Journal of Refractive Surgery

Original Article Supplemental Data

Individually Customized IOL Versus Standard Spherical Aberration-Correcting IOL

Jens Schrecker, MD; Simon Schröder, PhD; Achim Langenbucher, PhD; Berthold Seitz, MD; Timo Eppig, PhD

Abstract

PURPOSE:

To compare the visual performance of an individually customized intraocular lens (IOL) versus a standard spherical aberration-correcting IOL.

METHODS:

In this prospective comparative study, 74 eyes of 60 patients scheduled for cataract surgery were randomized in a 2:1 ratio to receive either an individually customized IOL (; HumanOptics AG, Erlangen, Germany; customized group) or an aspheric IOL with a standard correction of spherical aberration (SA) (Tecnis ZCB00; Johnson & Johnson Vision Surgical, Inc., Santa Ana, CA; standardized group). In the customized group, IOL calculation was based on a minimum of a merit function that contained terms representing residual refraction, residual SA, and modulation transfer function. In the standardized group, the IOL was calculated with a routine procedure using the Holladay formula and had a standard SA correction of −0.27 µm. Refraction, visual acuity (far, intermediate, near), photopic and mesopic contrast sensitivity, defocus curve, corneal and ocular spherical aberration, and pupil size were measured 4 weeks and 3 months postoperatively.

RESULTS:

The customized group comprised 48 eyes of 37 patients and the standardized group 26 eyes of 23 patients. At 3 months, mean total ocular SA (5 mm) was 0.04 ± 0.06 µm in the customized group and −0.01 ± 0.05 µm in the standardized group. Uncorrected distance visual acuity and distance-corrected near visual acuity were statistically significantly better in the customized group. Contrast sensitivity testing yielded significantly better results in the customized group under photopic and mesopic conditions for almost all spatial frequencies. Compared to the standardized group, the defocus curve of the customized group showed a wider plateau surrounding the distance focal point.

CONCLUSIONS:

With the implantation of an individually optimized aspheric IOL visual performance, especially contrast sensitivity, can be significantly improved compared to a standard aberration-correcting IOL.

[J Refract Surg. 2019;35(9):565–574.]

Abstract

PURPOSE:

To compare the visual performance of an individually customized intraocular lens (IOL) versus a standard spherical aberration-correcting IOL.

METHODS:

In this prospective comparative study, 74 eyes of 60 patients scheduled for cataract surgery were randomized in a 2:1 ratio to receive either an individually customized IOL (; HumanOptics AG, Erlangen, Germany; customized group) or an aspheric IOL with a standard correction of spherical aberration (SA) (Tecnis ZCB00; Johnson & Johnson Vision Surgical, Inc., Santa Ana, CA; standardized group). In the customized group, IOL calculation was based on a minimum of a merit function that contained terms representing residual refraction, residual SA, and modulation transfer function. In the standardized group, the IOL was calculated with a routine procedure using the Holladay formula and had a standard SA correction of −0.27 µm. Refraction, visual acuity (far, intermediate, near), photopic and mesopic contrast sensitivity, defocus curve, corneal and ocular spherical aberration, and pupil size were measured 4 weeks and 3 months postoperatively.

RESULTS:

The customized group comprised 48 eyes of 37 patients and the standardized group 26 eyes of 23 patients. At 3 months, mean total ocular SA (5 mm) was 0.04 ± 0.06 µm in the customized group and −0.01 ± 0.05 µm in the standardized group. Uncorrected distance visual acuity and distance-corrected near visual acuity were statistically significantly better in the customized group. Contrast sensitivity testing yielded significantly better results in the customized group under photopic and mesopic conditions for almost all spatial frequencies. Compared to the standardized group, the defocus curve of the customized group showed a wider plateau surrounding the distance focal point.

CONCLUSIONS:

With the implantation of an individually optimized aspheric IOL visual performance, especially contrast sensitivity, can be significantly improved compared to a standard aberration-correcting IOL.

[J Refract Surg. 2019;35(9):565–574.]

