6 Steps to Maximize Success with Pseudophakic Monovision
Surgeons explain the advantages of pseudophakic monovision. Providing the best results for patients.
BY DIANE DONOFRIO ANGELUCCI
Despite the popularity of multifocal IOLs, pseudophakic monovision is still a strong contender in reducing dependence on eyeglasses. Four surgeons explain why, as well as share tips for optimal patient identification.
William F. Maloney, M.D., Maloney Eye Center, Vista, Calif., uses pseudophakic monovision much more frequently than multifocal IOLs. "Pseudophakic monovision is not for everybody, but if you look at it scientifically, it is more in keeping with the neurophysiology of the visual cortex than is the multifocal modality," he says. "Once you take a careful look at it and move beyond the marketing mantras, it becomes quite clear that not only is this a strong contender with the presbyopic IOLs, but in many cases — in my experience in the majority of cases — it's the best solution for most patients."
He explains that some patients with multifocal lenses have had difficulty with neuroadaptation, but this does not occur with authentic pseudophakic monovision because ophthalmologists measure each patient's anisometropic tolerance before surgery.
James P. Gills, M.D., founder and director of St. Luke's Cataract & Laser Institute, Tarpon Springs, Fla., uses a modified type of monovision with the crystalens (Bausch & Lomb, Rochester, N.Y.) accommodating IOL and conventional IOLs in approximately 50% of cataract patients. "In some patients we will use a crystalens in the nondominant eye for intermediate and near and in the other eye use a Tecnis [Advanced Medical Optics, Santa Ana, Calif.] single-focus lens, but we also use crystalens bilaterally, depending on what the patient's needs are," he says.
Making Monovision Work
To maximize your success with pseudophakic monovision, take these six preoperative steps:
1. Understand the Benefits. Surgeons who use pseudophakic monovision like the ability to tailor a patient's vision based on his or her lifestyle and needs, but they also cite a number of other benefits.
Patients often are drawn by the financial savings of pseudophakic monovision with conventional IOLs compared with multifocal IOLs. "When we're counseling patients preoperatively and they want to reduce their dependence on glasses, a lot of it comes down to financial considerations," says Chad Betts, M.D., R.P.H., McDonald Eye Associates, Fayetteville, Ark., who uses monofocal IOLs for monovision and a mini-monovision approach with the crystalens for patients who would like to depend less on glasses.
Furthermore, many surgeons like using monofocal IOLs because of the better results they obtain with them. In addition, "when compared to pseudophakic monovision, I feel uncomfortable with the leap of faith that is required with multifocals," Dr. Maloney says. "There's no way I can tell whether a patient is going to neuroadapt to this multifocal image or not, whereas with pseudophakic monovision I can predict with a high degree of accuracy his adaptation and tailor an approach that remains well below his threshold of acceptance."
Some surgeons prefer pseudophakic monovision because it can be reversed temporarily with contact lenses or glasses if patients are taking long driving trips or if they have difficulty adapting. "That's an advantage that I think is really appealing to a lot of surgeons as opposed to multifocals, because if you're having symptoms of waxy vision or some glare, that's not correctable very easily with glasses or a contact lens," Dr. Betts says.
Figure: Top graphic shows a defocus curve example of how a 20/40 letter E appears through a 3-mm pupil with the "distance" plano eye; the bottom graphic represents the "near" eye set at -1.50 D. This shows the quality of near vision obtained with a range of near outcomes, mostly arranged around the -1.50 D goal and the importance of hitting the "distance" target eye at plano to - 0.25 D, allowing for better adaptation to monovision.
However, some patients may need a permanent change. Dr. Gills says approximately 10% to 20% of people cannot adapt to monovision and some may require a lens exchange or refractive surgery.
2. Gauge Patients' Interest. Dr. Maloney offers pseudophakic presbyopia correction to all of his cataract patients, explaining that they may or may not be candidates for one approach or another. "In my experience 70% of our cataract patients — and it's varying a little bit with the economy — elect to have presbyopia correction with their cataract surgery," Dr. Maloney says. "That's very high." He also performs clear lens extractions in appropriate cases.
Dr. Betts' office offers patients a questionnaire with a focus zone chart developed by Dr. Maloney. Patients are asked which zone — ranging from newsprint to movies — is most important to them. "This helps you to better tailor your selection based on a patient's visual needs," Dr. Betts says. The questionnaire also asks whether it is important to them to reduce their dependence on glasses. Based on both answers, he explains their options.
3. Understand What Patients Need. Counseling the patient and determining his or her needs is very important with pseudophakic monovision and premium lenses because everyone has different needs, Dr. Betts says. For example, a patient who works on computers 10 hours a day will have different needs than someone who spends a lot of time reading books. If a patient is most concerned about computer vision and golf, Dr. Betts explains that he can select a monovision approach that will reduce the need for glasses for those tasks but stresses the tradeoff — that glasses will be needed for close reading. "The pseudophakic monovision really allows you to tailor your approach in that way," Dr. Betts says.
