point TOPIC: Monovision Versus Multifocals
Newer is not Always Better
BY CARMEN F. CASTELLANO, OD, FAAO
Due to a number of advances in technology and lens designs, we currently have more contact lens options for our presbyopic patients than ever before. In recent times a number of viable multifocal contact lens designs have entered the market. Though these are welcome additions to our armamentaria, we should also remember that monovision has remained a tried-and-true method of correcting presbyopes for many years, and in many cases can be a better option than multifocals.
In the course of fitting multifocal lenses, it is often necessary to incorporate a degree of "modified monovision" to achieve success. In fact, some multifocal designs are intended to be used in this manner in the first place. Therefore, even with multifocals, we are not necessarily abandoning the concept of monovision in spite of what we may think.
The point is, as we celebrate the improvements in the industry, we should be careful not to dismiss monovision in a negative manner.
A Proven Track Record
The key to successfully treating presbyopia is to recognize that there is no perfect system. This is true of simple reading glasses, progressive addition and lined bifocal spectacle lenses, multifocal contact lenses, and monovision.
Over the years, studies have shown monovision to be successful 60-to-85 percent of the time. Until recently, multifocal contact lenses have typically not claimed this degree of success.
In addition, many patients prefer the clear, uninterrupted vision in each eye provided by a monovision correction, as opposed to the somewhat reduced visual quality experienced with multifocal lenses. In other words it's up to patients to decide whether it's better to have good binocular vision of reduced visual quality or to have clear vision in each eye, though not focused together.
The rap against monovision is that it seriously compromises "depth perception," yet we all learned early in our physiological optics training that we use a number of clues to judge "depth" and only one (stereopsis) involves the use of both eyes. In addition, it is important to realize that monovision is not occlusion, and very usable peripheral vision remains intact.
Correction for More Patients
Another advantage of monovision is that it offers more lens options for treating astigmatic patients, those who have unusual prescriptions or lens design needs, patients who have unusually large or small pupils, and those opting for continuous wear.
Also, in the case of GP translating bifocals, for which a low inferior lid position might preclude success, monovision can be an excellent alternative.
Over Spectacles Are an Option
For patients who do well with monovision for most activities but may have difficulty with night driving or prolonged, concentrated near tasks, a part-time spectacle correction over the lenses can be an easy solution. For those wearing multifocals who still find certain areas of their vision deficient, a spectacle over correction is not necessarily workable as the multifocal lens optical system is much more complicated.
Rely on What Works
As the Baby Boom Generation continues to mature and the Generation X patients enter their presbyopic years, there is a tremendous opportunity for us to grow our contact lens practices and for the industry to thrive. It is this age group that has the most disposable income and is willing to spend for products and services that make them look and feel younger. We should take full advantage of this opportunity by using all avenues available to best serve these patients. CLS
Dr. Castellano is owner of The Koetting Associates, an optometric group practice specializing in contact lenses. He currently serves as an adjunct assistant professor at the University of Missouri-St. Louis School of Optometry, the Pacific University College of Optometry, and the Department of Ophthalmology and Visual Science at the Washington University School of Medicine. He has received research funds from B&L and CIBA.
Time to Clean Out the Closet
BY PETE S. KOLLBAUM, OD, PHD, FAAO
I must admit that I do really like monovision as a presbyopic contact lens correction modality. However, I also really like a comfortable pair of jeans that I've had for the last 15 years. This makes me wonder whether monovision, although "comfortable" to me as a presbyopic correction modality, is still the best method. With this in mind, I will briefly highlight some reasons why I have always believed monovision to be the initial presbyopic correction of choice — and why these reasons may no longer be appropriate.
Five Reasons to Consider
1. Patients adapt to monovision easier than to multifocals, making monovision ideal for new presbyopic lens wearers. I have always thought that monovision was good for early presbyopes, as the prescription of one eye can be slightly altered, making an easy transition into presbyopic contact lens correction.
However, in a recent study of emerging presbyopes who were randomized to either a new multifocal lens design or to monovision, subjects rated their overall visual satisfaction significantly higher with the multifocal lenses (Kollbaum, 2008). They also rated the multifocals as providing improved distance, night, and computer vision.
2. Monovision takes less chair time. It seems reasonable to assume that fitting monovision is comparable to fitting other single vision lenses and so should take less chair time compared to fitting multifocals.
However, a recent study (Woods, 2008) found no significant difference in the number of lenses required to achieve an optimized fit with a recently developed multifocal lens versus monovision. This perception may have been true for older lens designs, but not for newer designs.
3. Monovision is less expensive compared to multifocals. This issue seems very straightforward. The cost of a six-month supply of single vision lenses is around $40, while comparable multifocal lenses are around $80.
I wonder, though, if this cost difference is truly as important to patients as we think. I know that whenever I buy anything, I try to buy "the best" latest and greatest technology. Granted I am a technology buff, but I don't think this is uncommon. I've had many patients who, after I inform them of their options, ask me what I would choose. Maybe the cost-benefit ratio of multifocals isn't as high as we think. Recommending multifocals may also have the added benefit of purveying to your patients that your practice is state-of-the-art, potentially boosting your patient load.
4. Vision with multifocals is worse than with monovision in low light situations because of ghosting. In the study mentioned previously (Kollbaum 2008), new wearer preference was significantly higher in multifocals for night driving, and multifocal wearers also experienced less ghosting. Measured low-illumination, low-contrast acuity was also significantly better in multifocals compared to monovision.
5. The loss of stereoacuity with monovision doesn't really have an impact in the real world. I have questioned the importance of near stereoacuity on typical real world activities. I've had many monovision patients able to perform near tasks that require stereoacuity, such as threading a needle, without problems.
However, improved stereoacuity has been cited as a reason why patients may prefer multifocals over monovision, even if the measured visual performance was quite similar (Richdale, 2006).
Time to Reconsider
In closing, I must admit one other thing — I gave my favorite old jeans to Goodwill. Maybe it is time we all cleaned out our closets, or at least revisited what items we have in there and when we use them. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #169.
Dr. Kollbaum is an assistant professor at the Indiana University School of Optometry, where he teaches and performs research in the areas of contact lenses and optics and is director of the Clinical Optics Research Lab. He has received research funding from CIBA, CooperVision, Alcon, and Visioneering Technologies.