Wavefront analysis of the eye has widely expanded our knowledge of the complex refractive errors of this high-performance organ. The use of Zernike polynomials is the prevailing method to characterize these refractive deficiencies. The spherical aberration (SA) Z40 has the largest impact of the higher order aberrations (HOAs) on visual performance as shown by theoretical studies based on pseudophakic eye models1,2 and studies using adaptive optics vision simulators.3,4 With aberration-correcting IOLs, a significant improvement of contrast sensitivity and visual acuity and a decrease of photopic phenomena is possible.5–11 Spherical IOLs typically add a significant portion of positive SA to the eye's aberrations, whereas aspheric lenses can be tailored to a specific amount of SA or zero SA. Therefore, conventional spherical lenses are more frequently replaced by aspheric IOLs to either compensate just for the intrinsic SA of the IOL12 (zero SA) or counterbalance the SA of the cornea by a fixed amount.13 In some cases, especially with negative corneal SA such as after refractive surgery for hyperopia, spherical lenses may represent the better solution. Moreover, the absolute target of zero residual SA may not be the optimum for best visual outcomes despite being the optimum from a purely optical point of view. Some studies report optimum image quality with zero SA,3 whereas others state that a residual SA of up to +0.1 µm may be the best possible compromise between depth of focus and contrast sensitivity.14,15 With all of these facts in mind, an individually tailored optic design based on the actual corneal SA should achieve the best results.16–18

To date, ophthalmologists have limited choices regarding the level of SA correction with an IOL. The most widespread option is the Tecnis ZCB00 IOL (Johnson & Johnson Vision Surgical, Inc., Santa Ana, CA), providing 0.27 µm of negative SA to the optical system. This value is based on clinical studies showing an average SA of the cornea of +0.27 µm.13 However, regarding the individual corneal SA, there is a large variability within the population.19,20 Consequently, depending on the individual corneal SA, a variable amount of residual ocular SA remains after standard aberration-correcting IOL implantation. Thus, the targeted residual SA will only be achieved in a certain percentage of eyes.

The Invidua-aA IOL (HumanOptics AG, Erlangen, Germany) is a novel individually customized aspheric lens designed to compensate for an individual amount of corneal SA. In our recently published study,21 we showed that the implantation of this IOL was effective in reducing the overall ocular SA. The aim of the current study was to compare the visual performance of an individually optimized IOL with an established standard aberration-correcting IOL.

Patients and Methods

This prospective comparative study was performed at the Rudolf Virchow Klinikum Glauchau, Germany. Patients with age-related cataract, an expected postoperative visual acuity of 20/25 or better, and a corneal astigmatism of less than 1.00 diopters (D) were enrolled. Exclusion criteria were diseases that might impair vision, comorbidities that could reduce in-the-bag stability of the IOL, and previous ocular surgery or trauma. All patients provided written informed consent before enrollment. The study was approved by the local ethics committee and followed the tenets of the Declaration of Helsinki.

IOLs and Calculation

Patients in the customized group were implanted with the individually customized IOL (Invidua-aA), a one-piece hydrophilic acrylic (n = 1.46) lens with an optic diameter of 6 mm and an overall length of 12.5 mm. The lens is based on the design of a zero SA standard IOL (Aspira-aA; HumanOptics AG) with the anterior optic surface being a rotationally symmetric individually customized asphere. Patients in the standardized group were implanted with the aspheric IOL Tecnis ZCB00 (Johnson & Johnson Vision Surgical, Inc.). This one-piece IOL has a 6-mm biconvex optic, an overall diameter of 13 mm, and a standard correcting SA value of −0.27 µm at a pupil size of 6 mm.

IOL power calculation for both study lenses was based on optical biometry (IOLMaster 500; Carl Zeiss Meditec AG, Jena, Germany) with the aim of postoperative emmetropia to minimal myopia. Tecnis lenses were calculated with regard to our standard procedure using the Holladay 1 formula.

