|
and Jeffrey S. Eisenberg Managing Editor. |
The 52-year-old English professor who visited optometrist Rob Davis suburban Chicago practice needed a lot from her contact lenses. She taught literature at the local community college and needed crisp near vision for the amount of reading she did. She also worked at a computer frequently, so she wanted good intermediate correction. And, she still needed adequate distance vision for driving.
How would you fit this patient? Some of you would be tempted to reach for monovision first, while others believe bifocal or multifocal contact lenses are the appropriate option. Your colleagues offer their opinions of each option and discuss when each is indicated.
Why Monovision?
Dr. Davis, who is past chair of the AOAs Cornea and Contact Lens Section, applied the concept of monovision to caring for this English professor even though he fit her in multifocal lenses. We use the term monovision philosophically as the idea that one eye is a little better for distance, one a little better for near, he says.
The Frequency 55 Multifocal (CooperVision) offers a distance-centered lens for the dominant eye and a near-centered lens for the non-dominant eye.
In line with this philosophy, he fit her with a disposable spherical multifocal lens in her non-dominant eye, which gave her the crisp near vision that was critical to her job. Meanwhile, he fit a C-Vue low add monthly disposable bifocal (Unilens) in her dominant eye to allow good distance and intermediate vision.
Others may prefer a traditional monovision approach for their patients given that monovision allows uninterrupted visual acuity in each eye and requires less chair time than bifocal and multifocal fits. The reason I like monovision is because you can do so many things with it, says St. Louis optometrist Carmen Castellano. For example, monovision may be especially helpful for fitting:
Hyperopic patients. Some hyperopes require higher add power than bifocals or multifocals can provide. For these patients, monovision might better accommodate their needs.
Astigmatic patients. Although soft toric bifocal/multifocal designs are available for patients with high amounts of internal astigmatism, they are complex and expensive, says optometrist Douglas Benoit of Concord, N.H.
Younger presbyopes. These patients often fare better with monovision than with bifocal or multifocal contact lenses. This is mostly because the majority of bifocal/multifocal lenses start at adds of +1.00, and early presbyopes may get too much power at near, thus decreasing their vision or causing eyestrain, Dr. Benoit says.
Patients who are not good multifocal candidates. For example, patients with large pupil diameters or who have lenses that show inferior decentration are poor candidates for aspheric multifocals. Also, patients with a low lower lid and poor translation are poor candidates for segmented translating multifocals, says St. Louis optometrist Edward S. Bennett, executive director of the Rigid Gas Permeable Lens Institute.
Lens optic zone topograph of the Focus Progressive lens. The lens is a center near design with an intermediate range as well.
Other monovision candidates: Patients who are interested in extended or continuous wear, or patients for whom bifocals are too expensive.
Visual Compromise
Sounds good, but theres still one major drawback to monovision: You dont have the use of binocular vision as you have when both eyes are corrected equally, says Mark Andre, who runs the contact lens services at the Oregon Health and Sciences University. Also, monovision often results in a loss in near stereopsis, which can affect depth perception.
Even if monovision appears to be a good option for achieving the visual outcome for the patient, I am careful to let them know that it is not my number one choice and that distance contact lenses with reading glasses are a safer option (for driving, etc.), says Jeffrey C. Krohn, O.D., of Fresno, Calif.
Which Would You Choose?
Which is your first choice when fitting presbyopic patients in contact lenses? We asked that question in our Live Poll at Review of Optometry Online (www.revoptom.com). Of 595 responses we received as of press time, their choices were:
Multifocal contact lenses, 42%.
Monovision, 40%.
Modified monovision, 16%.
Other, 3%.
I will tell patients that, although no contact lens correction will be assured of providing the consistent quality of vision that spectacles provide, bifocal contact lenses will very likely provide, at minimum, acceptable vision for all or almost all of the tasks that you perform on a daily basis, Dr. Bennett adds.
The Choice
When deciding between monovision or bifocal contact lenses for your presbyopic patient, consider:
The Rx. In lower adds, monovision works well in many cases. But as the add increases, monovision patients can experience blur at all distances, loss of depth perception or frank double vision, Dr. Benoit says. When the add gets higher, a bifocal/multifocal is needed.
The patients occupation. Engineers and patients with high visual demands often do better with a bifocal/multifocal design, while other patients such as office workers and computer users can do very well with monovision, Dr. Benoit says.
The patients hobbies. Golfers and needlepoint buffs usually do better with bifocal/multifocal designs, while people who garden can do well with monovision, Dr. Benoit says.
The results. Consider refitting patients who are dissatisfied with monovision in bifocal contact lenses. Also keep in mind that many emerging presbyopes have worn soft lenses for years. So to them, making the transition to a soft multifocal is a piece of cake, Mr. Andre says.
