Comparative Analysis of the Clinical Outcomes of Two Toric Presbyopia-Correcting Intraocular Lenses

The presence of residual astigmatism after implantation of a multifocal intraocular lens (IOL) due to non-corrected pre-existing corneal astigmatism can lead to a clinically significant degradation of visual performance [1, 2], even when the magnitude of this astigmatism is low [3]. This can lead to the need for a corneal laser retreatment or even a piggyback implantation including a toric IOL to achieve a full refractive correction allowing a satisfactory visual rehabilitation across all distances [4]. Toric multifocal IOLs were developed to solve this situation, providing not only the visual restoration at all distances but also allowing a complete correction of the spherocylindrical error, avoiding or minimizing the presence of residual astigmatism [5].

Several studies have demonstrated the efficacy of toric multifocal IOLs to provide an efficacious correction of pre-existing corneal astigmatism while providing good visual acuity at different distances [6‐14]. Among them, diffractive trifocal IOLs are the most commonly used; they combine a toric surface with a diffractive one, which is normally equivalent to that used in the non-toric version of the IOL [6‐14]. Recently, a new toric multifocal IOL was developed by the manufacturer Johnson & Johnson that combines a diffractive-based extended depth of focus profile (EDOF) with a diffractive multifocal pattern, which is commercially known as Tecnis Synergy™ IOL [15]. This hybrid optical approach is efficacious for delivering a continuous high-contrast vision from far through near, even in low lighting conditions [15‐26]. To date, only De Rojas et al. [20] have evaluated the outcomes of this new toric presbyopia-correcting IOL, but in a subsample of 22 eyes implanted with the toric version of Tecnis Synergy™ from a total sample of 104 eyes implanted with the non-toric version. However, these authors did not provide a specific analysis of the efficacy of the astigmatic correction of the toric version of the IOL. The aim of the current study was to evaluate and compare the clinical outcomes of a trifocal diffractive toric IOL with those obtained with the toric version of this new diffractive-based IOL combining an EDOF and a multifocal pattern.

A total of 86 eyes of 51 patients with mean age of 59.2 years (SD 9.4, median 53.7, range 43–83 years) were enrolled. The sample comprised 29 men (56.9%) and 22 women (43.1%). A difference close to the limit of statistical significance among IOL groups was found in age (ATLISA vs Synergy groups: 56.3 ± 9.1 vs 50.8 ± 9.1, p = 0.049). In contrast, no significant differences between groups were found in sex distribution (p = 0.842). Table 1 summarizes the preoperative clinical data obtained in the IOL groups of the sample evaluated. As shown, no significant differences were found between groups in axial length (AXL), keratometry, anterior chamber depth (ACD) or IOL power (p ≥ 0.329).

The correction of pre-existing corneal astigmatism in eyes implanted with presbyopia-correcting toric IOLs is necessary to obtain a satisfactory visual outcome, especially at intermediate and near distances [1‐3]. It has been demonstrated that the effect of residual astigmatism on satisfaction was more evident at the 0.75 to 1.00 D level for eyes implanted with either monofocal or multifocal IOLs [29], with especially negative impact of residual astigmatism on intermediate vision with some trifocal IOLs [1]. In the current study, two different types of toric presbyopia-correcting IOLs have been evaluated and compared, a trifocal diffractive and an hybrid model combining a diffractive-based EDOF and a multifocal diffractive pattern, investigating not only the level of visual rehabilitation achieved with them, but also the efficacy of the refractive correction by vector analysis. It was confirmed that the two groups of eyes (each one implanted with one of the two IOLs evaluated) were comparable in terms of anatomical, visual and refractive parameters, with no significant differences existing between them preoperatively in any clinical parameters assessed.

