A comparison of clinical outcomes and optical performance between monofocal and new monofocal with enhanced intermediate function intraocular lenses: a case-control study

Background To compare clinical outcomes and optical performance of a new monofocal with enhanced intermediate function intraocular lenses (IOLs) with that of conventional monofocal IOLs. Methods Sixty eyes of 30 patients who underwent phacoemulsification with bilateral implantation of the ICB00 (15 patients) or ZCB00 (15 patients) IOLs were enrolled. Binocular corrected distance visual acuity (CDVA), distance corrected near visual acuity (DCNVA), and distance corrected intermediate visual acuity (DCIVA) were measured at 4 weeks after surgery. Patient satisfaction for overall, near, intermediate, and distance vision were assessed. The binocular defocus curves were measured. The root mean square of modulation transfer function (MTFRMS) was measured in the optical bench study. Results The mean binocular DCIVA was significantly better in the ICB00 group (0.01 logMAR) compared to the ZCB00 group (0.13 logMAR), but CDVA and DCNVA were not. The patient satisfaction for near and intermediate vision was significantly higher in the ICB00 group compared to the ZCB00. However, there was no difference in patient satisfaction for overall and distance vision between two groups. The defocus curves showed that mean visual acuity of the ICB00 group was significantly better than that of the ZCB00 group at between − 1.00 D to − 3.00 D of defocus. The ICB00 IOL had higher MTFRMS values at between − 0.50 D to − 2.00 D of defocus compared to the ZCB00 IOL. Conclusions The ICB00 IOL provides better binocular intermediate vision and higher satisfaction for near and intermediate vision than the ZCB00 IOL while maintaining excellent distance vision.

been developed to meet patients' need for near vision, but there is a limit to the increased incidence of subjective visual disturbance, including halos and glare [4][5][6].
Currently, extended computer use and younger age at cataract surgery also give rise to growing needs for intermediate vision [7][8][9]. The newly developed TECNIS Eyhance ICB00 (Johnson & Johnson Vision Care, Inc.), a monofocal with a higher-order aspheric anterior surface IOL to enhance intermediate function, sought to meet those needs while sparing distant vision and visual disturbance. It shares the same geometry with the conventional monofocal TECNIS 1-piece ZCB00 IOL (Johnson & Johnson Vision Care, Inc.) about 85% of the surface except for the modified aspherical anterior surface of the optics [10]. This unique anterior surface is intended to create a continuous power change from the periphery to the center inducing the continuous power profile created with a higher-order asphere and improves intermediate vision. It is based on the refractive technology, without diffractive rings or zones, and it is visually indistinguishable from the TENIS 1-piece ZCB00 IOL. Thus, we wanted to know how the visual performance improved as the anterior surface profile changed from the ZCB00 to ICB00.
The purpose of this study was to compare clinical outcomes in terms of distance, near, and intermediate visual acuities, visual disturbances, and spectacle independence between patients who underwent bilateral implantation of ZCB00 IOLs and patients who underwent bilateral implantation of ICB00 IOLs. Besides, we also evaluated the optical performance of two IOLs through optical bench testing.

Study population
This retrospective case-control study included patients who underwent cataract surgery with either the ZCB00 or ICB00 IOLs implanted bilaterally at the Korea University College of Medicine between March and October 2020. Patient who had a postoperative corrected distance visual acuity (CDVA) of 20/40 or better in the operated eye were included. Eyes with traumatic cataracts, a previous history of ocular surgery, eventful surgery (eg, anterior capsule tear), or postoperative complications were excluded. This study adhered to the tenets of the Declaration of Helsinki, and was approved by both the Institutional Review Board of Korea University Guro Hospital (IRB no. 2020GR0525) and that of Korea University Ansan Hospital (IRB no. 2020AS0344). The Institutional Review Board of Korea University Medicine waived the need for written informed consent from the participants, because of the study's retrospective design.

Patient examination
Preoperative uncorrected distance visual acuity (UDVA) was measured at 4 m. The preoperative corneal power, anterior chamber depth (ACD), and axial length (AL) were measured using an IOLMaster 500 (Carl Zeiss Meditec AG, Jena, Germany). The IOL power was calculated based on the predicted refraction by Haigis formula, and targeted between 0 and − 0.50 D. IOL constants of a0, a1, and a2 for the Haigis formula were − 1.302, 0.210, and 0.251, respectively.

