the near and distance prescriptions centered on the pupil, your eyes learn to adjust to the proper power depending on what your looking and focusing on. Lastly the alternating vision works similar to the bifocal lenses separated by a line with one power at the top of the lens and the other power at the bottom.
There are people who have difficulty adjusting to the bifocal contact lenses and for this reason they may not be the lenses for some people. It does take time for the eye to adjust to the two different powers within the lenses, with exactly how much time to adjust varying from person to person. It's important not to give up right away and give the lenses a chance, as some people take longer than others to get used to the lenses.
If however you are unable to see clearly with the lenses, your eyecare practitioner may recommend the monovision lenses. With these particular lenses, one contact is worn with one power to correct the distance vision with the other lens correcting the near vision.
Some people adapt to these lenses immediately. If having to wear bifocal lenses for the first time and your concerned about what will work best, your eyecare practitioner may have some free-trial programs in place allowing you to try out different lenses before deciding on a particular pair.
Astigmatism is the most common of vision problems, and may be accompanied by nearsightedness (hyperopia) or farsightedness (myopia).
The cause of astigmatism is an irregularly shaped cornea, which can be corrected with toric contact lenses. Until recently soft contact lenses were not available for astigmatism correction, but fortunately toric contact lenses are now made in disposable, frequent replacement, multifocal and colored lenses (there may be some complex prescriptions that are not available in the soft lenses). Toric contact lenses come in both soft and rigid gas permeable (RGP) designs.
Toric lenses are created with two powers in them, one for astigmatism and the other for myopia or hyperopia.
Toric lenses contain a ballast system (bottom of lens is thicker), which keeps the contact in one position. The cost of toric contact lenses is more expensive than regular contact lenses, as the fitting procedure for torics is more extensive; the lenses are also more expensive than regular lenses.
Toric contact lenses come in many options, your eyecare practitioner will help you select the lenses with the best compatibility for your specific eyes. Multifocal toric contacts offer correction for presbyopia and astigmatism; these lenses are available in soft and RGP varieties, the rigid gas permeable lenses being the recommended of the two.
Contact lenses are a convenient and healthy way to treat your eye vision problems. Both presbyopia and astigmatism correction can be easily achieved with a small adjustment period, without the inconvenience of eyeglasses. A visit to your eyecare practitioner can assist you with the lens choice and replacement schedule best suited for you.
Also see our article How to Put in and Care for Contact Lenses
Have Your Say:
We welcome relevant discussions, criticism and your unique insights. Comments are moderated and will not appear until approved. NOTE: We do not verify information posted in the comment section.