Functional results and photic phenomena with new extended-depth-of-focus intraocular Lens

In recent years, multifocal intraocular lenses (MIOLs) were developed for patients who do not want to wear spectacles when using a desktop computer or mobile phone. The lenses either have a low to moderate addition for intermediate distances or are trifocal with an additional intermediate focus [1‐3].

Trifocal IOLs deliver good functional vision at different focal planes to achieve spectacle independence [4‐8]. A new development is extended-depth-of-focus IOLs (EDOF-IOLs), that aim to provide a continuous range of vision instead of multiple distinct foci. The first EDOF-IOL was the Tecnis Symfony (Abbott Medical Optics, Abbott Park, NY, USA), combining an apodized-diffractive surface with an echelette-design. Initial clinical results appear promising [9‐13].

A considerable disadvantage of diffractive designs is loss in contrast sensitivity due to reduced effective light energy reaching each focal plane. Perception of halos and glare, is another side-effect: arising from superposition of multiple images on the retina [14, 15]. Patient dissatisfaction can occur despite the functional visual results achieved.

An optical design not primarily based on diffraction ought to minimize these disadvantages. We examined the clinical outcomes with the Mini WELL Ready (SIFI, Catania, Italy), a new EDOF-IOL that relies on spherical aberrations of opposite signs to create an elongated focus. Standard visual acuity was tested using charts for predefined distances and an electronic reading desk was used for visual acuity assessment at individually chosen distances [16, 17]. Furthermore, contrast sensitivity as well as subjective perception of glare and halos were assessed to further characterize the clinical performance.

The Mini WELL Ready EDOF IOL showed good visual acuity outcomes that are consistent with that of IOLs such as the Tecnis Symfony.

Comparison of the two lenses is not easy because there are wide differences in the examinations performed in published reports on Symfony. Pedrotti et al. describe mean monocular UDVA, UIVA (60 cm) and UNVA values of 0.08 ± 0.12logMAR, 0.24 ± 0.11logMAR and 0.27 ± 0.11logMAR (50 eyes of 25 patients, 3 month follow-up) [12]. Kaymak et al. found a mean monocular UDVA, UIVA (70 cm) and UNVA of 0.02 ± 0.09logMAR, − 0.05 ± 0.08logMAR and 0.33 ± 0.12logMAR (36 eyes of 18 patients, 3 month follow-up) [11]. From other studies, only binocular visual acuity values are available: Ruiz-Mesa et al. report mean binocular UDVA, UIVA and UNVA values of 0.01 ± 0.02logMAR, 0.09 ± 0.08logMAR and 0.17 ± 0.06logMAR for this IOL (20 patients, 1 year follow-up) [13]. Similarly, Cochener et al. found a mean binocular UDVA, UIVA and UNVA of 0.03 ± 0.09logMAR, 0.13 ± 0.16logMAR and 0.21 ± 0.16logMAR (299 patients in the non-monovision group, 4–6 month follow-up) [9].

Our results are generally comparable to those of the aforementioned studies. Median UDVA was 0.13logMAR, perhaps attributable to residual refractive error and a non-optimized A-constant since it was fully-correctable by spectacles (median CDVA − 0.01logMAR). The Mini-Well performed even slightly better at intermediate and near distances with a median UIVA (80 cm) and UNVA of − 0.05 and 0.14logMAR respectively. Similar results were also observed in a multicenter study by Savini et al., who reported an enhanced depth of vision through 2.0 D of defocus, with the best performance at 1.0 and 1.5 D [20].

Our findings also appear to conform with laboratory observations. On the optical bench, Gatinel et al. showed the Symfony behaves rather like a bifocal IOL with a low add power [10], whereas Domínguez-Vicent found the Mini WELL has a broad depth of focus in the intermediate to near vergence [21]. This is also revealed by the defocus curve of the Mini WELL that shows a broad plateau of functional vision overlapping more than 4 diopters of defocus.