Surgical technique
All phacoemulsification and IOL implantations were performed by one of two experienced surgeons (S.J.S. and E.Y.) in one of our two institutions under topical anesthesia with 0.5% proparacaine hydrochloride (Alcaine; Alcon Laboratories Inc., Fort Worth, Tx or Paracaine; Hanmi Pharm, Seoul, Korea). After making a 2.20-or 2.75-mm clear corneal incision, a 26-gauge needle and a capsulorrhexis forceps were used to create a continuous curvilinear capsulorrhexis slightly smaller than the IOL optic size. The phacoemulsification was performed with either the stop-and-chop or phaco-chop technique. The IOL was folded for implantation using an insertion system, and inserted into the capsular bag through a clear corneal incision. All patient was treated with topical 1.5% levofloxacin (Cravit; Santen Pharmaceutical, Osaka, Japan) and topical steroid eyedrop (1% prednisolone acetate (Pred Forte ® ; Allergan, Inc., Irvine, CA) or 0.1% fluorometholone (Santen Pharmaceutical)) 4 times daily, and 0.1% bromfenac sodium (Bronuck; Taejoon Pharm, Seoul, Korea) twice daily from 3 days before cataract surgery to 4 weeks after cataract surgery.

Patient evaluation
Postoperative monocular and binocular uncorrected and corrected distance visual acuity (CDVA) at 4 m, binocular uncorrected and distance corrected near visual acuity (UNVA, DCNVA) at 40 cm, and binocular uncorrected and distance corrected intermediate visual acuity (UIVA, DCIVA) at 66 cm were measured at postoperative visits 4 weeks after surgery. The distance corrected defocus curves were obtained binocularly at 4 m to measure the visual acuity with each defocus between − 3.00 D and + 1.00 D in 0.50 D intervals [6].
The refractive prediction error was defined as the difference between postoperative achieved refraction and preoperative targeted refraction (i.e., refractive prediction error = achieved spherical equivalent -targeted spherical equivalent). Mean absolute error (MAE) was defined as the mean absolute value of refractive prediction error and median absolute error (MedAE) was defined as the median absolute value of refractive prediction error [11].

Optical bench system
The optical bench system used in this study consisted of a LED light, the 1951 United States Air Force (1951 USAF) resolution test chart, an artificial pupil, a pupil camera, trial lens, model eye, and complementary metal-oxidesemiconductor (CMOS) camera (BFS-U3-120S4M-CS; FLIR Systems Inc., Wilsonville, OR) ( Fig. 1) [13]. The model eye composed of an aberration-free artificial cornea and a wet cell which was made of N-BK7 (DG100X100-600) and filled with a balanced salt solution, and they were mounted on the XYZ translation stage [14]. The IOL was fixed using an aspheric lens adapter which was mounted on the XYZ translation stage and then positioned in a wet cell. After that the lenses center and the camera were precisely aligned so that the image focus was on the camera's sensor. The 1951 USAF resolution chart was illuminated by 555 nm LED light, and the image formed by the model eye was obtained by the CMOS camera [14,15]. The trial lens was placed in front of the model eye to obtain defocus image between − 2.50 D and + 1.00 D in 0.50 D intervals [16]. These measurements were repeated at different pupil size from 2.0 mm to 5.0 mm in 1.0 mm increments using the artificial pupil with scale.
The images of the 1951 USAF target formed by two IOLs of 21.0 D ZCB00 and ICB00 IOLs were compared following International Organization for Standardization (ISO) 11,979-2 requirements and test methods (International Organization for Standardization, 2014. Ophthalmic Implants -Intraocular Lenses -Part 2: Optical Properties and Test Methods). The element 3 of the group 2 in the 1951 USAF resolution test chart was set to be 15 cycle per degree (CPD), which is approximately equivalent to 20/40 vision. The images were converted to through-focus modulation transfer function (MTF) in the horizontal and vertical directions using the MatLab (Mathworks, Inc., Natick, MA) [17]. The root mean square of the horizontal and vertical MTF (MTF RMS ) was calculated using the following formula [15]:

Statistical analysis
Data analysis was performed using the Statistical Package for the Social Sciences (version 20.0, SPSS, Inc.). Student's t tests, Mann-Whitney U tests, and Fisher's exact tests were performed to compare the clinical characteristics, IOLMaster 500 measurements, implanted IOL power, monocular UDVA, monocular and binocular CDVA, binocular CDVA, UNVA, DCNVA, UIVA, and DCIVA, incidence of photic phenomena, patient satisfaction score, and spectacle dependence score between the ZCB00 and ICB00 groups. A P value less than 0.05 was considered statistically significant. There was no significant difference in mean age, sex ratio, preoperative UDVA, or mean corneal power between the two groups. On the other hand, the ZCB00 group showed a shallower ACD, shorter AL, and higher IOL power compared to the ICB00 group (Table 2). Mean targeted and achieved refraction of the ICB00 group were − 0.23 ± 0.31 and − 0.16 ± 0.37 D, respectively, and those of the ZCB00 group were − 0.27 ± 0.19 and − 0.26 ± 0.34 D, respectively. There was no significant difference in MedAE and MAE between the ICB00 and ZCB00 groups (Table 3). Table 4 shows the comparison of postoperative visual acuity between the ICB00 and ZCB00 groups. The mean monocular UDVA and CDVA, and binocular CDVA at 4 m was 0.06, − 0.01, and − 0.04 logMAR for the ICB00 group, respectively, 0.07, − 0.02, and − 0.05 logMAR for the ZCB00 group, respectively, with no significant differences between the two groups. On the other hand, the mean binocular UNVA was significantly better in the ICB00 group (0.09 logMAR) compared to the ZCB00 group (0.35 logMAR) (p < 0.001). Besides, the binocular UIVA and DCIVA were also better in the ICB00    Figure 2 shows binocular distance-corrected defocus curves at 4 weeks after cataract surgery of the two groups. Both curves peaked at 0.00 D of defocus and decreased with increasing negative defocus. However, the ICB00 group achieved a smooth landing area with a less abrupt decrease in visual acuity, especially within the intermediate defocus range up to − 1.50 D. The mean visual acuity was 0.1 logMAR or more between + 1.00 D to − 1.50 D of defocus in the ICB00 group. The mean visual acuity of the ICB00 group was significantly better than that of the ZCB00 group at between − 1.00 D to − 3.00 D of defocus.