The calculation of the customized lens was done in a computer study by means of numerical ray tracing. Of a set of three tomographic measurements (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany), the corneal data for IOL calculation were determined by the manufacturer and imported as best-fit sphere plus the full spectrum of corneal HOAs as proposed by Koch and Wang.17 With the help of a custom written software, individual eye models were constructed with an optical design software (OpticStudio; Zemax, LLC, Kirkland, WA).

In the first step, an optical design of a standard zero SA hydrophilic IOL (Aspira-aA) was placed in the eye model using the Haigis formula with optimized constants-triplet for defining the effective lens position and optimum IOL power. Subsequently, the anterior surface of the IOL was altered to find a minimum of a function with terms representing residual refraction, residual SA, image quality in terms of modulation transfer function, and manufacturing constraints on the lens' geometry. Additionally, a certain degree of robustness was considered to make the IOL more tolerant to potential decentration of up to 0.3 mm.22

Clinical Examination

All patients enrolled had a comprehensive ophthalmologic examination, including slit-lamp biomicroscopy and macular OCT, optical biometry (IOLMaster 500), and corneal tomography (Pentacam HR).

Four weeks and 3 months postoperatively, follow-up examinations included subjective refraction, uncorrected (UDVA) and corrected (CDVA) distance visual acuity, uncorrected (UIVA) and distance-corrected (DCIVA) intermediate visual acuity, uncorrected (UNVA) and distance-corrected (DCNVA) near visual acuity, slit-lamp examination, corneal tomography (Pentacam HR), wavefront measurement including total ocular SA Z40 (iTrace; Tracey Technologies, Houston, TX), defocus curve, contrast sensitivity (Functional Vision Analyzer; Stereo Optical Co., Inc., Chicago, IL), and pupil diameter (PupilX; Albomed GmbH, Schwarzenbruck, Germany). Investigator and patients were masked with respect to the study group.

All tests of visual performance were performed monocularly. Distance visual acuity was evaluated at 5 m with numerical optotypes (sizes according to EN ISO 8596). Intermediate (1 and 0.63 m) and near (0.4 m) vision was measured using the appropriate Early Treatment Diabetic Retinopathy Study (ETDRS) charts (Precision Vision, Woodstock, IL). Regarding defocus curve, distance-corrected visual acuity was measured at 5 m through different levels of defocus induced with trial lenses between 2.00 and −3.00 D in steps of 0.50 D. Photopic (85 cd/m2) and mesopic (3 cd/m2) contrast sensitivity was determined with and without glare and pupil diameter was measured under photopic, mesopic, and scotopic conditions.

Statistical Analysis

The SPSS for Windows software package (version 22; IBM Corporation, Armonk, NY) was used for statistical analyses. Log values were used for contrast sensitivity outcomes and logMAR notation for visual acuity. We performed non-parametric analyses with the Wilcoxon ranked-sum test for comparisons between preoperative and postoperative data for each eye. To compare the two independent groups, the Mann–Whitney U test was applied. The chi-square test was used for comparing percentages of categorical data between the IOL model groups. A P value of less than .05 was considered statistically significant. The primary endpoint of this comparative study was contrast sensitivity. Secondary endpoints were visual acuity for far, intermediate, and near distance. For calculation of the power, we assumed an alpha error (type 1 error) of 5%. With an intended randomization of 2:1, post-hoc power analysis shows a type 2 error of 90% (for non-parametric testing and an effect size of 0.7).

Results

Preoperative clinical data for both groups are shown in Table 1. No significant differences were found regarding axial length, anterior chamber depth, corneal astigmatism, and corneal SA Z40. Patients in the customized group were slightly younger (mean: 68.9 vs 72.4 years). All patients completed the 4-week and 3-month follow-up examinations. For a pupil diameter of 4.5 mm, the SA correction values of the implanted individually customized IOLs ranged from −0.57 to 0.23 µm (median: 0.01 µm).