Also, dont prejudge whether a patient will adjust to a gas permeable lens. A GP bifocal is a viable alternative for a patient who wants to be free of spectacles.
Soft vs. GP: Another Choice to Make
An Individual Fit
Whether you fit presbyopic contact lens patients with monovision or multifocal contact lenses, theres also the question of whether to fit them in soft or gas permeable (GP) lenses.
Soft bifocals and multifocals are an option for patients, especially current soft lens wearers who are not motivated to switch to GPs. These lenses are less expensive, and you can trial fit the patient and fine-tune the fit. GP lenses can provide crisp, clear vision, but O.D.s often dont mention this option to patients due to concern about the adaptation period.
These guidelines can help you decide between a soft and GP lens:
The patients Rx. Patients with higher corneal cylinder do better with a GP lens as do patients with a lower distance Rx relative to the add (for example, <1.00D distance Rx with a +2.25 add), says optometrist Douglas Benoit.
Generally, patients with more than -0.75D of astigmatism will fare better in gas permeable lenses. Patients with lower corneal astigmatism and/or larger distance Rxes can do well with soft contact lenses, Dr. Benoit says.
The patients visual needs. People with high visual demands in their daily activities do better with GPs in many cases, Dr. Benoit says.
Patients with critical visual requirements may be less able to tolerate soft lens bifocals/multifocals, adds optometrist Carmen Castellano.
The patients ocular health status. Patients with dry eyes often do better with GP lenses, as do patients with high oxygen demands, Dr. Benoit says.
The patients wearing preferences. Optometrist Jeffrey C. Krohn recommends soft lenses for part-time or social wear or if the patient already wears soft lenses, and gas permeable lenses for current GP wearers. J.P.S., J.S.E.
If you choose bifocal or multifocal lenses, you must tailor the combination of lenses and powers to patients individual needs. In other words, you may have two -4.00D myopes with +2.00D adds, and their solutions might be miles apart, Dr. Davis says.
So, you should stock at least three to four soft lens designs and three to four rigid lens designs. Your contact lens arsenal should include soft annular, aspheric and concentric designs, and rigid aspheric and translating designs. Some advantages and disadvantages of each:
Simultaneous vision bifocals. These lenses offer the comfort of a single-vision lens, and the angle of gaze is not important to achieve good distance or near acuity. However, some patients complain of less contrast sensitivity and poor vision quality.1
Within this category, aspheric designs offer intermediate vision, but some patients complain of visual aberration.
For those who want to use a multifocal design, yet apply a similar concept to monovision, there are already concentric designs with a circular distance center surrounded by near or vice versa. For example, the Frequency 55 Multifocal (CooperVision) offers a distance-centered lens for the dominant eye and a near-centered lens for the non-dominant eye (or you can fit two distance- or two near-centered lenses depending on the patients needs.)
Alternating designs (also called translating). These offer good distance and near vision, and newer designs offer an intermediate component for computer users.
You might even consider fitting the patient with a low-add lens on one eye and a high-add lens on the other. Other combinations: two low adds to preserve distance vision (and reading glasses worn over the contacts as needed), or an annular design in one eye and an alternating lens in the other.
Still, its a good idea to make sure the patient leaves your office with good distance vision. If youre compromising distance vision too much, theyre probably more likely than not to discontinue the lenses, Mr. Andre says.
Ongoing Relationship
Whatever approach you use, give the patient time to adapt before you make any changes. The trick is understanding what they are presently used to,
Dr. Krohn says. For example, a -2.00D myope who is taking off her single vision glasses to read will have a difficult time adjusting to the compromise inherent in any other mode of vision correction. Of course, a +1.00D hyperopic presbyope who refuses full-time correction and wears underpowered, over-the-counter reading glasses will be thrilled at the level of vision provided by hydrogel multifocal designs.
The Acuvue Bifocal is an example of a multiconcentric design with a distance center.
Still, let the patient know he or she may need to try several lenses during the adaptation phase.
Dr. Bennetts advice: Try to determine up front which patients are unlikely to succeed. Ask about the patients goals and expectations, and what is most important to them. Occasionally a patient will indicate they do not desire any compromise in their vision or that the additional expense of bifocal contact lenses is a deterrent, he says. If that is the case, prescribing spectacles may eliminate future problems.
Remember that youll be establishing a long-term relationship with each presbyopic contact lens patient, especially as their vision continues to change. Carefully explain this to each patient and become familiar with the myriad contact lens options now available for presbyopes. Who knows? These patients may not demand as much from you as they demand from their contact lenses.
1. Ghormley NR. New bifocal designs in hyper-oxygen materials. Eye Contact Lens 2003 January;29(1S):S180-1.
