Introduction
Today, patients increasingly expect excellent vision, not only for distance but also for intermediate and near distances, as many everyday tasks require this range of vision (computers, tablets, smartphones, reading monitors, operating vending machines or driving). Standard, monofocal intraocular lenses usually provide excellent uncorrected visual acuity for distance (UDVA), while the patient may achieve good intermediate and near visual acuity only with the help of spectacles. In the last decade, the number of presbyopia-correcting lenses (multifocal, refractive, diffractive, pinhole) has increased significantly in order to achieve spectacle independence even at near distance. However, the use of these premium lenses is not possible and reasonable in every individual case (possible side effects, costs).
Enhanced monofocal intraocular lenses (IOLs) represent a relatively new type of lens on the market, which should lead to an additional intermediate vision at up to 80 cm while retaining very good distance vision, without increasing the risk for photic phenomena [
1‐
3]. These lenses must be distinguished from the classic enhanced depth of focus (EDoF) intraocular lenses, since the focus here is in a different range. In addition to choosing the optical principle, the surgeon has the task of selecting the fitting/best material. Currently, regarding market surveys, hydrophobic acrylic lenses are implanted most frequently, followed by hydrophilic acrylic IOLs [
4].
As a result of the problem of calcification of some hydrophilic IOL materials in the past, there has recently been a kind of witch hunt against hydrophilic acrylic lenses. Recently, this was put into perspective in a review paper and with presentations by Auffarth and LaHood, stating the safety and state-of-the-art status of hydrophilic material and the possible advantages of hydrophilic lenses [
5]. There are currently no uniform guidelines for the selection of hydrophilic or hydrophobic materials. Various secondary diagnoses have been discussed in the past, where the selection may play a role, like corneal dystrophy (Fuchs), endothelial grafts, diabetes, uveitis or pseudoexfoliation syndrome. Table
1 lists some of the stated advantages and disadvantages of IOL materials gathered from various publications [
6‐
15].
Table 1
Possible advantages and disadvantages of available IOL materials
PMMA | Good biocompatibility Low aqueous flare Low rate of inflammatory cell accumulation on lens surface | Rigid, not foldable Large incision size, astigmatism High rate of PCO |
Silicone | Low rate of inflammatory cell accumulation on lens surface Low rate of PCO | Higher rate of fibrotic reaction Lens surface opacification due to contact with intravitreal air |
Hydrophilic acrylic | Good biocompatibility due to high water content Low aqueous flare Low rate of inflammatory cell accumulation on lens surface Flexible/soft for smallest incision sizes | Higher rate of PCO + ACO Insufficient sharp-edged design due to water content Greater lens epithelial cell growth on lens surface Calcification may occur |
Hydrophobic acrylic | Lower rate of PCO + ACO Posterior sharp-edged design compatible Lower rate of lens epithelial cell growth on lens surface | Higher aqueous flare More inflammatory cell accumulation on lens surface Glistenings may occur |
Therefore, it is not possible to establish a purely scientific ranking of these materials. Both hydrophobic acrylate and hydrophilic acrylate materials in various models from different companies have proven their safety in scientific studies and in clinical practice. Problems like glistenings or calcifications have remained relatively rare side effects so far. The choice should be made individually and selected for each individual case.
The aim of this clinical observational study was to directly compare two different IOL platforms with the same enhanced monofocal optic but with different material (hydrophobic acrylate versus hydrophilic acrylate) and different haptic design in clinical routine.
The data was collected as part of a registry study, registered at clinicaltrials.gov under the registration number NCT05290870. The study adhered to the tenets of the Declaration of Helsinki and all patients gave their informed consent to participate in this study and for data about their case to be published. As all used devices/implants were already CE marked and the procedures followed the standard regime, no approval from an ethics board committee was required for this clinical observation.
Discussion
Laboratory Experiments
The L-333 IOL was recently analysed in an optical bench study [
16]. The laboratory study investigated the enhanced monofocal IOL (L-333) and the monofocal counterpart (L-313), using OptiSpheric IOL PRO2 (Trioptics, Germany) in order to assess the optical quality according to ISO standards. The two IOLs were evaluated through frequency modulation transfer function (MTF), Strehl ratio (SR) and focus MTF at 50/lp/mm using a 3.0-mm and a 4.5-mm aperture. Tilt and decentration were also measured and wavefront measurements were obtained using WaveMaster IOL 2 (Trioptics, Germany). The study confirmed some enlarged depth of focus of the L-333 by combining spherical aberration of different order and opposite sign. The enhanced monofocal Lentis Quantum performed very well even with large aperture sizes, indicating that the lens could also be a good option in refractive procedures in younger patients (with wide pupils). Moreover, the L-333 showed a kind of tolerance to decentration and tilt due to its optical design compared to typical multifocal (diffractive, high add) IOLs. Nevertheless, the L-333 as an enhanced monofocal IOL should be very clearly differentiated from a typical multifocal IOL as the focus is in a different range. A clear distinction should also be made from typical EDoF IOLs like the Lentis Comfort (LS-313 MF15, Teleon Surgical) as these EDoF IOLs have a higher near addition of 1.5 D and therefore better UIVA performance at intermediate distances up to 60 cm. Interesting possibilities would also be a kind of mix/match selection of different optic designs (EDoF and enhanced monofocal) in the future.
