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Enhanced monofocals may encourage presbyopia correction in cataract patients. Roibeárd O’hÉineacháin reports
Arange of new enhanced monofocal intraocular lenses (IOLs) may provide a more attractive option than multifocal IOLs to presbyopic and cataract patients who desire increased spectacle independence without loss of visual quality or disturbing photic phenomena.
“The industry is really working very hard at getting rid of dysphotopsias and improving intermediate vision and enhanced optical quality. We need to understand patient needs and educate them [on] the compromises they may need to make but also show them they can get quite a lot out of these new lenses nowadays,” Professor Gerd U Auffarth MD, PhD, FEBO told an ESCRS symposium.
Prof Auffarth noted that according to the ESCRS 2020 clinical practice survey, presbyopic IOLs represent only 8–10% of IOLs currently implanted. In addition, among respondents to the ESCRS 2021 clinical practice survey, 38% cited loss of contrast visual acuity and 52% cited concerns over problems with nighttime visual quality as reasons for their reluctance to implant presbyopia-correcting IOLs.
The problem with the older, multifocal presbyopia-correcting IOLs is they have two distinct peaks of focus, so a near-focused distant light source creates a halo around the distance-focused image in scotopic conditions. The size and intensity of the halos depend on the degree of difference between the two focal points. However, extended depth of focus lenses (EDOF) do not have two distinct foci.
ENHANCED MONOFOCAL IOLS Recent years have seen the introduction of enhanced monofocal IOLs. These use different optical principles, such as induced high asphericity or complex polynomial surface designs to maintain the reliable uncorrected distance visual acuity (UCDVA) and low dysphotopsia rates of monofocal IOLs while increasing the depth of focus for improved functional intermediate vision.
“We more or less have to balance out certain things to maximise quality of vision. We can add just a tiny bit of bifocality or depth of focus because we don’t want to decrease quality of vision or increase night vision symptoms. But there is always a certain range that we can take advantage of and give some positive impact on our patients,” Prof Auffarth said.
The first of these new lenses to enter the market is the Tecnis® Eyhance ICB00 (Johnson & Johnson Vision). The IOL is identical in design to the monofocal aspheric Tecnis ZCB00 in terms of basic dimensions and material. However, it differs in having a central, optical area with higher-order aspheric components that increase lens power.
An optical bench study showed the Eyhance has a depth of focus of around -1.0 D to -1.5 D. Researchers confirmed those findings in a multicentre study, which showed an increase of at least one line in intermediate vision and rates of halo, glare, or starbursts very comparable to standard monofocal IOLs.
Other manufacturers have also developed enhanced monofocal designs. One example is the IsoPure 1.2.3 (BVI/Physiol), which features anterior and posterior aspheric surfaces with high-order aspheric terms that extend its visual range compared to a monofocal IOL while maintaining a good far-focus performance. In optical bench tests, the IsoPure 1.2.3 lens performs as well as an aspheric monofocal IOL at defocus of 0.5 D to 0.0 D but exceeds the monofocal IOL’s performance at a defocus of -1.0 D to -1.5 D.
Another of the new enhanced monofocal IOLs, the RayOne EMV (Rayner), uses a totally different approach. This new IOL’s optic purposely induces positive spherical aberration to an increasing focus range even in the hyperopic direction. The lens is designed for use in a monovision setup, and optical bench testing shows that with a primary defocus of -1.0 D, it provides defocus up to -2.5 D.
NEW ADVANCED TRIFOCALS Several new trifocal lenses employ the EDOF concept for cataract patients who wish to have distance vision similar to monofocal IOLs while also having functional intermediate and near vision. Among these is the AcrySof® IQ Vivity™ ERV (Alcon), which uses a wavefront shaping to provide a very broad depth of focus with minimal dysphotopsias. In a randomised prospective trial, patients bilaterally implanted with the lens achieved an extended range of vision of 0.0 logMAR at distance, 0.1 logMAR at intermediate distance, 0.2 D logMAR at 50 cm, and 0.3 logMAR without any dysphotopsias.
There is also the new Tecnis Synergy™ IOL, a hybrid EDOF/ multifocal diffractive lens that combines the diffractive technology from Tecnis® Multifocal and Tecnis Symfony® IOLs with the correction of chromatic aberration to deliver continuous high-contrast vision across its range of focus. It also has a violet light filter to help reduce light-scatter. Similarly, another EDOF/ trifocal diffractive hybrid, the Finevision Triumf (BVI), aims to minimise the dysphotopsias by eliminating chromatic aberration and putting more power into the intermediate focus, Prof Auffarth said.
Dr Auffarth presented the information during a symposium at the ESCRS Virtual Winter Meeting 2022.
Gerd U Auffarth MD, PhD, FEBO works with the International Vision Correction Research Centre (IVCRC), The David J Apple International Laboratory for Ocular Pathology, University-Eye-Clinic Heidelberg, Germany. gerd.auffarth@med.uni-heidelberg.de