In the years since IOLs were approved for widespread use in patients some 40 years ago, IOL technology has been the focus of intense R&D driven by the needs and preferences of both patients and surgeons.
Today, a variety of novel lens designs can correct for presbyopia and astigmatism in addition to myopia. Advanced-technology or premium IOLs include new shapes built from entirely new materials, and a compendium of new tactics, tools and techniques has arisen to complement the basic technology.
The following is a brief review of the current state of the art.
CURRENTLY AVAILABLE TECHNOLOGY
Meeting patient expectations
Surgeons and patients were once delighted with a postoperative outcome that included the need for glasses, contacts or even additional procedures with a laser or a scalpel. Now, of course, the expectation is a future free of presbyopia, astigmatism and corrective spectacles or contact lenses. Premium IOL types and the principles upon which they work are putting that expectation within reach.
Multiple zones of lens power producing more than one focal point can enhance near and far vision; this effect is used in multifocal contact lenses and IOLs alike. Regarding their focality, multifocal IOLs can be classified as bifocal, trifocal or extended depth of focus (EDOF).
With the optimal result being spectacle independence, multifocal IOLs may underserve the intermediate zone, and acuity there can suffer. Happily, however, newer models seek to address this weakness through various approaches.
Multifocal patient education: Keep it simple
“I keep my discussions with patients very simple,” says Vance Thompson, MD. “I think it’s important to explain to them what the lens does: it provides reading range plus clarity. The choice is, do they want to correct the clarity only or both clarity and reading range at the same time.” Dr. Thompson is director of refractive surgery at Vance Thompson Vision in Sioux Falls, S.D.
If patients want to correct both, he says, and do more activities without glasses, the trifocal comes into play. “With PanOptix, we can cover all three distances — near, intermediate and far — in a balanced way without mixing and matching two lenses,” Dr. Thompson says. “Patients are looking to me to recommend an approach, and that is where the examination becomes crucial. We need to ensure the health of the cornea and the tear film and quantify the cornea’s optical quality to be successful, and good trifocal candidates have low amounts of higher-order aberrations and, of course, a healthy macula and optic nerve.”
Dr. Thompson participated in clinical trials for PanOptix and notes that there is a neural adaptation period. “We explain to patients that there is a time period when their brain is getting used to their new trifocal optical system. In the FDA-monitored trials, patient satisfaction one month postoperatively was good but one year later was great.”
Multifocal IOLs can be classified as refractive or diffractive IOLs in terms of the optical design and physical principles. Refractive multifocal IOLs have ring- or sector-shaped optical zones with different dioptric powers on the anterior surface and are based on geometric light rays’ refraction principles.
Diffractive implants, on the other hand, have multiple diffractive zones on the posterior IOL surface causing interference of optic wavefronts. Each has its pros and cons, so a careful evaluation is necessary to find the most appropriate solution for each patient.
When multifocal IOL principles are dependent on pupil size, photic phenomena can result. Diffractive multifocal IOLs tend to display more stray light than refractive ones, and control trials have repeatedly revealed a significantly higher rate of dysphotopsias in patients with multifocal IOLs compared to monofocal IOLs. Nevertheless, overall patient satisfaction and quality of life after multifocal IOL implantation are very high.1
Here is a summary of the available multifocal lenses:
- Diffractive bifocals. Diffractive bifocal IOLs produce near and far images distinctly. The first on the market was the AcrySof Restor (Alcon), which earned FDA approval in 2005. It functions via apodization, whereby the center of the disc is used for near vision. Surrounding it are concentric rings of decreasing height that enable distance vision. The Tecnis Multifocal IOL (Johnson & Johnson Vision) has an aspheric anterior surface with diffractive rings on its posterior surface that focus both near and distance light irrespective of pupil size. A drawback with diffractive IOLs can be poor intermediate vision compared with other designs.1
- Diffractive trifocals. Wide, flat defocus curves help trifocal IOLs produce fewer visual side effects, thereby improving vision. In many areas outside of the United States, the trifocal IOL is popular for presbyopia correction, because it improves intermediate vision by providing an additional focus beyond the bifocal’s two. In the United States, Alcon’s PanOptix is the sole trifocal technology available. In a pivotal trial, more than 99% of patients implanted with the lens said they would choose it again.2
- EDOF. These lenses are designed to provide a deep field of focus without reducing distance visual acuity. They seek to achieve this by adjusting the spherical aberration of the lens to elongate incoming light waves, thereby eliminating halos and overlapping far and near images. With the improvement in intermediate vision, there can be a decrease in the quality of retinal images. Johnson & Johnson Vision’s Symfony EDOF IOL achieves its goal through its echelette design, which diminishes chromatic and negative spherical aberration. It improves intermediate vision compared to monofocal controls, and patients report fewer aberrations and enhanced contrast sensitivity.3,4 EDOF properties can also be combined with other types of IOL technologies to beneficially merge their characteristics.
Marjan Farid, MD, director of cornea, cataract and refractive surgery, Gavin Herbert Eye Institute, UC-Irvine, says her approach has evolved over the years to “personalized vision”: using the Symfony EDOF in the dominant eye and the Tecnis Multifocal +3.25 in the nondominant eye. She says that the combination provides excellent “total vision, fills in all of the gaps and maintains contrast sensitivity.”
Accommodation is the change in the refractive power of the eye when the image of a near object is brought into focus on the retina. Because it has the ability to change its shape in response to eye muscle movements, an accommodative lens is one that can change its power while in use.
Premium monofocal disruption
The Light Adjustable Lens (RxSight) has been designated as a premium IOL by the Center for Medicare and Medicare Services with a price about 1.5 times that of a standard toric implant. John Berdahl, MD, who has been involved in clinical trials for this technology for more than 8 years, says it has received excellent patient acceptance since its rollout.