Preoperative Patient Demographics and Clinical Information

Table 1:

Preoperative Patient Demographics and Clinical Information

Visual and Refractive Outcomes

Table 2 summarizes visual and refractive outcomes of the study groups 3 months after surgery. At this follow-up, UDVA and DCNVA were significantly better in the customized group (P = .046 and .009, respectively). The customized group likewise performed slightly better in UNVA and DCIVA at 0.63 m but without statistically significant differences. The visual acuity results of the other tested distances also showed no significant differences between the groups. Four-week outcomes are listed in Table A (available in the online version of this article). Figure 1 displays the cumulative monocular CDVA, DCIVA, and DCNVA for both groups at 3 months.

3-Month Postoperative Monocular Visual Acuity and Refraction

Table 2:

3-Month Postoperative Monocular Visual Acuity and Refraction

4-Week Postoperative Monocular Visual Acuity and Refraction

Table A:

4-Week Postoperative Monocular Visual Acuity and Refraction

Cumulative monocular Snellen uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), distance-corrected intermediate visual acuity (DCIVA), and distance-corrected near visual acuity (DCNVA) (20/x or better) in the customized group and standardized group 3 months after surgery.

Figure 1.

Cumulative monocular Snellen uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), distance-corrected intermediate visual acuity (DCIVA), and distance-corrected near visual acuity (DCNVA) (20/x or better) in the customized group and standardized group 3 months after surgery.

We found a significant difference in the postoperative spherical equivalent at 3 months (P = .007), which was slightly shifted toward hyperopia in the customized group (mean: 0.13 ± 0.42 D) and toward myopia in the standardized group (mean: −0.13 ± 0.39 D) (Table 2, Figure 2). In total, 95.8% of the eyes in the customized group and 96.2% of eyes in the standardized group were within ±1.00 D and 68.8% of eyes in the customized group and 84.6% of eyes in the standardized group were within ±0.50 D of the targeted spherical equivalent. After 3 months, the refractive cylinder was 0.50 D or less in 93.8% of eyes in the customized group and 92.2% of the eyes in the standardized group (Figure 3).

Distribution of spherical equivalent (diopters [D]) at 3 months postoperatively.

Figure 2.

Distribution of spherical equivalent (diopters [D]) at 3 months postoperatively.

Refractive cylinder 3 months postoperatively. D = diopters

Figure 3.

Refractive cylinder 3 months postoperatively. D = diopters

As displayed in Figure 4, the defocus curve of the customized group showed a wider area on both sides and a wider plateau surrounding the distance focal point with a median visual acuity of 0.0 logMAR between +0.50 and −0.50 D. The differences between the groups in favor of the customized group were statistically significant for six defocus levels (from +2.00 to +0.50 D and −2.00 and −3.00 D).

Monocular distance-corrected defocus curves (median, range) 3 months after surgery. D = diopters * = statistically significant difference between the groups

Figure 4.

Monocular distance-corrected defocus curves (median, range) 3 months after surgery. D = diopters * = statistically significant difference between the groups

Preoperative and Postoperative Spherical Aberration

Preoperatively, there was no statistically significant difference in the corneal SA Z40 (total of anterior and posterior corneal surfaces) between the customized group and the standardized group for a 5-mm (P = .132) measuring zone (Table 1). The median corneal SA of all included eyes (n = 74) was 0.317 µm with a range of 0.11 to 0.50 µm.

At 3 months postoperatively, the corneal SA remained stable in both groups (customized group: preoperative: 0.31 ± 0.10 µm, after 3 months: 0.29 ± 0.12 µm; P = .061) (standardized group: preoperative: 0.34 ± 0.09 µm, after 3 months: 0.33 ± 0.08 µm; P = .167). The corneal SA showed no statistically significant differences between groups for the 5-mm zone (P = .069; Table 3).

3-Month Postoperative Corneal and Ocular Spherical Aberration (µm)

Table 3:

3-Month Postoperative Corneal and Ocular Spherical Aberration (µm)

Mean total ocular SA (5 mm) at 3 months was 0.04 ± 0.06 µm in the customized group. In the standardized group, a slight overcorrection was observed with a mean total ocular SA of −0.01 ± 0.05 µm (Table 3). Overall, there was a statistically significant difference between both groups (P < .001) (Table 3). Figure 5 shows the preoperative corneal SA Z40 compared to the postoperative total ocular SA Z40 for a diameter of 5 mm for both groups. Table B (available in the online version of this article) lists outcomes at 4 weeks and with a 6-mm pupil.

