Chapter 15

J. E. “Jay” McDonald II, MD and Garth Rotramel, BA, SPHR

The purpose of this chapter is to provide you, the practitioner, with a hands-on method for successfully making pseudophakic aspheric advanced monovision a working piece of your presbyopic cataract repertoire.

BACKGROUND AND HISTORY OF MONOVISION

Today, the average person is using a personal digital assistant (PDA) 30 to 60 hours a week. The point of focus is no longer a book. Reading glasses and bifocals are a poor and debilitating choice. Future patients will no longer tolerate these archaic appliances. The need for the monovision platform for near and far has never been greater. Every lens replacement surgeon needs the ability to give his or her patient a spectacle-free ability to function in today’s world.

Thirty years of clinical, optical, and surgical practice have taught me that the prescription people comfortably function with is not always identical to what comes out of the phoropter. My eyes were opened to the fact that the patient’s best fit is much more powerful and important than a person’s 2 individual prescriptions. In fact, in treating presbyopia, visual function can be expanded greatly by learning and appreciating the power of bilateral integrative visual function.

Prior to the development of the intraocular lens (IOL), we used contact lenses to reduce size disparity to within 7% of the phakic eye, and the uniocular aphakic patient was visually “made whole.”

Monovision soft contact lens fitting provided the plano presbyope the appreciation of not having to raise the chin in order to type, read, order from a menu, or work on a factory line. Pilots, finish carpenters, and office workers no longer had to rely on bifocals or trifocals to visually function.

In 1998, Greenbaum reported using intraocular monovision in his postoperative cataract patients by targeting -2.50 myopia in their nondominant eye and targeting plano in their dominant eye.1 He was successful in producing happy postoperative cataract patients who could read without spectacle correction.

Currently, in our practice, by using aspheric IOLs, we precisely target a separation of only -1.25. This is almost universally successful, as the difference in intraocular images is minimal. Stereopsis is preserved in the 40- to 60-second range. More importantly, by using monofocality rather than splitting the image with multifocality, we maximally preserve, for the patient’s lifetime, the highest quality of optical and visual potential. In Figure 15-1, we can see the progression of the uniocular image from near to far.

The fact is, the patient over age 60 years rarely has a pupil greater than 3.2 mm.² This small pupil creates the continual depth of focus that, as demonstrated in Figure 15-1, produces a bilateral clarity of vision from 24 inches to infinity. This small amount of refractive separation is well accepted by every patient but the most strongly eye dominant person.³ Currently being validated is a quantitative ocular dominance testing device that will help us broaden our scope of identifying, on a spectrum, a person’s relative tolerance to what we shall call blended vision.4

Monovision provides a highly successful mechanism to deliver spectacle independence for our presbyopic patients. Doing so requires considerable additional evaluation, as well as staff and doctor skill refinements. Additional testing, new staff counseling, and the surgeon’s ability to eliminate astigmatism—both intra- and postoperatively—is demanded. Thus, entering the presbyopic surgical arena, whether using accommodative, multifocal, or advanced aspheric monovision, must be undertaken seriously. However, the reward of spectacle independence for the patient and doctor more than warrants this extra energy by the doctor and staff and expenditure by the patient.

The Centers for Medicare and Medicaid Services Ruling No. 05-01 provides a mechanism so that a patient can be responsible for payment of that portion of the physician’s charge for a presbyopia-correcting IOL exceeding the physician’s charge for a conventional IOL following cataract surgery. In 2005, after several meetings and discussions with Kevin Corcoran, a longtime respected reimbursement consultant, our practice arrived at a proper charge and fee evaluation for the process leading to spectacle independence through pseudophakic monovision. Unlike the multifocal and accommodative lenses, there is not a significant charge for the lens products involved, thus making the charge more affordable for our patients while allowing for great satisfaction. Corcoran and associates are happy to provide the forms and information surrounding this at their website (www.corcoranccg.com).

In our community, we have not only been able to afford the increased time and resources required to implement these services in our clinic, but we have been able to save our patients thousands of dollars in out-of-pocket costs related to premium lens products. The out-of-pocket expense of a costly multifocal lens is avoided. At the same time, the surgeon’s additional staff time, skill set, and increased postoperative time is covered by a justifiable out-of-pocket amount commensurate with a multifocal IOL use.

WHY MONOFOCALITY VERSUS MULTIFOCALITY?

The answer to this question requires a long and detailed process that involves my personal journey of several years working through the current knowledge of the neurocognitive processes involved in binocular vision. I owe this awareness to many colleagues directly or indirectly involved in the visual sciences as well as clinicians, most notably Randolph Blake, PhD; Martin Mainster, MD, PhD; Patricia Turner, MD; Griffith Altmann, MS, MBA, Director of Global Product Strategy for Intraocular Lens Products at Bausch & Lomb; Richard Lindstrom, MD; and Jack Holladay, MD. I believe very strongly that as a given patient ages, he or she incurs normal deterioration of his or her visual processes and often visual pathology; the contrast sensitivity deficit created by the use of multifocality may, in fact, become material in his or her visual function (Figure 15-2).