The analysis of the visual outcomes measured with the two IOLs evaluated revealed that there were no significant differences in UDVA, UNVA or CDVA between IOL groups at 1, 3 and 6 months after surgery. Specifically, mean UDVA values of 0.02 ± 0.03 and 0.00 ± 0.01 logMAR were found at 6 months postoperatively in ATLISA and Synergy groups, respectively. Concerning UNVA, mean values of 0.01 ± 0.04 and 0.00 ± 0.00 logMAR were found in these two groups, respectively. The visual outcomes obtained in the ATLISA group were consistent with those reported by Paredes et al. [30] using an optimized preoperative and intraoperative protocol and with those reported by Kretz et al. [31]. In other studies [32‐34], somewhat poorer UNVAs have been reported with the AT LISA trifocal toric IOL, which can be attributed to several factors such as the procedure used for measuring the visual acuity (optotype used, illumination conditions, etc.), target refraction or age range of included patients. Concerning the Synergy group, the results were similar to those reported with the non-toric version of the IOL by some previous authors [15‐17, 19]. However, other authors have reported somewhat worse visual outcomes compared to those obtained in the current study when evaluating the clinical performance of the non-toric version of the Tecnis Synergy™ IOL [18, 23]. As previously mentioned, one of the critical factors for these discrepancies in the visual outcomes among clinical studies, which may be caused by the different methodologies used for characterizing such outcomes. Therefore, comparative studies between different modalities of IOLs using the same methodology as in the study reported here are necessary to extract more consistent conclusions about the clinical performance of presbyopia-correcting IOLs.

Besides the measurement of visual acuities under photopic conditions, a measurement of UNVA under mesopic conditions was performed, obtaining mean values of 0.16 ± 0.03 and 0.15 ± 0.04 logMAR at 6 months after surgery in ATLISA and Synergy groups, respectively. This difference did not reach statistical significance, demonstrating that both IOLs had a comparable performance under mesopic conditions when working at a distance of 40 cm. These results were comparable to those obtained for the non-toric version of the Tecnis Synergy™ IOL in previous studies [15, 16, 18, 20]. Our research group [15] reported a mean monocular mesopic UNVA measured at 40 cm of 0.14 ± 0.03 logMAR in a series of 103 patients with ages ranging from 35 to 75 years old and implanted with the Tecnis Synergy™ IOL.

The measurement of the defocus curve with the two models of IOL evaluated allowed determining the real visual performance achieved by patients implanted with them across all ranges of distances from near to far. In our series, better distance-corrected visual acuities were found in the Synergy group compared to ATLISA group for most of defocus levels, with the largest differences in the visual acuities corresponding to the defocus levels of − 1.50, − 3.00 and − 3.50 D. This suggests a better visual performance of the Tecnis Toric Synergy™ IOL compared to the AT LISA tri, especially for the closest distances. This is consistent with the results of previous studies evaluating the non-toric version of the hybrid IOL combining the EDOF and multifocal diffractive patterns in which a continuous range of vision was detected, with a visual acuity of 0.10 logMAR or better for the defocus levels between 0.50 and − 2.50 D [16, 17, 19, 22‐24]. In contrast, in our series, distance and near peaks in the defocus curve could be more clearly distinguished in eyes implanted with the trifocal IOL evaluated, with a reduction of visual acuity for the defocus level of − 1.50 D, but always maintaining the mean values > 0.20 logMAR. This is consistent with the defocus curve profile reported in previous studies evaluating the visual performance with the AT LISA tri toric IOL [11, 32].

The predictability of the refractive correction achieved with the two IOLs evaluated in the current study was high, with a residual sphere within ± 0.50 D in all cases, except in one eye of the Synergy group at 6 months, and a total of 100% and 96.2% of eyes in the AT LISA and Synergy groups with a postoperative manifest cylinder of ≤ 0.50 D at the end of the follow-up. This is consistent with the results of previous series evaluating the trifocal toric IOL [30] and the non-toric version of the hybrid IOL investigated [15‐26]. Our research group found that 99% of eyes had a spherical equivalent within ± 0.50 D in a sample of 206 eyes implanted with the non-toric version of the Tecnis Synergy™ IOL and De Rojas et al. [20] found that 88% of eyes had a SE within ± 0.50 D in a group of 52 patients implanted with the spherical or the toric version of the Tecnis Synergy™ IOL. All these results confirm that the A-constant for the AT LISA tri and Tecnis Toric Synergy™ IOLs has been optimized and appropriately defined.

