Will diffractive optics continue to be the mainstay for presbyopia correction?
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Diffractive lenses are not perfect but work
Twelve years ago at the AECOS meeting, a program chair asked the audience if in 10 years we would be able to achieve near vision for our cataract patients with lenses through accommodative technology or with diffractive technology.
Almost everyone raised their hand for accommodative lenses. Yet here we are today, more than 10 years later, and the dominant method to achieve presbyopia correction for our patients is still diffractive in nature. One of the reasons for this is that we have not figured out how to achieve pseudoaccommodation with lens technology in any way that is reliable or safe. It turns out there are just too many variables in play to make a functioning accommodative lens. Another reason is that diffractive technology works. It is not perfect, but it reliably works in almost everyone who chooses it for their eyes. In addition, advancements in diffractive optics have significantly reduced the side effects associated with early technology.
Currently, if a patient wants to be able to see in the distance and read a book binocularly after cataract surgery, the only option that can deliver that is through a diffractive lens. Will that change in the future? Possibly. But the fact remains that the more complex a technology is (and accommodating lenses currently in development are complex), the more unpredictable the results are. If the question I mentioned earlier were asked today, I have no doubt most surgeons would respond the same way, nor would I be surprised if I were able to reprint these words in response.
- For more information:
- Mark A. Kontos, MD, is a Healio | OSN Presbyopia Board Member.
Ophthalmologists will move away from diffractive lenses
I believe that we will eventually move away from diffractive optics toward other more advanced forms of extended depth of focus that better preserve quality of vision.
Diffractive optics always involve a compromise between quality and quantity of vision. They separate the light into segments, and any time we divide light, we lose image quality. Diffractive optics are also associated with side effects such as glare and halos. There are still many patients who do not notice the glare and halos and are perfectly happy with the compromises of these lenses, but trying to discern which patients will be more or less bothered by the side effects is difficult. Despite all the amazing preoperative technology we have for screening, there is a subjective aspect of patient tolerance that is still unpredictable. The uncertainty does not appeal to most of us, and this explains the still limited penetrance of this type of IOL. If you ask the average ophthalmologists whether they would choose diffractive optics for themselves, most of them would say no, and that is indicative of our future goals with cataract surgery.
We have had diffractive optics for 25 years, and they have improved significantly but have done so by decreasing the near add. When these lenses were initially introduced, we had a +4 D add, with a high degree of glare and halos. As we have gone down to a +3 D add and then +2.5 D add, we have seen the side effect profile improve.
Over the last few years, efforts have been made to find ways of increasing the range of vision with less compromise of quality. In 2017, extended depth of focus was officially defined as a new category of lenses by the American Academy of Ophthalmology, and optics that harness spherical aberrations, pinhole optics and zonal refractive technologies have pursued the common goal of increasing range of vision without dividing the light. Recently, the Light Adjustable Lens (RxSight) and the IC-8 Apthera IOL (Bausch + Lomb) have entered the market with good outcomes, and many ophthalmologists would choose one of those lenses for their own eyes. New shape-changing, bag-filling technologies are now on the horizon, and ultimately, the cure for the loss of accommodation will be the goal.
- For more information:
- Kendall E. Donaldson, MD, MS, is a Healio | OSN Technology Board Member.
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