For patients seeking spectacle independence in most of everyday activities, the alternative to an EDOF-IOL is a trifocal IOL. All the latest trifocal IOLs use diffractive optics to generate three distinct foci for far, intermediate and near vision. For the AcrySof Panoptix IOL (Alcon Laboratories, Ft. Worth, TX, USA) Lawless et al. report initial results for monocular UDVA, UIVA (60 cm) and UNVA of 0.01 ± 0.10logMAR, 0.30 ± 0.14logMAR and 0.18 ± 0.10logMAR (66 eyes of 33 patients, 6 weeks follow-up) [7] (Table 3). In a comparison of two trifocal IOL designs in 10,084 eyes of 5042 patients, Bilbao-Calabuig et al. reported monocular UDVA, UIVA (80 cm) and UNVA (40 cm) outcomes of 0.04 ± 0.08logMAR, 0.00 ± 0.17logMAR and 0.07 ± 0.10logMAR for the AT Lisa tri 839MP (Carl Zeiss AG, Jena, Germany) and 0.06 ± 0.08logMAR, − 0.01 ± 0.15logMAR and 0.08 ± 0.10logMAR for the FineVision Micro F IOL (PhysIOL, Liege, Belgium) respectively (3 month follow-up) [4]. Other studies showed similar results for these two IOLs [6, 23, 25]. However, it should not be overlooked, that initial studies with the same IOL models in smaller patient cohorts showed different results: Sheppard et al. reported a monocular UDVA of 0.19 ± 0.09 for the FineVision IOL (30 eyes of 15 patients, 2 month follow-up) [22] and Alió et al. found monocular UDVA, UIVA (80 cm) and UNVA (40 cm) values of 0.18 ± 0.13logMAR, 0.20 ± 0.11logMAR and 0.26 ± 0.15logMAR for the same IOL model (40 eyes of 20 patients, 6 month follow-up) [5]. Similarly, for the AT Lisa trifocal IOL Mojzis et al. recorded UDVA, UIVA (66 cm) and UNVA (33 cm) results of − 0.03 ± 0.09logMAR, 0.08 ± 0.10logMAR and 0.20 ± 0.12logMAR (60 eyes of 30 patients, 6 months follow-up) [24], Kretz et al. report a monocular UDVA, UIVA (80 cm) and UNVA (40 cm) of 0.10logMAR, 0.15logMAR and 0.10logMAR (76 eyes of 38 patients, 3 months follow-up) [26] and Mendicute et al. report a binocular UDVA, UIVA (80 cm) and UNVA (40 cm) of 0.03 ± 0.09logMAR, 0.10 ± 0.15logMAR and 0.15 ± 0.14logMAR (104 patients, 3 months follow-up) [8].

Few studies have explicitly examined reading performance after MIOL implantation [18, 19, 27‐29]. The Salzburg Reading Desk measures reading acuity under close-to real-life conditions with simultaneous and continuous measurement of parameters, such as the patient’s distance from the screen, reading speed, smallest readable letter size and reading acuity. Using this device Attia et al. recorded median binocular uncorrected and distance-corrected reading acuities of 0.18logMAR at intermediate distance (80 cm) and of 0.05logMAR and 0.01logMAR at near distance (40 cm) with AcrySof Restor, (Alcon, Laboratories, Ft. Worth, TX, USA) a diffractive bifocal IOL with + 3.0 D near addition [18]., For Lentis MPlus, (Oculentis GmbH, Berlin, Germany), a rotationally asymmetric bifocal IOL with a + 3.0 D near addition, Linz et al. found median monocular uncorrected and distance-corrected reading acuities of 0.30logMAR and 0.18logMAR for intermediate distance (80 cm) and of 0.18logMAR for near distance (40 cm) [19]. With the diffractive trifocal FineVision IOL, Attia et al. reported median binocular uncorrected and distance-corrected reading acuities of 0.10logMAR and 0.11logMAR for intermediate distance (80 cm) and of 0.11logMAR and 0.01logMAR for near distance (40 cm) [30]. We found Mini Well reading performance at intermediate distance is comparable to that of the FineVision IOL and better than that of bifocal IOLs. The same is true for uncorrected near reading acuity. With the trifocal IOL, on the other hand, patients achieved a better distance-corrected near reading acuity.

Photic phenomena are an intrinsic problem with all MIOLs since the diversion of light to different foci unavoidably causes superposition of multiple images on the retina [10, 31, 32]. All diffractive IOLs are known to cause Halos to some extent, especially Starbursts [14]. The Mini WELL should cause less dysphotopsia since it does not rely on diffractive optics. However, assessment of photic phenomena is difficult and highly depends on the inquiry technique. Mendicute et al. correctly observed that the outcome of these questionnaires may vary according to whether one asks open or closed questions [8]. Indeed, if patients were not at all specifically asked for photic phenomena, the amount reported would be much lower. It is therefore difficult to compare across different studies the significance of photic phenomena attributable to a given IOL. In inquiries that only used undirected questions (‘Do you experience any difficulties with your vision’) the incidence of dysphotopsia reported was low [9]. Explicitly asking for different types of photic phenomena yielded higher numbers [8]. Although several studies report high patient satisfaction and low incidence of halos and glare, dysphotopsia remains a major complaint among patients who are dissatisfied after MIOL implantation [33‐35].

We used a computer-based simulator to assess perception of Halos and Glare, one which our group has experience of in studying trifocal IOLs [36]. We found the patients with the Mini WELL were mildly or not at all disturbed by Halos and Starbursts in daily life. However, we still regard this simulator as exploratory and so far, we restrained our analysis to being solely descriptive.

The clinical results reported herein should be considered in the light of some limitations, such as the limited number of patients enrolled or the lack of a control group. Future studies should also evaluate the Mini WELL IOL’s clinical performance with a longer follow-up period.

Previous clinical and laboratory studies, which directly compared EDOF-IOLs and Trifocal lenses, concluded EDOF-IOLs provide good far and intermediate visual results but fall short of trifocal IOLs for near visual acuity at common reading distances [10, 13]. Our results suggest the Mini WELL is different, showing good near visual acuity in addition to very good intermediate distance visual acuity. Laboratory observations support this finding [21]. In general, the Mini WELL renders a level of visual rehabilitation similar to that of current trifocal IOLs. Overall perception of dysphotopsia is lower and less severe than in comparable IOLs. These results should be confirmed with increased patient numbers and longer follow-up periods.