Dr. Betts also asks about the patient's occupation. "A couple of the drawbacks with pseudophakic monovision is you may have some visual compromise in low lighting conditions, say night driving, or there may be some decrease in depth perception," he says, so he does not offer it to pilots, truck drivers, commercial vehicle drivers and other people who need uncompromised, best-quality distance vision and good depth perception.
"I have patients who are golfers. They want to see the golf ball no matter what," says Ming Chen, M.D., F.A.C.S., clinical assistant professor of ophthalmology, University of Hawaii School of Medicine, Honolulu. He says these types of patients generally are not good candidates for pseudophakic monovision, as well as surgeons, engineers, accountants and other professionals who require perfect binocular vision for distance and near.
Dr. Maloney says occasionally a patient's personality may not be suited for pseudophakic monovision. "Pseudophakic monovision depends on neural suppression of one image or the other," he says. "The brain will do this automatically, and this neuroadaption will typically run on autopilot with authentic pseudophakic monovision unless the patient's personality wants to sabotage that process by willfully seeking out the suppressed image so as to have something to complain about. That's a very rare patient, but it's critical that you identify them beforehand."
Ophthalmologists also need to spend some time explaining monovision, which can be difficult for patients to understand. "A lot of times we'll tell them your eyes are like two cameras or two video recording devices," Dr. Betts says. "Each eye takes a picture, but then that goes back to our brain into our visual cortex. Then our brain puts the two images together by fusing them into one single image. This is referred to as binocular fusion." Or he uses the analogy of stereo surround sound. "If you have audio transmitted in the right and left channels, each ear is hearing a left and a right channel, but we don't perceive it as a separate sound," he says. "It just comes through like a single audio stream."
Dr. Maloney believes that most standard monovision explanations — one eye for distance and one eye for near — can be off putting. "I explain that one eye will emphasize mid-range and far and the other eye will emphasize the same mid-range and closer — and between the two they will blend together to give you the uncorrected range of vision tailored to your particular lifestyle and to the type of near focus you have selected," he says.
|Don't ever tell patients 100% that they're going to be out of glasses," Dr. Betts says. "Make sure they know the limitations of the options that they choose.|
4. Manage Expectations. Ophthalmologists need to explain that no lens or surgery is perfect, Dr. Chen says.
"Don't ever tell patients 100% that they're going to be out of glasses," Dr. Betts says. "Make sure they know the limitations of the options that they choose." Patients need to know that they may need reading glasses or driving glasses at some point. If a patient is unwilling to accept that he or she may need glasses for a certain range of vision, that patient probably is not a good candidate for any of the options, he says.
"We describe our technique of using crystalens, targeted for slight myopia, in the nondominant eye as supercharged monovision," Dr. Gills says, explaining to patients that monovision usually will allow them to get through much of their day without glasses, but they may need them to read a book or for more extended reading.
5. Assess Patients Meticulously. "Pseudophakic monovision succeeds or fails in the preoperative assessment, assuming an uneventful intraoperative course," Dr. Maloney says. Therefore, he performs his own preoperative biometry because, if testing is not accurate, it will undo the primary goal of the procedure. "There is a lot more surgeon involvement preoperatively, but that is an investment that makes a key difference in the quality of the outcome postoperatively," Dr. Maloney says.
Although Dr. Gills prefers to use a contact lens trial as part of the preoperative assessment, Dr. Maloney believes they can be counterproductive and produce misleading results if patients have not worn contacts before. "It doesn't give you any clinical information that can't be determined quantitatively using other tests," Dr. Maloney says. "When you're doing a 20-D lens implant versus a contact lens, the differences in the images that you're going to get optically are quite a bit different," Dr. Betts says. He may use it, however, if the patient is very hesitant.
Dr. Chen uses a contact lens trial if he believes the patient is very sensitive or is not sure the patient can adjust to monovision.
6. Boost the Odds of Success. Proper patient selection and achieving the patient's desired reading and distance goals are essential, Dr. Betts says, and he recommends staying within a -1.25- to -1.50-D range between the eyes. "If you stay within that smaller range, -1.25 D to -1.50 D, that really increases the odds of success," he says (Figure).
"When you target for more than -2.0 D, patients don't usually do well," Dr. Gills says. "I think probably the best is to target -0.25 D in the distance eye and -1.75 D or -2.0 D in the near eye, keeping the difference less than 2.0 D." Dr. Maloney agrees, adding that, "More than 2.0 D of myopic anisometropia is not necessary because there is an additional 1.0 D of effect from pseudoaccommodation."
Dr. Chen explains that mini-monovision is generally well tolerated. For the best postsurgical outcomes, he also says that it is important to treat patients before surgery if they have dry eye or keratitis.
It is also important to control astigmatism with the use of astigmatic keratotomy, limbal relaxation incisions, or toric IOLs when using pseudophakic monovision, Dr. Betts says. "If they have more than 0.75 D of cylinder or astigmatism in either eye, then you need to be able to correct that at the time of surgery if they want to reduce their dependence on glasses."
Promote a Flexible Vision
"Surgeons should be aware that the alternatives are not limited to those that are marketed by industry, that one of the best alternatives for many patients — not all — is pseudophakic monovision," Dr. Maloney says. OM
Editor's Note: None of the physicians quoted have a financial interest in products mentioned in this article.