In this study, we conducted a comprehensive clinical comparison of the visual performance of the TECNIS ZMB00 IOL and the Lentis Comfort LS-313 MF15 IOL in a large sample from a single eye institute. Although very high corrected visual acuity was maintained at all distances in both groups, corrected distance visual acuity was better in the ZMB00 group than in the LS-313 MF15 group (Table 2). Regarding uncorrected visual acuity, although uncorrected distance visual acuity (UDVA) was high in both IOL groups, the ZMB00 IOL group had significantly better uncorrected near visual acuity (UNVA) (Table 2 and Fig. 1) and UDVA (Table 2). On the other hand, UIVA was 0.20 logMAR in the ZMB00 group and 0.27 logMAR in the LS-313 MF15 group (Supplementary Table S2B), with no significant difference between the two groups. Oshika et al.17 showed that, over a 1-year study period, the Lentis Comfort LS-313 MF15 provided good distance and intermediate vision (approximately 0.0 logMAR UDVA and approximately 0.1 logMAR uncorrected intermediate visual acuity (UIVA) at 70 cm), whereas near visual acuity remained unsatisfactory (approximately 0.5 logMAR UNVA at 30 cm). The slightly worse UIVA of the LS-313 MF15 group in our study might be partly because intermediate VA was measured at 50 cm in this study. Because the Lentis Comfort LS-313 MF15 has + 1.5 D (+ 1.06 D on the corneal plane; 94 cm) of near addition power and ZMB00 has + 4.00 D (+ 3.2 D on the corneal plane; 31 cm) of near addition16–21, intermediate VA could be slightly worse at 50 cm than at 60–70 cm in the LS-313 MF15 group. This might also contribute to the lack of any significant difference between the UIVAs of the two groups. The distance at which intermediate visual acuity should be measured is a source of controversy, with opinions ranging from 50 cm to 100 cm22. The handheld devices and computers used in daily life commonly require users to rely on intermediate vision23. Within arm’s reach is also a practical distance for testing intermediate vision, with patients holding a test chart. By this standard, intermediate vision should be measured at a smaller distance in Japanese patients than in American or European patients due to differences between the populations in average body size and arm length. Therefore, we measured intermediate visual acuity at 50 cm, which was within the reach of most Japanese patients in this study.
We measured contrast sensitivity using the CGT-1000 instrument. This device can automatically measure contrast sensitivity20 at six sizes and 13 contrast levels with or without glare. In this study, the contrast sensitivity of the Lentis Comfort LS-313 MF15 group as measured with this device was significantly better than that of the ZMB00 group both with and without glare (Table 2, Figs. 1 and 2). Oshika et al.17 showed that the contrast sensitivity function of the Lentis Comfort LS-313 MF15 IOL group resembled that of an age-matched normal control sample over a 12-month study period after cataract surgery. Song et al.21 reported that the Lentis Comfort had a contrast sensitivity similar to those of monofocal IOLs and extended-range-of-vision IOLs (the Tecnis Symfony ZXR00). With the Tecnis Symphony ZXR00, the range of vision can be extended by elongating the focus based on an achromatic diffractive echelette design with nine diffractive rings, and this IOL was reported to have similar contrast sensitivity to monofocal IOLs24. On the other hand, we previously reported that the contrast sensitivity measured with the CGT-1000 was better in the monofocal group (ZCB00 IOL) than the multifocal group (ZMB00 IOL) at most frequencies both with and without glare16. In this study, the Lentis Comfort LS-313 MF15 IOL group had significantly better contrast sensitivity than the TECNIS ZMB00 IOL group with and without glare, which is consistent with the results of previous studies as a whole. Diffractive multifocal IOLs such as the TECNIS ZMB00 divide light into two foci; in general, TECNIS multifocal IOLs use 41% of incoming light for distance vision and 41% for near vision, regardless of the pupil diameter, while the remaining 18% is lost to higher-order scattering25. Recent research has confirmed that the use of 41% of light for distance vision allows photopic, high-contrast distance acuity comparable to that provided by monofocal IOLs26–29. The TECNIS ZMB00 IOL is a second-generation multifocal IOL with an aspherical design developed to improve contrast sensitivity by reducing or cancelling the normal positive spherical aberration of the cornea; the performance of this IOL has relatively little dependence on pupil size. Compared to spherical IOLs, aspherical IOLs reportedly show decreased wavefront spherical aberrations and improved contrast sensitivity30–35. Aspherical multifocal IOLs thus reduce the incidence and severity of halos and glare (i.e., steps at the edges of different ring zones), issues that are inherent to diffractive multifocal IOL designs and observed more often with spherical multifocal IOLs. In fact, rather than deterioration of contrast sensitivity with the use of diffractive multifocal IOLs, we have reported better contrast sensitivity both with and without glare in the multifocal group than in normal 60-year-old Japanese subjects assessed by Takahashi16,20,36. The Lentis Comfort LS-313 MF15, on the other hand, is a rotationally asymmetric, refractive IOL that combines a distance vision zone with a sector-shaped near vision zone featuring + 1.50 D power addition in the IOL plane (+ 1.06 D in the corneal plane)17,21, with a smooth transition between the two optical zones that divide light into two foci with an extended focus effect. Mild power addition with a smooth transition area between the two different optical zones helps suppress light scattering and undesirable phenomena. According to the manufacturer’s calculation, the Lentis Comfort has an optical loss of 5%, resulting in good postoperative contrast sensitivity, which is further enhanced by its hydrophilic structure. Previously, reports of calcification and opacification contributed to hydrophilic acrylic IOLs being less widely used than hydrophobic acrylic IOLs37. However, the latest generation of hydrophilic acrylic IOLs, such as the Lentis Comfort, avoid these problems; additional proposed advantages include reduced dysphotopsia, excellent biocompatibility, improved optical clarity, robustness, and protection against biocontamination38.
Higher-order aberrations (ocular/internal, scaled to a pupil size of 4 mm) (WF_4_post_O_TotalHOA/Third/Fourth/Trefoil/Coma/Tetrafoil/Spherical, WF_4_post_I_Astigmatism/TotalHOA/Third/Trefoil/Coma/Tetrafoil/Spherical) were significantly smaller in the ZMB00 IOL group (Table 2 and Fig. 1), and higher-order aberrations (ocular/internal, scaled to a pupil size of 4 mm) (WF_4_post_O_2ndAstig, WF_6_post_O_TotalHOA/Third/Fourth/Trefoil/Spherical, WF_6_post_I_Astigmatism/TotalHOA/Third/Fourth/Trefoil/Spherical) were less marked in the ZMB00 IOL group (Table 2). This might be partly because the anterior surface of the ZMB00 has negative spherical aberration (-0.27 µm) as compensation for the positive spherical aberration of the cornea, whereas the Lentis Comfort IOL has an aspheric, aberration-free (0.0 µm) distance vision zone with a sector-shaped near vision zone17,21. Although aberrations can help improve the depth of focus, they can have a negative influence on contrast sensitivity39,40.
A heatmap of correlation coefficients revealed significant positive correlations between contrast sensitivity with/without glare (logarithm) and uncorrected/corrected distance visual acuity (logarithm) in the ZMB IOL group (Fig. 4). This implies that contrast sensitivity with/without glare may be critical for uncorrected/corrected distance visual acuity in this group. Additionally, significant positive correlations were observed between the higher-order aberrations (internal, scaled to a pupil size of 4 mm) and contrast sensitivity (logarithm) (Fig. 4); in other words, the higher-order aberrations had significantly negative correlations with contrast sensitivity. By contrast, the heatmap of correlation coefficients revealed significant positive correlations between contrast sensitivity with/without glare (logarithm) and higher-order aberrations (ocular/internal, scaled to a pupil size of 4 mm/6 mm) in the Lentis Comfort LS-313 MF15 IOL group (Fig. 5); in other words, contrast sensitivity correlated negatively with higher-order aberrations. Nochez et al.39 reported a significant negative correlation between total ocular spherical aberration and contrast sensitivity, and Piers et al.40 showed that contrast sensitivity was best when spherical aberration was completely corrected. The negative correlation observed between the higher-order aberrations and contrast sensitivity in both groups in our study appears consistent with previous reports.
In our study, approximately 82.2% of patients in the ZMB00 group were fully spectacle-independent after IOL implantation. This result is consistent with previous reports on ZMB00, in which 82.6–92.8% of patients achieved complete spectacle independence14,26,41,42. In contrast, the frequency of spectacle independence in our LS-313 MF15 group was approximately 39.5%. Distance/near spectacle independence was significantly higher in the ZMB00 group (Table 2 and Fig. 1). Multifocal glasses are widely used by Japanese people with presbyopia; patients who need spectacles for near vision often use multifocal glasses that correct distance vision as well. This may be a reason for the superior rate of distance spectacle dependence in the Lentis Comfort group, whose UDVA was as satisfactory as that of the ZMB00 group.
