Next-generation EDOF lenses: the choice is yours

Although we seem to have moved on light-years beyond the first intraocular lens (1949, Sir Harold Ridley), and millions of patients worldwide have benefitted from multifocal lenses providing a high degree of spectacle independence, there are still unmet needs. Vigorous research efforts world-wide are directed at improving quality of vision. 

I would like to share with you some of what I have learnt on the next-generation EDOF lenses. Over the past 18 months, I have implanted >500 Isopure? (PhysIOL), and also tested many others: Vivity? (Alcon), Tecnis Eyhance? (Johnson and Johnson), Luxsmart? (Bausch & Lomb), Synthesis+? (Cutting Edge).

Extended-depth-of-focus (EDOF)

We seem to be clearly moving away from IOLs that are "multifocal", referring to the splitting of light to distinct foci, to lenses that produce a single elongated focal point. EDOF lenses "extend the depth of field", thereby allowing a wider range of (uncorrected) vision, typically from distance to intermediate, with less visual side effects compared to multifocal IOLs.

All EDOF lenses are equal1, but some are more equal than others

The older diffractive-EDOF lenses such as AT Lara? (Zeiss) and Tecnis Symfony? (Johnson and Johnson) as well as some of the newer ones such as Tecnis Synergy? (Johnson and Johnson) still rely on multifocality to some extent. And therefore, by their very (diffractive) nature, they are not completely free of side effects.

Hence the unmet need and development of a next generation… of non-diffractive EDOF lenses without overlapping images. They can also be referred to as "pure" EDOF lenses2. By inducing spherical or other aberrations (e.g. Tecnis Eyhance?, Johnson and Johnson) or by means of a pinhole effect (e.g. IC-8?, AcuFocus Inc), incoming light waves are extended in a longitudinal plane. 

Non-pinhole, non-diffractive EDOF lenses, are also referred to as “monofocal PLUS IOL” or “enhanced monofocal IOL”, because they are designed to keep the benefits of a monofocal IOL and to add intermediate vision.

Company data and (sparse) clinical studies suggest that next-generation EDOFs have very low potential for glare and halos due to their novel design compared with diffractive technology3. Because they are not diffractive, these lenses could also theoretically benefit more patients: e.g., mild macular pathologies, mild glaucoma and less-than-perfect corneas.

Lessons from my own experience

1. Non-diffractive EDOF lenses are indeed very "easy" lenses: I have implanted them in eyes with mild macular disease and in eyes with an imperfect cornea (e.g., keratoconus). I have also used a mix-and-match approach in several patients who had previously had a monofocal IOL implanted in the other eye, and the results were very good. In addition, the EDOF effect creates a larger 'landing zone' and can help reduce the effects of refractive surprise, and I like implanting them in post-LASIK eyes.

2. I have consistently used mini-monovision (-0.25D to -0.5D) in all patients except in the presence of ocular morbidities such as early AMD or amblyopia. The gain in intermediate and even reading visual acuity clearly outweighs the small reduction in quality of binocular distance visual acuity.

3. I consider the EDOF lens as a full premium IOL, and act accordingly. This means, among other things, calculating the IOL power extremely carefully, repeating biometries and topographies to obtain high-quality measurements, operating on the steep axis, adjusting the size of the clear corneal incision to match the amount of astigmatism, and performing limbal relaxing incisions when necessary. In the absence of toric versions (at least for a reasonable dioptric range), I include eyes with astigmatism up to 1.5 diopters, and I try to reduce it with the above-mentioned measures.

4. Not all companies have completely solved their "ease of implantation" issues yet. Look at how lenses can get stuck in the tip of the cartridge (note the inadvertent "bulging" of the cartridge).

?Your choice

Companies are very active and every few months a new "next generation" EDOF lens comes on the market without much clinical data and with little to no publications. They all claim similar optical properties and clinical benefits, although the optical mechanisms seem to differ somewhat (almost incomprehensible to non-mathematicians anyway;-).

A key finding from my earlier work? ? is that strikingly similar lenses can behave completely differently. Even the smallest changes in design/material can have a major impact on the clinical properties of a lens. This will be no different with next-generation EDOF lenses, and it is certainly prudent to be wary and selective when it comes to 'picking the right lens'. It's not just about 'intermediate acuity', many other characteristics are worth looking at closely. Even 'trivial' factors such as ease of implantation can make the difference in daily practice. 

As long as the evidence from comparative clinical studies remains thin, clinicians will be guided mainly by their experience and open communication with colleagues when choosing the 'right EDOF lens' from the wide range available.

We are conducting a retrospective study in our own clinic and are about to start a prospective comparative study as well.

To be continued!

Kristof Vandekerckhove

1.     Special Report: American Academy of Ophthalmology Task Force Consensus Statement for Extended Depth of Focus Intraocular Lenses. Ophthalmology 2017 Jan;124(1):139-141 https://www.aaojournal.org/article/S0161-6420(16)31336-7/fulltext

2.     Extended Depth-of-Field Intraocular Lenses: An Update. Piotr Kanclerz, Francesca Toto, Andrzej Grzybowski, Jorge L Alio. Asia Pac J Ophthalmol (Phila). 2020 May-Jun; 9(3): 194–202.

3.      “Alcon Announces European Launch of Vivity, the Only Presbyopia-Correcting Intraocular Lens With X-WAVE Technology.” Alcon.com, 2020, www.alcon.com/media-release/alcon-announces-european-launch-vivity-only-presbyopia-correcting-intraocular-lens-x

4.     Rotational Stability of Monofocal and Trifocal Intraocular Toric Lenses With Identical Design and Material but Different Surface Treatment. Vandekerckhove K, J Refract Surg. 2018;34(2):84-91 https://journals.healio.com/doi/pdf/10.3928/1081597X-20171211-01

5.     Rotational stability of a new toric IOL, Kristof Vandekerckhove, ESCRS 2014, London. https://www.dhirubhai.net/in/kristof-vandekerckhove/detail/overlay-view/urn:li:fsd_profileTreasuryMedia:(ACoAACYhKnsBHa7O0tAs1tpoMgnTe8uiM9mqCCY,1635454934117)/