Another laboratory study objectively analysed the hydrophobic enhanced monofocal ACUNEX Quantum (AN6Q) and compared it with the monofocal ACUNEX AN6 [
17]. The results confirmed that the ACUNEX AN6 can provide a sharp contrast and distinct image focus, while the enhanced monofocal AN6Q provided an extended range of focus with only a minor, neglectable decrease in contrast quality. The study showed that the AN6Q effectively generates the depth of focus by combining spherical aberration (Z 4–0) and secondary spherical aberration (Z 6–0) of opposite sign.
In the scope of the registry study, all performance measures showed a satisfying outcome. In the case of SE, only group B (AN6Q) showed a significant improvement after implantation. However, the post-op standard deviation of SE for group A (L-333) was much smaller (0.24 D) than pre-op SE (2.86 D), indicating that most of the patients improved, nonetheless. The bigger standard deviation of post-op SE for group B compared to group A is worth noting as it might be explained by the different haptics used for the models. The C-loop design of the AN6Q could be slightly less stable than the plate-haptic design of the L-333 in the first postoperative period, resulting in a slightly higher standard deviation for the AN6Q. Significant improvements in all groups were found regarding distance visual acuity outcomes, both uncorrected and corrected with excellent post-op performance and a very low standard deviation.
Outside the scope of the prospective registry study, Radner reading table No. 4 and the Radner-Götlinger reading table were used to assess near visual acuity monocularly at 80 cm distance at 1 month post-op [
18]. The results are given in Reading Acuity Determination (logRAD) and are equivalent to the distance acuity in logMAR. Out of the 51 eyes of group A, 41 (80%) reached line 5 (0.0 logRAD) with fewer than one mistake, 5 eyes (10%) reached line 4 (− 0.1 logRAD) and the remaining 5 eyes were below line 5. For group B, 38 eyes of the 51 in total (74%) reached line 5 with fewer than one mistake, 2 eyes (4%) reached line 4 and 11 eyes (22%) reached line 6. These results are consistent with the high overall satisfaction in the survey. It must be emphasized that only monocular vision for intermediate range was tested here, and that further improvement could be achieved by testing binocular vision for reading at 70–80 cm. However, this was not the subject of this study. It will be assessed in further evaluations and long-term observations.
Hydrophilic vs Hydrophobic
Teleon offers lenses on hydrophilic and hydrophobic platforms with various different optics. This fact makes it possible for the surgeon to choose the best option in the individual case or to follow a mix and match concept; this seems important to achieve high patient satisfaction. It is currently not scientifically clear which haptic concept (C-loop versus plate haptic) and which material properties and water content (phob vs phil) are fundamentally better, as there are advantages and disadvantages to both. In our study, there was a slight indication that the C-loop haptic of AN6Q was less stable and resulted in a slightly higher standard deviation of SE than the plate-haptic design of L-333. But further evaluations with higher numbers of cases are necessary. There was a different behaviour of the tested IOLs during implantation and unfolding due to material properties (water content) and also shape/design. However, no advantages and disadvantages could be scientifically documented because no complications occurred in all cases (n = 102). The unfolding behaviour and speed of unfolding were slightly different as a result of material properties of the hydrophilic and the hydrophobic IOLs, but might play a minor role.
Limitations of This Study
The follow-up period in this registry study is relatively short. The main goal of this evaluation was to provide initial clinical data and verify if the lens is safe and shows good postoperative results. Lens models with different optics but the same material and haptic design have been implanted in clinical routine many times and have been observed over a long period of time and proved their safety in clinical routine and in studies [
19‐
21]. The aim of the present manuscript is to provide first clinical data for a new variant of a monofocal lens and discuss the optic design and laboratory results of the optical bench analysis. Further in-depth studies (multicentre, high numbers of cases) and direct comparisons to standard monofocal IOLs, EDoF and premium lenses (diffractive, refractive) are necessary.
Enhanced Monofocal Optic Design
This relatively new group of lenses (called enhanced monofocals) seems to be another interesting step to meet the individual needs of patients with cataracts. Other manufacturers also offer IOLs that can be counted in this category, e.g. Eyhance (Johnson & Johnson Vision), LuxSmart (Bausch & Lomb), Isopure (BVI), Vivinex Impress (Hoya Surgical) and IC-8 (AcuFocus). It is important to emphasize that these enhanced monofocal lenses should not claim to be “spectacle-free” and should therefore not be included in the group of typical “premium refractive lenses”. These IOLs are monofocal lenses that aim to offer additional advantages without increasing the risk of disadvantages and could therefore represent a good further alternative in the standard care of patients with cataracts.