The NEI VFQ-25 is a self-report questionnaire used to measure vision-related health status43,44. This questionnaire can be used to evaluate changes in subjective visual function following cataract surgery, and it has been translated into several languages, including Japanese; the Japanese version was validated by Suzukamo et al.45 In our study, VFQ-25 scores for Driving_General/Nighttime were likely better in the LS-313 MF15 IOL group (Table 2 and Fig. 3). Difficulty in driving at night has been linked to perception of optical phenomena such as glare and halos46. Song et al.21 reported a significantly lower incidence of halos in the LS-313 MF15 group than in the Tecnis Symphony ZXR00 group, and visual quality scores at night were significantly better in the former group than in the monofocal group (implanted with the L-313, a lens made on the same platform as the LS-313 MF15). Yoo et al.47 reported that the Lentis Comfort LS-313 MF15 was associated with significantly lower rates of glare and halos than the same IOL with a basic design providing + 3 D near addition (Lentis M plus LS-313 MF30). Oshika et al.17 reported that the defocus curve of the Lentis Comfort presented a gradual decrease from distance vision to near vision, in contrast to the 2-peak curve seen with traditional bifocal IOLs. The low-addition design of the Lentis Comfort made it possible to have an elongated focal area and to minimize unfocused images that would generate halos. In this way, the incidence of undesirable photic phenomena might be reduced, which, in turn, might contribute to the high score for nighttime driving. Thus, our finding that the Lentis Comfort was associated with better nighttime driving scores than the ZMB00 appears to be consistent with prior studies.
One limitation of this study is that intermediate visual acuity was measured only at 50 cm and near visual acuity at 30 cm. In Japanese patients, visual acuity at these distances is essential for working at arm’s length and for reading. Ideally, however, visual acuity should be measured at a wider range of distances to gauge the performance of the lenses in detail. As mentioned above, evidence suggests that intermediate visual acuity should be measured at distances between 50 cm and 100 cm22. Distances within arm’s reach are practical for intermediate vision tests, for example, when the patient holds a test chart. As Japanese people are relatively short in average height and arm length, we measured intermediate visual acuity at 50 cm, assumed to be within the reach of most patients in the study.
A second limitation concerns the retrospective nature of the study; it is conceivable that the two patient groups had different social backgrounds. However, this large-scale single-center study followed a consistent protocol: after written informed consent was obtained from all the patients before surgery, we conducted the same series of pre- and postoperative examinations, including the VFQ-25, which captures information about the social background of the patients. We evaluated parameters 10 weeks after the last surgery in cataract patients who underwent bilateral ZMB00 or LS-313 MF15 implantation, with the right and left lenses implanted within 3 months of each other, and strictly adjusted for the variables of age, sex, axial length, subjective refraction SE, subjective refraction CYL, corneal astigmatism (keratometric cylinder), and corneal higher-order aberrations. The data contain a mixture of items evaluated in both eyes together or in each eye separately. Our analysis accounted for any bias, as we used a linear mixed model and corrected for multiple observations for each eye per case. Although this study is retrospective, each patient receiving lenses was randomly and independently sampled, and all endpoints were measured. In statistical analysis, random assignment is widely assumed not to bias the outcomes of the analysis, even if the numbers of cases differ. An example of this is 1:n allocation in clinical trials.
In conclusion, we compared the visual performance of the TECNIS ZMB00 IOL and the Lentis Comfort LS-313 MF15 IOL. Patients in the ZMB00 group had better UNVA, smaller higher-order aberrations (ocular/internal, scaled to a pupil size of 4 mm) (WF_4_post_O_TotalHOA/Third/Fourth/Trefoil/Coma/Tetrafoil/Spherical, WF_4_post_I_Astigmatism/TotalHOA/Third/Trefoil/Coma/Tetrafoil/Spherical), and higher distance/near spectacle independence, whereas patients in the Lentis Comfort group had better contrast sensitivity (6.3/4.0/2.5/1.6/1.0/0.7 degrees) and contrast sensitivity with glare (4.0/2.5/1.6/1.0/0.7 degrees). At a high performance level, the two IOL groups showed different characteristics with regard to various visual parameters.