Should You Fit Monovision or Multifocals?
BY LISA BADOWSKI, OD, MS, FAAO
The issue of whether to refit monovision patients into multifocal lenses can stir up much debate among contact lens practitioners. Drawing from experience, I'll explain when you should refit these patients and when you shouldn't.
The Two Extremes
From my clinical experiences, I've concluded that there are three types of monovision patients. The first are the "monovision successes." These patients truly do well with monovision. They have little tendency toward ocular dominance and aren't overly sensitive to refractive blur or imbalance. Such patients will gain little from bifocal/multifocal designs and are poorly motivated to try them.
At the opposite extreme are the "monovision intolerants." These patients absolutely cannot adapt to monovision. They may have tried it in the past or just discussing it makes them squirm in your chair. Their minds are made up and there's no way it will ever work for them. Such patients make excellent candidates for bifocal/multifocal lenses.
The Monovision Survivors
The third type consists of patients that I call "monovision survivors." They currently wear monovision, and at first inquiry will tell you that they're fine with it. But if you question them more extensively, they may reveal that they never drive at night, or they have to wear their glasses for certain sports, or they've never been able to find the right distance for viewing a computer screen, etc. They use monovision because they don't want to wear spectacles. They've either heard that "bifocal contact lenses don't work" or, worse yet, they don't even know that bifocal/multifocal lenses exist. These patients are almost afraid to admit that monovision isn't completely meeting their needs because you might take their lenses away.
It is good to offer bifocal/multifocal lenses to this group of patients. Many will greatly benefit from increased binocularity and/or improved intermediate vision. Many monovision patients do well initially with monovision, but as their add needs increase, they may later develop difficulty with intermediate vision and thus become "survivors." Simply substituting a multifocal design in their near eye will often be sufficient to increase their range of vision.
A recent study (Situ, 2003) tried refitting "successful" monovision patients with Acuvue Bifocal (Vistakon) contact lenses. Twelve months following the conclusion of the study, 53 percent of the participants were still wearing the bifocal contact lenses. Because "monovision intolerants" were excluded from this study, it suggests that about half of the "successful" monovision patients were actually "monovision survivors" who did benefit from the bifocal lenses.
A Tale of Two Presbyopes
The following two cases demonstrate that it's the patient who ultimately determines what presbyopic modality you should fit.
Patient 1 presented for a comprehensive examination shortly after his 40th birthday wearing Acuvue spherical lenses (–1.50D OU). His chief concern was increasing difficulty reading small print. After discussing his contact lens options, the patient noted that he'd been uncomfortable in the past when wearing only one contact lens and so he didn't want to try monovision.
We fit him diagnostically with Acuvue Bifocal lenses (–1.50D distance, +1.00D add OU). The lenses demonstrated acceptable distance and near vision in the office, so we sent the patient home to try them in the "real world." The following week he reported much improved near vision, but said the distance vision could be better. Following over-refraction, the patient chose an additional –0.25D OD to improve distance vision without compromising near vision. At his final follow-up visit, the patient reported that he preferred to simply remove his spectacles for extended near work, but the new contact lenses worked fine for social occasions and sports activities.
Patient 2 was a 43-year-old male who had a history of spherical soft lens wear (brand unknown, –1.75D OU). He reported good vision with his current lenses. When questioned about his near vision, he said that he often wore only one contact lens in either eye (at a friend's suggestion), which worked great for most of his needs, or he just removed his spectacles for extended near work. He split his time between spectacle use and contact lens wear, but he frequently sleeps in his contact lenses when he's wearing them.
After discussing all of his options, the patient felt that his current "monovision" was meeting his needs well. We recommended a high-Dk soft lens so he could continue sleeping in lenses.
Patients 1 and 2 were both early presbyopes of similar age and refractive error. Neither minded wearing spectacles part-time, but both also wanted to continue wearing soft contact lenses especially for social functions. But that's where the similarities ended. Patient 1 was highly critical and very sensitive to small changes in power even with his single-vision prescription. He found the prescription imbalance created by a monovision correction completely unacceptable. Bifocal contact lenses with a balanced distance prescription worked best for him. Patient 2 was less discriminating and had little tendency toward ocular dominance, making him an excellent monovision candidate.
These cases illustrate how two similar presbyopic patients can require very different contact lens modalities to be successful.
For references, visit www.clspectrum.com/references.asp and click on document #124.
Dr. Badowski has served as an assistant professor of clinical optometry and chief of the Contact Lens Clinic at The Ohio State University College of Optometry. She is a diplomate in the Cornea and Contact Lens Section of the American Academy of Optometry.