Clinical study
There was no significant difference in the incidence of glare, starburst, and halos between the ICB00 and ZCB00 groups ( Table 5). The mean patient satisfaction score for near and intermediate vision was significantly higher in the ICB00 group (4.0 ± 0.9 and 4.4 ± 0.6, respectively) than in the ZCB00 group (3.2 ± 0.9 and 3.7 ± 0.8, respectively) (P = 0.026 and P = 0.017, respectively; Fig. 3). However, there was no significant difference in the mean patient satisfaction score for overall and distance vision between the two groups. The spectacle dependence score for near and intermediate vision was significantly better in the ICB00 group (1.7 ± 1.3 and 1.1 ± 0.3, respectively) compared to the ZCB00 group (3.2 ± 1.4 and 2.3 ± 1.4, respectively), but not that for distance vision (Fig. 3).
Optical bench performance Figure 4 shows captured images of the 1951 USAF resolution test chart from two IOLs. For the ZCB00 IOL, as the minus diopters were added, the image was gradually blurred, and the image became indistinguishable from − 1.00 D. However, for the ICB00 IOL, the image was identifiable until − 2.00 D was added.
The highest MTF RMS values of the ICB00 IOL at − 0.50 D of defocus (0.690) was obtained in the pupil size of 2.0 mm (Fig. 5B and Table 6). On the other hand, the MTF RMS values of the ICB00 IOL at between − 1.00 D to

Discussion
This study showed that after the Eyhance ICB00 IOLs were implanted bilaterally, patients could obtain better intermediate and near vision than the ZCB00 IOL while maintained the distant vision. Moreover, there was no difference in the incidence of photic phenomena between the ICB00 and ZCB00 IOL. In the optical bench test, the Eyhance ICB00 IOL showed an excellent MTF curve at intermediate distances, and it was affected by the pupil size.
Although cataract surgery with monofocal IOL implantation is still the most common option, there is a gap between postoperative results and patient's expectations as it limits to improve only distant vision. At this point, many investigators have developed other IOL designs to improve near and intermediate vision, but those IOLs also have limitations as they accompany unwilling phenomena such as reduced contrast sensitivity, halos, and glares [18][19][20]. Besides, as the optical technologies differ, the subjects to apply those advanced IOLs are limited. Therefore, the Eyhance ICB00 IOL could be a good option as it shares the same geometry with the monofocal 1-piece IOL and provides an improved intermediate and near vision, and better spectacle independence as well, without accompanying other unwilling phenomena.
Previous studies reported the Eyhance ICB00 IOL's effectiveness as it provided improved intermediate vision compared to the monofocal 1-piece IOL [10,21,22]. In those previous studies, the Eyhance ICB00 IOL yielded better UIVA, higher spectacle independence at a b Fig. 3 [24]. Previous study showed that the through-focus MTF curve of the ICB00 shifted to a myopic defocus of − 0.50 D at a 2.0 mm pupil size and the maximum MTF value was obtained at − 0.5 D defocus [25]. However, in this study, the maximum MTF value was obtained at 0.0 D defocus without myopic shift of the MTF curve at a 2.0 mm pupil size. Considering the myopic shift of the through-focus MTF curve in the previous study, it is thought that a relatively lower MTF value (0.459) was measured at − 0.5 D defocus without myopic shift of the MTF curve in this study.
One limitation of the current study is that the sample size was relatively small, the follow-up period was relatively short, and the study design retrospectively reviewed the medical records. The other is that we did not evaluate whether patients' pupil size had impacts on visual acuity.

Conclusions
In conclusion, the TECNIS Eyhance ICB00 IOL may be a good option for both clinicians and patients. It provided better intermediate and near vision than the TECNIS 1-piece IOL while maintaining excellent distance vision without worsening the visual symptoms. Moreover, the results of the optical bench test, which showed that the Eyhance ICB00 IOL had higher MTF values between − 0.50 D and − 2.00 D of defocus compared to the ZCB00 IOL, supported these clinical outcomes.