Pushing the Limits of IOLs
Improving technology to reach visual targets. Dermot McGrath reports.
Surgeons and their patients can look forward to further improvements to intraocular lens (IOL) technology— new designs and materials should deliver enhanced visual outcomes in the near future, according to Ehud Assia MD.
“There are two IOL technologies in particular that I think we will see more of in the future. One is reshaping implanted lenses, and the second is using artificial intelligence to create innovative lens designs,” he said.
Reshaping implanted lenses, Prof Assia said, is a compelling strategy to tackle the recurrent problem of refractive surprise after IOL implantation.
“Today we are somewhere between 75% and 85% of cases within 0.5 D of target refraction and 94% within 1.0 D. But these refractive errors and surprises will always occur. A logical way to improve the accuracy is to implant the IOL first, wait until it stabilises, and only then reshape the IOL in terms of sphericity, toric, and multifocal components,” he said.
One way to achieve this is the approach used by the Light Adjustable Lens (LAL, RxSight) in which UV radiation is delivered to the lens after implantation. This affects the light-sensitive silicon macromeres and changes the optic’s shape and power, Prof Assia explained.
“The optic is changed to the required refraction and then locked in. The manufacturer claims to have 98% of patients within 0.5 D of target refraction,” he said.
Another interesting approach is Refractive Index Shaping (RIS) used by Perfect Lens, which uses a femtosecond laser to modify the refraction of the implanted lens.
“The laser performs an in-vivo modification of the lens refraction by altering the hydrophilicity of the lens’ polymeric material, producing a lens within the IOL. One can use any standard IOL with hydrophilic or hydrophobic material. The procedure can be repeated and corrected or reversed by using opposite patterns, so you can change the optics several times with the same lens,” he said.
Artificial intelligence—which is already impacting ophthalmology in areas such as big data collection and analysis, diagnostics, and imaging—will also make increasing inroads into IOL design.
“When engineers design a product, they define the ‘what’ and the ‘how’ one step at a time,” Prof Assia said. “For example, to create a bifocal lens, they start with a refractive base, add a diffractive element, and combine them to create a diffractive bifocal lens. With AI, however, the computer can process multiple variables and thousands of options in terms of materials, designs, parameters, optical qualities, and so on—and then come up with a design we never thought of before. With AI, the engineer just needs to define the ‘what’ and leave the ‘how’ aspect to the computer.”
Lens manufacturers have employed a wide variety of approaches to improve current trifocal designs, including refraction optics (Precizon Presbyopic NVA, Ophtec) and sinusoidal optics (Acriva Trinova IOL, VSY Biotechnology), to try to reduce the light dispersion. Another novel approach adopted in the Intensity IOL range (Hanita Lenses) uses a Dynamic Light Utilization (DLU) algorithm to maximise energy and ensure a continuous defocus curve at all distances.
Other techniques to improve trifocal lenses include using a mix-and-match approach, using a refractive lens in one eye and a diffractive IOL in the fellow eye, or combining two or more technologies in a single IOL. Modifying the chromatic or spherical aberration, and employing a pinhole effect, can also increase depth of focus and enhance performance, Prof Assia added.
Prof Assia presented at the 40th Congress of the ESCRS in Milan.
Ehud Assia MD is a Professor of Ophthalmology at Tel Aviv University and Medical Director of Ein-Tal Eye Center, Tel Aviv, Israel, and Former Director of the Department of Ophthalmology and Director of the Center for Applied Eye Research at the Meir Medical Center, Kfar-Saba, Israel. email@example.com
Thursday, December 1, 2022