The efficacy of the astigmatic correction with the two IOLs evaluated in the current study was high, with no significant differences between TIA and SIA and DV values very close to zero. Likewise, mean ME was very close to zero (AT LISA 0.04 ± 0.20 vs. Synergy − 0.04 ± 0.09, p = 0.05) with both IOLs, although differences were in the limit of statistical significance. This means that there was a slight trend to overcorrection with the trifocal IOL and a trend to undercorrection with the hybrid IOL. These differences may be attributed to differences in the algorithm used to estimate the cylinder power to implant, including how the contribution of the posterior corneal surface is considered in the calculation platform used for each IOL. In any case, these trends can vary among studies because of the specific characteristics of the sample analysed (magnitude and type of astigmatisms) or the method used for obtaining the subjective refraction. For example, Piovella et al. [11] obtained, by means of vector analysis, a mean ME of − 0.16 ± 0.48 D when analysing the efficacy of the astigmatic correction achieved with the AT LISA diffractive trifocal toric IOL. In contrast, Mojzis et al. [32] found the opposite trend with the same trifocal toric IOL, reporting a mean ME of 0.06 ± 0.30 D. In any case, in our series, the astigmatic correction achieved was satisfactory with both IOLs, which was also due to a good rotational behaviour of the IOL. Indeed, mean AE was 0.48 ± 3.21º and 0.38 ± 1.67º in the ATLISA and Synergy groups, respectively, which was associated with mean rotation levels of around ≤ 2º. These results are consistent with IOL rotation values reported by previous authors for some multifocal toric IOLs [10, 35, 36].

This study has several limitations that should be acknowledged. First, the number of cases per group is limited, with future studies with larger samples sizes being necessary to confirm our outcomes. Accordingly, it was not possible to perform sub-analysis as a function of axial length, differentiating the short and long eyes. Second, a hydrophilic IOL with a plate haptic design has been compared with an IOL of hydrophobic acrylic material and C-haptics with a different diameter and therefore differences between IOLs could not be only attributable to differences in the optical design of the IOL. However, the discrepancies in terms of material, lens diameter and design of the haptic could mainly have a role in the differential behaviour in terms of rotational stability and PCO incidence, and such differences have not been found in the current study. This suggests that the contribution of these potential differences is minimal and specially with low clinical relevance. Mihaltz et al. [37] conducted a prospective, randomised study to interocularly compare the visual performance after implantation of two different toric IOLs with different haptic designs: AT TORBI 709 M IOL from Carl Zeiss Meditec (plate haptic) and Tecnis toric IOL (C-haptic) from Johnson & Johnson. They found that both toric IOLs successfully reduced ocular astigmatism, with the Tecnis IOL showing better positional stability. In our series, differences did not reach statistical significance although fewer eyes implanted with the AT LISA IOL showed an IOL rotation within ± 5º (76.9%) compared to those implanted with the Synergy IOL (100.0%). Future studies with larger samples sizes must confirm the statistical significance of this trend. Finally, other aspects that could have influenced the outcomes have not been evaluated in the current study, such as capsular back size, time of rotation after surgery or postoperative course of the patients (hours after surgery resting in bed/going home, movements). This should be investigated further in future studies.

In conclusion, the two toric presbyopia-correcting IOLs evaluated provide an efficacious correction of pre-existing corneal astigmatism and visual rehabilitation across a great variety of distances. However, the visual performance achieved with the hybrid IOL combining the EDOF and diffractive multifocal pattern seems to be better for most visual demands, especially for distances closer than 40 cm. Furthermore, the near visual outcome is maintained with both toric presbyopia-correcting IOLs within functional levels under mesopic light conditions. It should be considered that this study compares very different IOLs in terms of material and geometry, not only in terms of optical design, and it is difficult to extract consistent conclusions about the exact cause for some of the differences detected. Future comparative studies with other types of multifocal toric IOLs as well as long-term studies should be conducted.