Multifocal Contact Lenses
Are you over 40? If so, you may want to consider wearing multifocal contact lenses.
You're probably much more active than your parents were at your age. Biking, jogging, exercising and playing sports are just a few of the activities that today's 40-somethings routinely enjoy.
So it's no surprise that many people 40 and older prefer contact lenses over glasses for their active lifestyles.
Once we reach our mid-40s, presbyopia makes it difficult to focus on near objects. Reading glasses used to be the only option available to contact lens wearers who wanted to read a menu or do other everyday tasks that require good near vision.
But today, a number of multifocal contact lens options are available for you to consider. Multifocal contact lenses offer the best of both worlds: no glasses, along with good near and distance vision.
Some multifocal contact lenses have a bifocal design with two distinct lens powers one for your distance vision and one for near. Others have a multifocal design somewhat like progressive eyeglass lenses, with a gradual change in lens power for a natural visual transition from distance to closeup.
Multifocal contacts are available in both soft and rigid gas permeable (RGP or GP) lens materials and are designed for daily wear or extended (overnight) wear. Soft multifocal lenses can be comfortably worn on a part-time basis, so they're great for weekends and other occasions if you prefer not to wear them on an all-day, every day schedule.
For the ultimate in convenience, one-day disposable soft multifocal lenses allow you to discard the lenses at the end of a single day of wear, so there's no hassle with lens care.
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In some cases, GP multifocal contact lenses provide sharper vision than soft multifocals. But because of their rigid nature, GP multifocal contacts require some adaptation and are more comfortable if you condition your eyes by wearing the lenses every day.
Hybrid multifocal contacts are an exciting new alternative. These lenses have a GP center and a soft periphery, making it easier to adapt.
A commonly used contact lens design for people with presbyopia is the concentric bifocal pattern. In this type of contact lens, the near correction is in a small circle at the center of the lens, surrounded by a much larger circle containing the distance correction. The distance correction could be placed in the center instead, with the near prescription in the outer ring.
Beyond this familiar configuration, the two basic multifocal contact lens designs are alternating and simultaneous image.
Alternating image designs (also called translating designs) have distinct zones in the lens for distance vision and near vision. These designs are available in gas permeable lens materials only.
Like bifocal glasses, the top part of an alternating image multifocal GP lens is for distance vision and the bottom part is for near. The two zones are separated by a nearly invisible line that helps your eye care professional determine if the lens is fitting properly.
When you look straight ahead while wearing an alternating multifocal, you're looking through the distance portion of the GP lens. When you look down to read, the lens remains supported by your lower lid, so your line of sight now passes through the lower (near vision) portion of the lens.
(If you can't see the video, you may need Flash Player.)
The near segment can have a half-moon, crescent or annular shape. (The annular segment circles around the entire periphery of the lens.)
In alternating multifocals with half-moon or crescent-shaped near segments, the lens maintains its proper rotational position by means of an area of unequal thickness in the lens called a prism ballast. In some cases, the bottom edge of the lens is also truncated to help align it properly with the wearer's lower lid.
Because alternating multifocal lenses typically have just two lens powers, these lenses usually provide good vision for driving and for reading. But they may not perform as well as simultaneous image designs for computer work and other intermediate-range visual tasks.
Simultaneous image designs have both distance and near vision portions of the lens in front of the pupil at the same time. These designs are available in both soft and GP lens materials.
Your brain must determine which area of the lens to emphasize and which area to ignore to provide the best image resolution.
Blended designs, such as the aspheric example shown here, can be complicated because they seek to correct the particular points of aberration in your eyes, to provide the most natural vision experience possible.
Left: In this example of a translating design the near power is on the bottom. The bottom edge is flattened to keep the lens from rotating on your eye when you blink. Middle: In this concentric design the near prescription is in the middle and far is on the outside, but they can be reversed. Right: In this aspheric design the near and distance prescriptions are both near the pupil.
In the past, soft multifocal contact lenses could not correct astigmatism. If you had astigmatism, your only choice in multifocal contact lenses was rigid gas permeable lenses.
Today, soft multifocal contacts can also correct astigmatism by using a toric lens design. The lenses achieve the proper rotational positioning on the eye by means of unequal thickness zones in the lens to create a prism ballast effect (similar to that on a translating GP multifocal).
Hybrid multifocal contact lenses also correct most types of astigmatism.
Until you have a contact lens fitting, there's no way to know for sure if you'll be able to successfully adapt to wearing multifocal contact lenses. If multifocal lenses aren't comfortable or don't give you adequate vision, a monovision contact lens fitting may be a good alternative.
Monovision uses your dominant eye for distance vision and the non-dominant eye for near vision. Right-handed people tend to be right-eye dominant and left-handed folks left-eye dominant. But your eye care professional will perform testing to make that determination.
Usually, single vision contact lenses are used for monovision. One advantage here is that single vision lenses are less costly to replace, lowering your annual contact lens expenses.
But in some cases, better results can be achieved using a single vision lens on the dominant eye for distance vision and a multifocal lens on the other eye for intermediate and near vision.
Other times, your eye care professional may choose a distance-biased multifocal on your dominant eye and a near-biased multifocal on the other eye. These techniques are referred to as modified monovision fits.
What if Multifocal Contacts Don't Work Out?
If your multifocal contact lenses don't work out for you, your eye care professional can return most brands to the manufacturer for a refund. So if you're an unsuccessful wearer, you can usually receive a full or partial refund of the material costs of your contact lens fitting fee.
But part of your contact lens fitting fee involves the time and services your eye doctor or contact lens fitter provides during the fitting and follow-up visits. This portion of your overall fitting fee usually is not refundable.
To increase your chances of success with multifocal contact lenses, it's important to manage your expectations. These lenses usually won't be able to match the clarity you get with bifocal or progressive eyeglass lenses. It's also very likely you will still need single vision eyeglasses or reading glasses for specific tasks like driving at night or reading small print.
But it's reasonable to expect multifocal contact lenses to give you very acceptable vision for 80 percent of your daily activities, and without the need for supplemental eyeglasses.
About the Author: Gary Heiting, OD, is senior editor of AllAboutVision.com. Dr. Heiting has more than 25 years of experience as an eye care provider, health educator and consultant to the eyewear industry. His special interests include contact lenses, nutrition and preventive vision care. Connect with Dr. Heiting via Google+.
Original version of this article was by Liz DeFranco, ABOC, NCLC.
[Page updated February 2010]
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