For further discussion and a more detailed description of aspheric monovision and its optical and neurocognitive superiority to current multifocal techniques of presbyopic IOL correction, I refer you to Chapters 77 and 78 written on this subject in Mastering Refractive IOLs: The Art and the Science by Dr. David F. Chang.^5,6

From a very practical standpoint, monovision, from day 1, provides the surgeon and patient the best alternative. By utilizing a pair of spectacles, monovision always affords the patient and the surgeon the best “fall-back position.” The patient’s optical neuroprocessing bases are never compromised. The patient has instant access to a full binocular complement of vision by simply utilizing a pair of spectacles. Similarly, night vision can be instantly restored to its fullest visual potential by supplementation with a pair of spectacles. Thus, when the surgeon uses aspheric monofocal presbyopic IOL correction, he or she never backs him- or herself or his or her patient into a potentially visually compromised situation.7

INTEGRATING MONOVISION OPTION INTO THE PRESBYOPIC PREMIUM CHANNEL

Delivering spectacle independence using monovision requires the same precise patient education, staff attention and awareness, and accurate biometrics and surgical skill sets as any other form of presbyopic surgery. It requires a complete complement of staff and physician skills.

Astigmatism correction is a necessary component for the success of any premium choice, and generally the patient will need to have 0.5 diopter (D) or less to be successful.8 Because correcting astigmatism is a surgical procedure not covered by insurance or Medicare, and because it may require an enhancement about 20% of the time, there is a significant cost to this enhancement process. This cost is in addition to the cost of continuous vision or blended vision. Most patients with astigmatism are aware of their condition and, in fact, we find they easily accept this component and its cost. Remember, these patients have had their spectacle prescription altered by their optometrists due to their astigmatism throughout their lifetime of eyeglass purchases.

How Is the Charge for Monovision Addressed?

If one selects advanced aspheric monovision, or, as we refer to it, blended vision or continuous vision, the patient incurs a global charge. These tests are listed in Table 15-1.

The documentation of this is available at Corcoran’s Web site (www.corcoranccg.com). The additional testing is coded as a super refraction, as well as an assessment of additional cognitive skills that enhance or detract from the success of monovision. Topography reveals whether there is any corneal impediment to blended vision success, as each eye after cataract surgery must individually deliver a noncompromised image in order for the cortical component of blended vision to work. The one thing I do not do is a contact lens trial. I have found even the process of putting in the contact lens discourages the patient, as well as the fact that at least a 3-week period of successful contact lens all-time wear is required in order for the patient to neuroadapt.

We have found adapting to IOL monovision is easier than monovision with contact lens. We have never done contact lens trials of monovision to predict IOL monovision success, just as we never used spectacle monovision trials to predict the success of contact lens monovision.

What Are the Compromises of Monovision?

Binocular IOL monovision is great but not perfect. There is some loss of best acuity in low contrast. With the use of PDAs as well as computer screens for near, the higher screen vs paper contrast provides acceptable near component with a lower-power near. There is some small loss of measurable stereopsis, but this is inconsequential when viewing a PDA or computer screen. We find those with strong preoperative stereopsis maintain a strong tendency for high-level stereopsis postoperatively and adapt easily. If a patient expresses some anxiety about adaptation, at each point of the examination, he or she is reassured that almost anyone can adapt. The results can always be reversed by, at worst, wearing a pair of glasses. I also hold in reserve, and use occasionally, the removal of the near eye correction with, almost always, a mini-radial keratotomy (usually 2 incisions, sometimes 4), as described in Chapter 16 of this book. Surgeons not comfortable with incisional surgery for myopia can always use laser vision correction as their fallback position, or simply a pair of reading glasses. The reassurance that aspheric monovision can be removed with a simple refractive procedure, when said with assurance, is the most important comfort factor for the person undergoing spectacle-independence surgery. The willingness to do so releases almost all of the patient’s anxiety. This refractive touch-up is much easier for me and less anxiety producing for the patient than having to go back and remove a multifocal lens in order to reverse a multifocal lens choice. The actual occurrence of this in our practice is less than 0.01%.

The Surgeon’s Role

By the time the patient reaches the doctor, most of the questions have been answered by the highly trained tech. The patient has made his or her choice, and I usually end up spending less than 5 minutes of my time answering questions. I explain that our eyes are like television cameras and that, in actuality, “we see with our brain.”

If the patient expresses doubt about his or her being able to adapt to blended vision, I show him or her how with one eye occluded we see our nose, but with both eyes open we do not. I may also add that if we truly saw with our eyes, our world would jiggle up and down with every step we took. I reassure them that 95% of people will adapt, and if they do not, they can always wear a pair of glasses or have their monovision surgically reversed. We are talking about, at most, a -1.25 surgical procedure.

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