Which Bifocal Design Is Right for You?
Are you ready to try bifocal contact lenses but don't know what your options are? Here are some common lens designs and fitting strategies, with information on who is a good candidate for each one.
Bifocal vs Multifocal: What’s the Difference?
Multifocal lenses focus at a variety of distances. Bifocal lenses are a type of multifocal lens, but focus at only two distances, usually far and near.
Aspheric Designs
In aspheric multifocal contact lenses, the curve of the lens gradually changes from its center to the edge. This creates a gradual change in lens strength from far to near distances. These different focal points all enter the pupil, or opening of the eye, at the same time. The brain pays attention to the optics it is interested in. For example, when gazing at something far away, your eyes learn to ignore near objects; when focusing near, your eyes learn to ignore far-off objects. Whereas some bifocal designs require one to look down to see at close distances, aspheric designs allow you to see at far and near distances in any direction.
Concentric Designs
Concentric lenses (also called annular lenses) use a bulls-eye pattern. The near prescription may be in the middle of the bulls-eye, with distance correction in the outer ring, or vice-versa. The placement of the prescriptions depends on your particular lifestyle and activities.
If you need an intermediate prescription for viewing 18 to 24 inches away (such as when you work at a computer), an extra ring may be placed between the other two, creating a multifocal contact lens. The widths of the rings may vary, to emphasize a particular vision need. Often the intermediate and far prescriptions are blended together at their edges, for a smooth transition from one to the next that is similar to wearing progressive eyeglass lenses.
Combination Designs
Both aspheric and concentric designs work well for people who are just beginning to experience presbyopia, since their near prescriptions are usually not very strong. Many of today’s designs combine an aspheric curve on the back surface with a concentric design on the front surface to provide a lens with a stronger reading prescription.
Translating Designs
In translating bifocal lenses, the top of the lens generally provides correction for viewing objects far away while the bottom of the lens provides correction for near tasks. Sometimes a third area is incorporated between these two to correct for arms length distance. Since this design corrects for three different distances it is referred to as a trifocal.
In order to keep the correction for near distance oriented toward the lower eyelid to allow for reading in down gaze, these lenses are weighted. They may also be flattened (or "truncated") at the bottom, so the lower lid will support and shift the lens upward when the pupil needs to line up with the near vision zone. Due to the supporting function of the lower eyelid it is important that it not be droopy.
Translating designs can provide excellent vision and work well whether you need a weak or a strong near prescription. However, near vision is generally only provided while looking down. If your upper eyelids have begun to droop (this is caused by a weakening of the muscle and occurs as we age), they may interact with translating lenses too much, and a different design may work better.
Translating lenses must be able to move freely on the eye in order to re-center after a blink. Translating lenses can accommodate large pupils, though not as easily as smaller pupils.
Monovision: An Alternative to Bifocals
In a monovision fit, usually one contact lens corrects for far viewing while the other corrects for near viewing. The brain learns to pay attention to the eye that provides vision for the distance of interest. For example, while driving your brain pays attention to the eye providing correction for far viewing while ignoring the eye providing correction for near viewing.
Modified monovision may describe one of three scenarios:
- describes a lens that corrects for a single distance, referred to as a single vision lens, is in one eye and a bifocal lens is in the other eye
- a bifocal lens in each eye, each with different near vision powers
- a multifocal lens in each eye, but one has a zone for distance viewing in the center and the other has a zone for near viewing in the center
Frequently Asked Questions About Multifocal Contact Lenses
We've compiled some of the most frequently asked questions about multifocal and bifocal contact lenses. Click a question for the answer.
Q. What’s the difference between multifocal and bifocal contact lenses?
A. Multifocal lenses focus at a variety of distances. Bifocal lenses are a type of multifocal lens, but focus at only two distances, usually far and near.
Q. Who can wear multifocal or bifocal contact lenses?
A. You're an especially good candidate if you are already used to wearing contact lenses or if you have already adapted to bifocal, trifocal, or progressive eyeglass lenses.
But really, most people with presbyopia – even those with no contact lens experience – can wear multifocal contact lenses successfully.
Q. Am I too old or too young to wear them?
A. Usually, presbyopia begins at around age 40. If you are presbyopic and a good candidate for contact lenses, you are a potential multifocal contact lens wearer, no matter what your age.
Q. I need reading glasses, but I don't need eyewear to see far away. Am I a candidate?
A. Yes, you can get bifocal contact lenses that have just a reading zone. Many people find this more convenient and attractive than wearing reading glasses.
Q. How do I find an eye care practitioner who fits them? Should I choose an optometrist or an ophthalmologist?
A. Call your regular eye care practitioner and ask if he or she fits multifocal contact lenses. If not, use our GP Eye Care Professional Locator. This useful resource also lists each practitioner's specialty areas, including bifocal and multifocal GPs.
Even when using this locator, confirm before making an appointment that the eye care practitioner fits GP bifocals. Fitting these lenses requires special knowledge and experience, so not every practitioner does it.
Q. Is it difficult to get used to multifocal contact lenses?
A. No. If you have adapted to bifocal, trifocal, or progressive eyeglass lenses, you will already understand the basics of using translating bifocal contact lenses, in which the distance zone is straight ahead and above center, while the reading zone is lower. With simultaneous designs, your eyes will learn to focus near or far as needed.
Whatever your particular lens design, your eye care practitioner will make sure you understand how to use it. Because all types of multifocal GP lenses, when fitted properly, move little on the eye when you blink, clinical research shows they are initially more comfortable than regular GP lenses.
Q. Do they provide vision that's as good as my bifocal eyeglasses?
A. Yes. Though there may be a slight compromise with some designs as compared with glasses, GP bifocal contacts provide especially crisp vision, as compared with soft contact lenses. The rigid material of GP lenses tends to hold a more definite shape on the wearer's eye, even after a blink.
Q. Are multifocal contact lenses expensive?
A. The cost of contact lenses varies from one lens design to another, but in general they are less expensive than eyeglasses with progressive lenses. GP multifocal contact lenses, especially, are a good value because they last longer than most soft multifocal contacts.
Q. How often will I need to replace them?
A. That depends on whether you choose soft or GP multifocals.
In general, soft contact lenses become cloudy with protein deposits over time and are easy to tear; those disadvantages are somewhat remedied by disposable or planned replacement soft multifocals.
GP contact lenses are made of a more durable plastic that stays clear over time. With GP multifocals, you may need new ones only when your presbyopia progresses so that you need a stronger near vision prescription. Read a comparison of soft contacts vs. GP contact lenses.
Q. Do they require any special care?
A. Multifocal contact lenses require no more care than regular contact lenses, and they are just as easy to apply and remove from the eye. Most wearers go all day without needing to think about their contact lenses.
Wearers of bifocal or progressive eyeglasses, however, constantly feel the weight of their glasses on their nose, must remove them for periodic cleaning, and have to put up with fogging on cold days. Reading glasses, too, are often removed and replaced several times a day, and it's easy to misplace or scratch them.
Q. What if I have astigmatism?
A. Not to worry. Multifocal contact lenses come in many designs and can be prescribed for people with astigmatism. The best choice is usually GP lenses, because they hold their shape to correct astigmatism better.