Because patients are brought back for adjustments — three times after three weeks — considerations must be given for how this technology impacts clinic flow.
In a clinical trial, 92% of patients got within 0.50 D of the visual goal with just two light adjustments, notes Dr. Thompson, who also was involved in securing the IOL’s FDA approval. With three adjustments now permitted, even more of his patients are on target.
Currently, the Crystalens IOL (Bausch + Lomb) is the only FDA-approved accommodative IOL. It simulates the natural accommodative process with its flexible haptics and placement within the capsular bag, enabling it to change power under control of the ciliary muscle. The Crystalens can render good distance vision and reduced visual disturbances compared to multifocal IOLs. New accommodative designs are under development as well.
“The reliable Crystalens AO platform is now in the new monofocal MX60E and MX60ET platforms that provides me with confidence for my outcomes and enhances my efficiency in the OR — particularly with my femtosecond laser procedures,” says P. Dee Stephenson, MD. “I love the lens design with its aspheric optic, constant power from center to edge and no induced spherical aberration. Plus these IOLs are scratch-resistant, glistening-free and have extended contact of the haptics in the bag at 110° for better stability and a more predictable outcome.” Dr. Stephenson is president of the American Board of Eye Surgery and Stephenson Eye Associates in Venice, Fla.
She notes that, due to the number of postrefractive surgery patients she treats, the aspheric design is her first choice to deliver premium vision with increased depth of field, giving great intermediate vision.
“The Bausch + Lomb platform helps me achieve more predictable and repeatable refractive outcomes in a broad patient population. I know I can get patients to their best potential vision quality with enhanced contrast sensitivity using this technology,” Dr. Stephenson says.
Small-aperture IOLs rely on a pinhole that permits only centrally focused light to hit the retina, thereby eliminating scattered peripheral light that can interfere with acuity. They tend to extend the depth of focus without blurred transitions but may result in contrast reduction, range-of-vision inconsistencies and visual effects. Suited to general cataract patients, a small-aperture IOL can also be ideal for a patient with a damaged iris, keratoconus or particularly difficult cataracts. Because the pinhole itself creates the depth of focus, small-aperture lenses have an inherent advantage over other multifocals in this area.
The IC-8 by AcuFocus is available outside the United States and currently undergoing FDA clinical testing. The XtraFocus Pinhole Implant (Morcher, developed with Claudio Trindade, MD) functions the same way using an even smaller pinhole. It earned a CE mark in 2016.
The toric lens is the only IOL that can decrease astigmatism after cataract surgery. Because astigmatism is caused by an asymmetry in the power of the eye, torics are designed with different lens medians having different powers. Once implanted in the eye, the surgeon rotates the lens to align it for proper astigmatism correction. If the measurements, power calculation and lens choice are spot on, the procedure will likely succeed. Prior to the advent of toric IOLs, the only way to correct for postop astigmatism without external lenses was with limbal relaxing incisions made during the cataract surgical procedure. The result of such corneal incisions is difficult to predict and not completely effective.
The previously mentioned manufacturers also offer toric versions of their presbyopia-correcting technology platforms.
Johnson & Johnson Vision recently released its updated Tecnis Toric II IOL platform that touts new haptics with increased friction that the company says enhances the implant’s ability to stay in place. The AcrySof IQ Toric IOL (Alcon) also features exceptional rotational stability in a wide range of correction powers. In addition, Bausch + Lomb’s enVista delivers stability and visual clarity owing to its glistening-free performance.
From lenses to implantation techniques
New IOL designs are at various stages in the development pipeline, and physicians are hopeful these lenses will help them to increase patient satisfaction and improve on earlier technologies. Likewise, techniques to manage IOL implantation continue to progress, including even where to best place the IOL.
An accommodative lens designed to be placed in the sulcus rather than inside the capsular bag, the Lumina by Akkolens, has shown early promise. Studies show restored postoperative vision, contrast sensitivity and accommodation.5 A CE mark is in development.
Accomodative IOLs 2.0
Future design strategies rely more on shape-related changes in the surfaces of IOLs or dynamic changes in refractive index.
IOLs like the Juvene (LensGen), a modular, fluid-optic accommodating IOL that is currently in trials outside the United States, has a dual optic that completely fills the capsular bag, preventing its contraction and posterior capsule opacification while harnessing as much natural ciliary muscle function as possible.
Inside the United States, a trial is underway of the investigational device FluidVision (PowerVision) that achieves accommodation through fluid changing the IOL’s shape based on movement of the ciliary body. OM
Drs. Berdahl, Farid, Stephenson and Thompson each have financial interest in the technologies they discuss.
- Zvorniĉanin J, Zvorniĉanin E. Premium intraocular lenses: The past, present and future. J Curr Ophthalmol. 2018;30:287-296.
- Alcon introduces AcrySof IQ PanOptix trifocal IOL in the U.S., the first and only FDA-approved trifocal lens. Aug. 27, 2019. https://www.alcon.com/media-release/alcon-introduces-acrysofiq-panoptix-trifocal-iol-us-first-and-only-fda-approved . Accessed Dec. 5, 2019.
- TECNIS Symfony DFU. https://www.jnjvisionpro.com/products/tecnis-symfony-iol . Accessed Dec. 10, 2019.
- DOF2015CT0020 Symfony MTF versus competition. https://www.escrs.org/vienna2018/programme/poster-village-details.asp?id=31778 . Accessed Dec. 10, 2019.
- Alio JL, Simonov A, Plaza-Puche AB, et al. Visual outcomes and accommodative response of the Lumina accommodative intraocular lens. Am J Ophthalmol. 2016;164:37-48.