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Nuances of presbyopia-correcting IOLs broaden range of treatment options
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I would like to share a few thoughts on presbyopia-correcting IOLs. This has been an area of personal interest for more than 35 years. I served as chief medical officer for 3M Vision Care when the first diffractive multifocal IOLs were developed and investigated. I also consulted for Iolab and AMO when the first refractive multifocal IOLs were developed and investigated. I was a consultant to and served on the board of directors of eyeonics when Crystalens was developed and investigated, the first and only FDA-approved accommodating IOL. I continue to consult for many of the leaders in the field as they develop the next generation of presbyopia-correcting IOLs, which includes the new category of extended depth of focus IOLs, discussed in the accompanying cover story. I have used all of these presbyopia-correcting IOLs in my personal private practice — excluding trifocal multifocal IOLs, which are not yet available in the U.S. — which includes cataract surgery.
First, patient satisfaction is extremely high with all of the presbyopia-correcting IOLs, and monovision as well, when the individual patient’s preferred refractive target is hit. We learned this in the early days at 3M. We did a large clinical trial looking at multiple variables including patient personality, and the only variable that correlated with patient satisfaction was hitting the refractive target. When the refractive target is hit, patient satisfaction and willingness to recommend a similar procedure to friends and family are in the 90% to 95% range, which is similar to that found in LASIK.
Different surgeons might select different targets depending on the IOL and patient being operated upon, which is as it should be, customizing the procedure for the individual patient. However, my experience is that the residual astigmatism should be near zero and that even 0.25 D of residual cylinder can significantly degrade image quality in a multifocal IOL. In addition, the ideal outcome for higher-order aberrations is also near zero. Spherical equivalent targets vary some by lens style and can be different in the two eyes of a single patient, especially in monovision. This is an extremely high standard for a multifocal IOL: plano sphere and no higher-order aberrations for the highest level of patient satisfaction, but the facts are the facts. That is what our patients want.
In order to even approach this standard, I find postoperative refraction and use of the excimer laser to fine-tune refractive outcomes are an absolute requirement in my presbyopia-correcting IOL practice. As all of us know from fitting spectacles and contact lenses that patients can easily detect a quality of vision difference at the 0.25 D level, and for many even 0.125 D is meaningful. In toric IOLs, axis alignment that is off more than a few degrees is clinically meaningful. Because only about 2,500 of the 10,000 American surgeons who do cataract surgery are comfortable performing PRK or LASIK, we desperately need an adjustable IOL. The first-generation product from RxSight has just achieved FDA approval, and the second-generation product holds promise to manage sphere, cylinder and higher-order aberrations based on the patient’s desired refractive outcome of each individual eye determined at postoperative testing. This will, in my opinion, be a welcome and disruptive advance. Pioneering work to adjust refractive error with femtosecond laser application to an IOL is also extraordinarily exciting to me.
Second, and perhaps more controversial, I have become convinced that the same IOL does not have to be implanted in both eyes of an individual patient. Over 40 years of implanting presbyopia-correcting IOLs, I have used every combination you can imagine. With postoperative fine-tuning of the refractive outcome using laser corneal refractive surgery, patient satisfaction is high with all of them. It is obvious in monovision that the spherical refractive target will be different in the two eyes, but my experience is that even with multifocal, EDOF and accommodating IOLs, ideal refractive targets can vary from one eye to the other. Unfortunately, the ideal refractive outcome for each eye cannot be determined until after the surgery is completed. Today, the best fine-tuning instruments I own perform laser corneal refractive surgery. I see the future being one or another form of laser pseudophakic refractive surgery with an adjustable IOL.
Third, while I remain excited about the idea of bilateral same-day sequential cataract surgery when using monofocal IOLs, I am an advocate of so-called “staged implantation” when using a presbyopia-correcting IOL. Today, I nearly always implant an EDOF IOL in the first eye (usually a Tecnis Symfony, Johnson & Johnson Vision). I then evaluate the visual outcome and symptoms at 2 weeks postoperatively. In most patients satisfaction is high, and I implant the same IOL in the second eye. In about 5% of patients, I find dissatisfaction with uncorrected near vision. I have tried targeting mild myopia in the second eye using mini monovision, and this certainly can work, but my current preference is to implant a multifocal IOL in the second eye with better near vision capability (for me usually a Tecnis ZLB00 3.25 D add multifocal). This combination of an EDOF IOL in one eye and a more near dominant multifocal IOL in the second eye has worked extremely well for me.
In the near future, I also look forward to accessing the AcuFocus IC-8, which seems well designed for the patient with significant higher-order aberrations. I see the IC-8 as a unique IOL with a specific indication. In a practice like mine with a large number of prior RK, anterior lamellar keratoplasty, LASIK, PRK and keratoconus patients, the IC-8 will be a welcome addition to my options.
I could go on for hours, and often do with my similarly interested friends at various social and meeting venues. That so-called experts in the field can debate the nuances of presbyopia-correcting IOLs for hours teaches me that we still have much to learn. The last five decades of the innovation cycle have brought us five presbyopia-correcting IOL options: monovision, multifocal, accommodating, EDOF and small diameter aperture IOLs. Next in America will be the adjustable IOL and a trifocal multifocal IOL. The ultimate goal: a 4 D or greater accommodating adjustable IOL, which by the way has a zero incidence of posterior capsular opacity requiring a posterior capsulotomy after surgery. The patients will be ever younger and the lenses being removed ever softer or softened at surgery, so that phaco-aspiration is sufficient and no ultrasound energy is required. After a 50-year run, emulsification of lenses with ultrasound will be rare. Complications will diminish, and demand will progressively increase. The rate-limiting factors for even the most advanced countries will be economics and an adequate number of trained surgeons to do the work. But that is the topic of another commentary.
Disclosure: Lindstrom reports he consults for Johnson & Johnson Vision, Alcon, Bausch + Lomb, Zeiss, AcuFocus, Foresight 6, RxSight, Precision Lens, Visionary Venture, Flying L Ventures, Unifeye Vision Partners and Elenza.