There are several ways of fitting contacts for patients who require a bifocal. Bifocal contacts, of course, are one option. Other options include a monovision contact lens fit, modified monovision, and a combination of distant vision contacts and reading glasses. I will discuss these options further, along with my impressions of the advantages and disadvantages of each.
Bifocal Contact Lenses
Bifocal contact lenses allow patients to see both distant and near at the same time. They are available in both soft and rigid gas permeable material.
The main advantage of bifocal contacts is better depth perception at both near and far. This is especially true when compared to monovision. Disadvantages include increased glare at night and a possible compromise in either the near or distant vision. The latter has been my experience with the soft simultaneous vision bifocal contacts (see below). It can be very difficult to achieve both good near and distant vision with these lenses. It seems that if we get the distant vision in good focus, the near vision suffers and vice versa. In these cases, I will sometimes try the modified monovision option (see below).
Within the category of bifocal contact lenses, there are simultaneous vision and translating (also know as alternating) bifocal contacts.
Simultaneous Vision Bifocal Contact Lenses
For simultaneous vision bifocal contact lenses, patients receive images from multiple distances at the same time. The brain must then choose which images to ignore based on the distance to the objects. The variety of lens designs available allows for near, intermediate, and distance vision correction. Simultaneous vision bifocal contact lenses are available in both soft and gas permeable materials. This category can be further broken down into aspheric, concentric, and diffractive lenses.
Aspheric Lenses
Aspheric contact lenses use a technology that creates a multifocal effect. What you need to know here is that these lenses produce an effect comparable to the progressive bifocal that is popular in spectacles. Some lenses within this category favor the distance vision, while others favor the intermediate or near vision. All these lenses, however, should yield some intermediate correction.
Picking the best lens depends on a patient’s occupational demands (among other things). I have had some with both Bausch & Lomb’s Soflens Multifocal as well as Ciba’s Focus Progressive contacts.
Concentric Lenses
Concentric contact lenses have a central distance or near zone followed by one or more “rings” of the opposite power. One of the more popular lenses in this category is the Acuvue Bifocal made by Vistakon which is owned by Johnson & Johnson). I’ve had fairly good success fitting this lens (around 60% success rate). However, concentric contact lenses do not correct for the intermediate vision, as well as the aspheric lenses, do.
Diffractive Lenses
Diffractive contact lenses diffract (“splits”) light entering the eye into different images depending on image distance. Cooper Vision’s Echelon is the primary lens of choice in this category. I personally have never fit this lens, but I have colleagues who have fairly good success.
Translating (Alternating Image) Bifocal Contact Lenses
The translating bifocal contact lens design is similar in concept to the bifocal you see in an individual’s glasses. There are specific areas for the distance and near correction. Typically the top of the lens is the distance correction, with the near being in the lower portion. To view items at near, the patient must look down, thereby placing the near correction in front of the pupil. One of the more popular lenses in this category would be the Tangent Streak made by Fused contacts. This lens is available in both bifocal and trifocal prescriptions.
The primary disadvantage of the translating bifocal contact lens is that, as with spectacles, the patient must move his/her eyes downward to use the near portion of the lens. Therefore, this design is not a good option for those individuals who need to view close objects in the straight-ahead position.
Monovision
Monovision contact lens wear is where one eye – usually the dominant eye – is corrected for distant vision and the other eye is corrected for near vision. When the patient views objects in the distance, the brain learns to suppress (at least this is the goal) the image in the eye corrected for near vision and vice versa.
Wearing a monovision contact lens correction is a good option for those patients who cannot wear a bifocal contact lens and still wish to avoid wearing spectacles. As with bifocal contacts, the brain must choose between “competing” images, which can lead to compromised near as well as distant vision. Also, since the two eyes are not receiving the same prescription for near or distant at the same time, there is a decrease in-depth perception. This potential problem also increases as the bifocal power increases.
Nevertheless, monovision enjoys probably the highest level of success in fitting patients who require a bifocal. Studies have shown that the success rate runs between 70 and 80%. This success rate is generally attributed to better overall vision (as compared to bifocal contacts, for example) and less fitting time involved. In my experience, I would agree with this assessment.
Modified Monovision
Modified monovision, also referred to as enhanced monovision, entails emphasizing distance correction for one eye – typically the dominant eye – and near correction for in the other eye. Bifocal lenses may be used in both or only one eye, depending on the situation. This works best for those patients who want or need better distance vision than what is sometimes achievable with bifocal contacts but also wants some near correction in the contacts. This allows those patients to continue avoiding spectacles.
I would estimate that about 40% of my patients who successfully wear bifocal contacts do so with the modified monovision option – at least part of the time.
Distance Vision Contacts with Reading Glasses
This method of wearing contacts involves the use of distance only contacts for both eyes with the use of reading glasses (also called “readers” or “magnifiers”) over the contacts for near vision. This allows for sharp distance and near vision. There is no reduction in-depth perception, as can happen with bifocal contact lens options.
This method of wearing contacts probably yields the highest level of success for those patients who need a bifocal. However, as you may have guessed, many do not prefer this method as glasses are still required at least part-time.
Nevertheless, I generally advise this mode of wear for those patients who spend a lot of time in front of a computer or doing anything for long periods of time at near.
Last But Not Least…
Bifocal contact lenses involve many of the same compromises in vision that spectacle bifocals have. However, being informed and having realistic expectations can only help if you do decide to try these lenses.
Most of the bifocal contact lens modalities discussed are available for patients to try in the prescribing doctor’s office before actually buying any contacts. There is no cost other than the professional fees. This is typically the case for disposable and planned replacement contacts.
For non disposable contacts, the patient typically would be required to pay upfront for both the contacts (or apply for any insurance benefit) and the professional fees. However, it has been my experience that in the latter case, if a patient is unable to successfully wear the prescribed contacts, most offices will refund what the patient paid for the contacts, but not the professional fees. What this means to the patient is that if he/she ever considered trying bifocal contacts, they can do so with minimal financial risk.
This “minimal risk” environment applies not only to bifocal contacts but to just about any contact lens out there. Of course, it is advisable to discuss your doctor’s office policies before getting your eye exam and contact lens fitting.