September 2007

 

CATARACT/ IOL

 

Perspectives for multifocal lenses


by Leonardo Akaishi, M.D.

 

Multifocal and accommodating IOLs are among the hottest topics in cataract and refractive lens exchange surgery today. History has warned us that different IOLs in each eye of a single patient results in a failure for central nervous system adaptation to optimize the utilization of these devices. However, since each of these devices in some way represents compromise, some of our colleagues have ventured forth in mixing these devices and have found that patients have achieved better functional vision and increased spectacle independence. In a recent edition of my column, Richard Lindstrom, MD, who has been an innovator and leading advocate of this in the United States, explained his rational for mixing IOLs. In this month’s column, Dr. Leonardo Akaishi, one of the leading cataract surgeons in all of Latin America, will describe a study that he has performed of his own clinical use of mixing and matching IOLs for enhanced patient function. This is the first time we have been confronted with data. Although the numbers in some cases are small, they are certainly very illuminating. We also have an opportunity to see measures of visual function other than just visual acuity data, which is very important to all of us. I think this month’s article will help all of us who continue to be involved in our own learning curve regarding the use of these devices and for which we will continue to gain information and experience that will be of benefit to our patients.

I. Howard Fine, MD, Column Editor

 

In South America, ophthalmology is undergoing a transformation with the introduction of new lenses for both presbyopia correction and cataract surgery. Providing a wide range of alternatives, both for patients and for doctors, the ability of a patient to choose and pay for a premium IOL enpowers doctors to highlight their individually distinctive practice styles in order to attract patients as clients. Until recently, we basically had only one IOL alternative. Therefore, there was never a need to explore each patient’s distinct visual needs. Cataract surgeons performed a large number of surgeries in a short period of time. As a result, cataract surgery progressively lost its value as patients were not achieving BCVA, despite having undergone this procedure. Today, however, there are many IOL alternatives and selecting an IOL with state-of-the-art surgery have become paramount for achieving successful visual outcomes. Although there is no IOL that can meet all patients’ needs, selecting the right lens and building a good relationship between doctors and patients before surgery are now crucial issues for achieving success and meeting patient expectations. Unfortunately—or maybe fortunately—cataract surgery has become essentially similar to refractive surgery, imposing a patient-directed elevated standard for visual outcomes. Thus when surgical outcomes are not as expected—many times due to an overestimated expectation—dissatisfaction and subsequent legal suits may follow. I can say for sure that presbyopia-correcting surgery will become, in the short-term, the greatest source of legal suits worldwide. The indiscriminate dissemination of clear lens extraction for correcting presbyopia is of concern as we know little about the visual quality of multifocal lenses in presbyopic patients. There is a consensus that hyperopic patients with > 1.5 D will be happy with the exchange of a clear crystalline lens by a multifocal IOL. However, in my clinical experience, this is not always true. Some patients present with a significantly worsened quality of vision following multifocal IOL implantation when compared to patients whose BCSVA was 20/20 prior to surgery. It becomes necessary to evaluate other quality of vision indicators, such as contrast sensitivity and higher order aberrations (HOA), as well as to know a patient’s real expectations of surgery. According to Pedro Paulo Fabri, M.D., Cascavel, Brazil, the preoperative modulation transfer function (MTF) measurement is another indicator of optical quality used to ascertain the need for surgery. The optical quality of a normal crystalline lens is better than the optical quality of monofocal IOLs, and these, in turn, are better than the quality of multifocal IOLs. Thus, when we study internal aberrations, an eye with high order MTF—even with ametropia correction—can experience worsened optical quality after multifocal IOL implantation, thereby contributing to the unmet visual outcomes of a dissatisfied patient. When we perform a presbyopia-correcting surgery, an emmetropic patient must be previously informed that his/her distance vision will be worse than before in terms of quality, i.e. with halos and glare. Currently, we must spend more time with a patient during the preoperative consultation, in order to select the most adequate lens and to emphasize realistic visual outcomes. This time spent preoperatively is a crucial invest-ment for contributing to patient satisfaction postoperatively. It becomes imperative to bring past methods back—where doctors talk more with their patients, conducting a thorough evaluation, and understanding their habits and lifestyles. In order to achieve the full performance from a multifocal IOL, additional procedures may be required, whether for centering the IOL or for correcting residual ametropia. According to data recently presented by Samuel Masket, M.D., clinical professor of ophthalmology, University of Southern California at Los Angeles, approximately 13% of his patients required additional follow-up surgery. We know little about the relationship between pupil size, accommodative myosis, neurosensorial adaptation, quality of vision, and the multifocal IOL. Why do Americans and Canadians show higher levels of satisfaction with the ReZoom (Advanced Medical Optics, AMO, Santa Ana, Calif.) lens than Latin patients? Could this be because most North-Americans are taller, thereby making their reading distance longer? Or, could it be because Caucasians tend to have wider pupils, by nature? We know that pupil size is reduced as the individual ages. What would happen to patients with pupil size-dependent lenses, in the long term? Will neurosensorial adaptation really offset this loss? Thus, some misconceptions may be proven false while other questions are being raised. Multifocal lens implantation in patients with a previous history of refractive surgery (PRK, LASIK RK) is resulting in very good outcomes. In patients undergoing LASIK, myopic PRK, or post RK, we prefer to implant the Tecnis Multifocal IOL (AMO) due to the negative corneal aberration. In those patients undergoing LASIK or hyperopic PRK, we recommend the ReSTOR (Alcon, Fort Worth, Texas) lens in order to prevent negative aberration. In 55 post refractive surgery eyes, we found a mean uncorrected visual acuity of 20/35, with 8 eyes (14.5%) being submitted to a new excimer laser procedure for correcting residual diopters. The satisfaction rate was 84% and, so far, there were no multifocal IOL extrusion cases.

