If one travels outside the United States to a meeting of refractive cataract surgeons, it quickly becomes clear that trifocal diffractive/refractive optic IOLs are far more popular than the bifocal diffractive/refractive optic IOLs we currently have available here.
Extended depth of focus (EDOF) IOLs and monovision with spherical and aspheric IOLs retain a strong following, but the bifocal IOLs (called multifocal in the U.S.) most commonly utilized today in America have been mostly abandoned in other countries. The trifocal IOL market leaders are the Zeiss At Lisa, Alcon PanOptix and PhysIOL FineVision trifocal IOLs discussed in the accompanying cover story, but there are many others available from smaller companies.
All of us who are frequent users of the currently available diffractive multifocal IOLs in the U.S. know that with a bifocal IOL we have to choose our preferred distances. In a single eye we can give a patient excellent distance and intermediate or distance and near, but not excellent distance, intermediate and near. This is the promise of the trifocal IOL, and clinical experience is confirming that this optical system is increasingly popular with both refractive cataract surgeons and their patients.
Most of us believe that good distance vision is critical to achieve high patient satisfaction. When we can give only two of the three distances to a patient, we all spend significant time trying to determine which second distance to favor, intermediate or near. We can use complementary IOLs in the two eyes and get binocular vision at distance with the significant advantage of binocular summation, but we are left with a form of modified monovision at intermediate and near. A trifocal IOL in both eyes that hits the refractive target near plano in both eyes allows binocular summation at all distances. I believe this is one of the most significant advantages of the trifocal IOL, as we also know that creating three overlapping images to some extent degrades quality of vision. Clinical experience suggests that binocular summation and neuroadaptation trump the negatives of overlapping images with trifocal optics for most patients.
EDOF lenses retain a meaningful role in our practices as they give better quality of distance vision, but for many patients there is some disappointment with the near acuity achieved. Much research is being done to enhance the near outcomes of EDOF IOLs, and we can anticipate success in this area. Fortunately, trifocal IOLs are also undergoing FDA investigational device exemption clinical trials in the United States, and the first one should become available in the coming years.
The ultimate goal is a refractive optic accommodating IOL with 3 D or more of accommodative amplitude or perhaps a lens that combines 1.5 D of accommodation with 1.5 D of EDOF. The day will come when we can implant an IOL that truly replaces the vision enjoyed by the pre-presbyopic emmetrope. When that day comes, lens replacement surgery will become the most common form of refractive surgery performed, and patients will seek it at younger ages. The ophthalmologist younger than 50 years will experience this technology-driven disruptive change in practice during their career, and the challenge will be meeting the demand at a reasonable cost. Bilateral same-day natural lens replacement surgery with an accommodating IOL, likely done in an office-based surgery center, will become the most common and most successful surgery done in all of medicine.
Disclosure: Lindstrom reports he is a consultant for Alcon, Bausch + Lomb, Johnson & Johnson Vision, Zeiss and ForeSight 6.