New IOL technologies
There may be many paths forward, though technical challenges remain.
MK Raheja PhD, Jan Willem de Cler and Julian Stevens MRCP, FRCS, FRCOphth, speaking at the Ophthalmology Futures Forum in Vienna
Multiple intraocular lens (IOL) technologies, including multifocal, EDOF, adjustable, and both mechanical and electronic accommodating lenses, will continue developing over the next few years as industry and ocular surgeons seek better treatments for presbyopia, according to presenters at the Ophthalmology Futures Forum
However, designing IOLs that provide reliable and durable presbyopia correction remains daunting, said Julian Stevens MRCP, FRCS, FRCOphth, DO of Moorfields Eye Hospital. He noted that accommodating mechanical and flexible gel lens IOL designs that rely on ciliary contraction to physically move or reshape lenses often lose accommodative range as capsules contract and stiffen over time due to fibrosis.
Similarly, lens implants can develop long-term unpredictable change with shift in position, and recently for one manufacturer mineralisation developing as much as five years after surgery. This severely degrades multifocal performance and makes lens exchange extremely difficult, particularly following posterior capsulotomy, Dr Stevens said. Attempts to induce multifocality in adjustable lenses after implantation can result in optical complexities and optical irregularity, which is challenging for patients and very difficult to correct, he added.
Detecting such problems lengthens development time, but is necessary, Dr Stevens said. “Given that we are implanting these lenses in younger and younger people for refractive reasons, how long would you like to see outcomes data? Forget the regulations, in the real world what do we need for safety and efficacy? How many years do you wait before you say ‘yes, that’s good enough’?” There should be a European database for long-term follow-up at 10, 15 and 20 years and beyond, he believes.
How much development time is needed depends on the technology, said MK Raheja PhD, head of ophthalmic implants R&D for Johnson & Johnson Vision. Mechanical accommodating designs rely on performance of the capsular bag and ciliary muscles, which can deteriorate with time and therefore require more time to demonstrate efficacy. Multifocal, EDOF and adjustable lens technology involves optical trade-offs that may be more acceptable for some patients than others, and this takes time to assess. “We need to better understand patient needs as well as physiology of their eye to increase the probability of success with the presbyopia solution that we provide”.
Laurent Attias, senior vice president for corporate development at Alcon, sees merit in continuing development of light-splitting, accommodating and adjustable lenses. “Each has its own challenges,” he said. Multifocals must balance a mix of near, intermediate and far vision while minimising dysphotopsias, mechanical accommodating lenses must preserve an acceptable range of movement and the precision and long-term safety of adjustable lenses must be proven. “The good news is each are viable routes toward the same golden egg called presbyopia.”
Dr Stevens believes electronic accommodating IOLs that adjust refractive power by varying lens refractive index will be an attractive solution. However, battery technology must improve to provide a 40-to-50-year lifespan with enough energy density to be light enough to implant. “Once that comes in it will be a total game-changer,” he said. However, any electronic lens implant will not be compatible with MRI scanning, and this will likely be a serious drawback.
Alcon is making progress on electronic accommodating IOLs and contact lenses, Attias said. “The battery technology is not that far off… we’ve seen [lifespan] improvements from four years to 20 years.”
Rapid progress is also being made on other issues that will make electronic accommodating lenses usable. These include managing the speed and precision of accommodation, which are critical to patient acceptance, and developing foldable electronics that will enable insertion accommodating IOLs through monofocal-size incisions of 2.5mm or so.
In fact, Attias sees electronic accommodating IOLs pulling ahead of contact lenses due to the challenges of keeping contacts comfortable. “Unless you solve for comfort, nothing else matters.”
Raheja believes that future presbyopic IOL solutions may combine approaches. Every technology has its advantages and limits and all are at an early stage, he said. “We need to push forward on every front.”
According to Carl Zeiss Meditec, another critical factor in boosting acceptance of presbyopia-correcting lenses is providing diagnostics that support predictable patient outcomes. The company reports that it is very important not to look at the IOL in isolation as it is also a process of diagnostics, using information to perfect the technique so the end result is what is expected.
Failing to recognise this can lead to the avoidance of prescribing presbyopia-correcting IOLs not because of any problem with the lens itself, but a lack of knowing how to implant it accurately.
Attias agreed. Even today’s toric lenses require extra time and skill to implant, and this becomes a barrier to use. “We need to simplify using [presbyopia-correcting IOLs] and simplification will take time. We are counting on the early adopters to demonstrate the concepts.”
Dr Stevens said lenses optimised to fit into a precision-cut anterior capsulotomy are a step toward increasing success because they allow centring the lens precisely and permanently on the visual axis. “You don’t have lateral movement and you don’t have decentration.” He believes that optimising lens design to take advantage of the potential precision offered by femtosecond laser technology will eventually increase use of presbyopia-correcting and other speciality lenses.