In patients with a multifocal IOL in one eye and a monofocal lens in the fellow eye must adjust to this combination. If the patient is left with mild myopia in the eye with the monofocal IOL, his/ her intermediate vision should be improved. Those patients must be informed that, in some situations, they may require glasses. Astigmatism is not an absolute contraindication for multifocal IOLs, provided the cornea allows for astigmatism correction and the patient is willing to undergo a second procedure. Implanting two lenses with different designs surely improves the absolute outcome. After an extensive preoperative assessment, we select the first lens. Then, 7-15 days later, we assess the patient’s satisfaction level. If we select, for example, a Tecnis MF IOL for the first eye, and, 15 days later, the patient thinks his/her distance vision is not satisfactory, we implant a Restor lens in the fellow eye. We know that the Restor IOL provides the best distance vision due to its refractive periphery and because it is less sensitive to subtle refractive error (when compared to the Tecnis MF). In a patient with a Ѕ degree of myopia, Tecnis IOL implantation results in decreased visual acuity compared to a patient with the same myopia degree but implanted with a Restor lens, as halos are less frequent with the latter lens. If the intermediate vision is not appropriate, we can implant a ReZoom lens in the fellow eye, as we know that this lens provides better intermediate vision compared to other multifocal IOLs (please, note that the pupil should be wider than 3.5 mm). Another alternative for improving intermediate vision is to implant a Tecnis MF IOL and leave the patient with a refractive error of +0.50 D.

If we select a Restor IOL for the first eye and the near vision is too close, particularly in tall patients (with long arms), the second lens should be a Tecnis MF or REZoom.

Some patients with the Restor IOL complain about the need for bright light for reading activities as they cannot read a menu in a dimly lit restaurant. In these cases, the IOL implanted in the fellow eye should be the Tecnis Multifocal, because it is fully pupil-independent. Some patients, particularly those with long arms, with <3.0 mm pupils, and who are daytime computer users, will require glasses for certain activities, including computer use. These individuals should be advised about this prior to surgery. In 40 patients in whom we implanted the Tecnis MF IOL and a ReZoom lens in the fellow eye, a vision of J3 at 60 cm was found, corresponding to a 10 point font size in a document on the computer. Overall, multifocal lenses provide the best option to help patients achieve independence from glasses. However, along withthis, we must also remember patient satisfaction—by investing time in educating and informing patients—is a crucial aspect of achieving these optimal visual outcomes.

Contact information

Akaishi
: leonardoakaishi@hobr.com.br

ABOUT THE AUTHOR

Leonardo Akaishi, M.D. is director of Hospital Ophthalmology of Brasilia, Brazil. Contact him at leonardoakaishi@hobr.com.br.


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