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Expert shares controversial thoughts on presbyopia correction
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The surgical correction of presbyopia has been a special interest of mine for 3 decades. In the early 1980s, I was appointed chief medical officer for 3M Vision Care and worked with a brilliant group of scientists for more than a decade on the application of diffractive optics to contact lenses and IOLs to generate high-performance presbyopia-correcting lenses. The end result, with significant additional innovation by Alcon, was the ReSTOR family of multifocal IOLs, which is currently the global market leader.
I also engaged in research on intracorneal lenses in 1982 and accommodating IOLs in the early 1990s and have worked with thermal keratoplasty and several excimer and femtosecond laser companies on corneal reshaping. So, I definitely have a few thoughts on this area of innovation and suspect that a few of my comments will generate some controversy.
I remain engaged as a clinician and surgeon, treating presbyopia surgically in appropriate patients. Presbyopia is the most common refractive error in the U.S., with approximately 110 million presbyopes as compared to perhaps 65 million myopes or hyperopes. So, let’s get started with my first controversial thought.
Even though presbyopia is common, the patient presenting to an eye surgeon for the correction of presbyopia alone is rare. The biggest patient pool, whether it be for sophisticated eyeglasses, contact lenses or refractive surgery, is the patient with ametropia and presbyopia, not the emmetropic presbyope. Most emmetropic presbyopes simply go to the drug store or online and buy a pair of reading glasses. Very few enlist the services of any eye doctor in the effort. The patient seriously considering presbyopia surgery in almost all cases has the joint handicap of presbyopia and myopia or hyperopia, often in combination with astigmatism. In the case of an IOL implant candidate, he also in most cases has cataract, and perhaps glaucoma as well, that requires treatment. While the emmetropic presbyope rarely seeks an eye doctor’s help, one piece of good news is that most emmetropic presbyopes do not remain emmetropic as they age.
The typical 45-year-old early presbyope with a manifest refraction of plano will develop 1 D of hyperopia and some astigmatism as well by the age of 60 years, blurring vision at all distances and taking him off the Internet and into an eye doctor’s office. This means that while the mean age for the surgical correction of myopia is now approximately 35 years, the typical patient seeking treatment for presbyopia is usually 55 years or older. And of course, the 35-year-old myope who undergoes corneal refractive surgery is on his way to being an emmetropic presbyope at around 45 years, which is usually solved with a pair of readers. But at age 55 years, when he is now hyperopic and presbyopic with a little astigmatism mixed in, he is much more interested in surgical correction. Thus, the prudent practice is likely best served capturing younger patients and advising them that they will in the future want and need presbyopia correction as they age and letting them know that the practice provides these services. My thoughtful friend Dan Durrie, MD, calls this “catch and capture” as compared with the “catch and release” approach many of us thought ideal a decade ago.
Second controversial thought: I am becoming convinced that accommodating IOLs driven by capsular bag contraction forces may never achieve high commercial success. The problem is that while the accommodative reflex continues in good force after IOL implantation, the capsular bag loses the majority of its elasticity as it heals, becomes fibrotic and contracting. The enemy here is the fibrous metaplasia that not only residual lens epithelial cells lining the capsule undergo, but also the multiple other cells, including pigment epithelial cells and inflammatory cells or macrophages, that can take their place, even if we could learn to perfectly clean the capsular bag. To cause an accommodating IOL to change power through any mechanism requires that a reproducible and fairly powerful force be delivered across a reasonable distance to interact with the lens implant.
My current opinion: The wound healing biology of the capsular bag following surgery may be an insurmountable barrier to achieve good accommodative amplitudes with classic in-the-bag IOL implantation. So, we will need to move the IOL, or at least the haptic, out of the capsular bag and try to harness the force generated by the ciliary muscles or vitreous piston before it is dampened by the capsular bag. Or perhaps the answer is an electronic IOL triggered by something in the accommodative reflex such as pupillary miosis, ciliary muscle contraction or maybe even electrical activity in the nerves. As another alternative, several optical principles can be applied to increase depth of focus, including spherical aberration, small-diameter aperture optics and others alone or in combination to create a non-accommodating, non-multifocal presbyopia-correcting IOL.
My third controversial thought or hope is that the outcomes with one or more of the presbyopia-correcting small-diameter intracorneal inlays will be good enough to achieve U.S. Food and Drug Administration approval. Such an implant, placed in one eye only utilizing a modified monovision approach, will offer a much-needed surgical alternative to standard monovision or refractive lens exchange with an accommodating or multifocal IOL for those of the 78 million American baby boomers looking for reduced dependence on glasses in their presbyopic years. Approval of this technology class would reinvigorate the corneal refractive practice and industry in the U.S., which is now completing a lost decade of opportunity growth.
Finally, one last controversial thought about presbyopia-correcting IOLs. My opinion, while there is always room and need for improvement, is that the current generation of FDA-approved devices is more than adequate to generate an extremely high level of patient satisfaction so long as the patient’s eye is put into focus. The number of unhappy multifocal IOL patients who are plano sphere in both eyes with a well-centered IOL, healthy ocular surface, clear or open capsule, and normal optic nerve and macula is extremely low to nonexistent.
The main issue causing the low penetration of multifocal and accommodating IOLs in the world is surgeons’ inability to hit a refractive outcome within 0.25 D of target in all our patients. This is partly a surgeon responsibility, as there are technologies and techniques available along with refractive enhancements that can nearly always generate a good refractive outcome if the patient and surgeon are willing to do the work. But I also believe industry needs to invest more heavily in developing new techniques and technologies that will allow the lens-based refractive surgeon to achieve LASIK-like refractive outcomes for their cataract patients with an enhancement rate of less than 5%.
The next decade promises to be an exciting one for the patient desiring and the ophthalmologist offering options for the surgical correction of presbyopia. As always, it will be a choppy ride with many surprises, but for the surgeon who commits to the art and science, I predict it will be a very rewarding one as well.