Corneal (preoperative) and ocular (postoperative) spherical aberration coefficient Z40 for a 5-mm diameter. The upper and lower margins of the box plot correspond to the 25th and 75th percentiles, respectively. The whiskers mark the 5th and 95th percentiles. C-Group = customized group; S-Group = standardized group

Figure 5.

Corneal (preoperative) and ocular (postoperative) spherical aberration coefficient Z40 for a 5-mm diameter. The upper and lower margins of the box plot correspond to the 25th and 75th percentiles, respectively. The whiskers mark the 5th and 95th percentiles. C-Group = customized group; S-Group = standardized group

Postoperative Corneal and Ocular Spherical Aberration (µm)

Table B:

Postoperative Corneal and Ocular Spherical Aberration (µm)

Pupil Size

At 3 months postoperatively, the mean photopic, mesopic, and scotopic pupil diameters in the customized group were 3.29 ± 0.47 mm (range: 2.60 to 4.60 mm), 4.07 ± 0.55 mm (range: 3.10 to 5.80 mm), and 4.77 ± 0.65 mm (range: 3.20 to 6.20 mm), respectively. The mean pupil diameters in the standardized group were slightly higher: 3.73 ± 0.59 mm (range: 2.50 to 5.00 mm) for photopic, 4.56 ± 0.77 mm (range: 2.90 to 5.90 mm) for mesopic, and 5.17 ± 0.81 mm (range: 3.20 to 6.40 mm) for scotopic.

Contrast Sensitivity Outcomes

Contrast sensitivity outcomes 3 months after surgery are summarized in Figure 6. Differences between groups at photopic and mesopic conditions were statistically significant in favor of the customized group at almost all spatial frequencies, with and without glare. The only exception was at 18 cpd under mesopic conditions.

(A–B) Photopic and (C–D) mesopic contrast sensitivity (median, range) measured with and without glare source 3 months after surgery. cpd = cycles per degree * = statistically significant difference between the groups

Figure 6.

(A–B) Photopic and (C–D) mesopic contrast sensitivity (median, range) measured with and without glare source 3 months after surgery. cpd = cycles per degree * = statistically significant difference between the groups

Subgroup Analysis

According to the SA-correcting effect of the Tecnis IOL, we performed a subgroup analysis and included in the standardized group only eyes with a preoperative corneal SA (6-mm zone) of 0.27 ± 0.10 µm. Additionally, we excluded statistical outliers of pupil diameter in both groups at the 3-month visit and of preoperative corneal SA in the customized group. With these criteria, we obtained a new case number of 35 eyes in the customized subgroup and 12 eyes in the standardized subgroup. The subgroup analysis showed no statistically significant difference in the preoperative corneal SA (6 mm) between subgroups (P = .778), but the SA values were still slightly higher (although with a smaller range), with a mean corneal SA of 0.30 ± 0.11 µm (range: 0.11 to 0.50 µm) in the customized subgroup and 0.28 ± 0.06 µm (range: 0.19 to 0.36 µm) in the standardized subgroup. In photic pupil diameter, there was likewise no statistically significant difference between both subgroups (P = .064), with a mean photopic pupil diameter of 3.29 ± 0.47 mm (range: 2.60 to 4.60 mm) in the customized subgroup and 3.53 ± 0.35 mm (range: 3.00 to 4.00 mm) in the standardized subgroup.

The results of the subgroup analyses supported the results of the primary group comparison. At the 3-month visit, mean CDVA was −0.02 ± 0.04 logMAR (median: 0.00 logMAR; range: −0.10 to 0.00 logMAR) in the customized subgroup and −0.01 ± 0.05 logMAR (median: 0.00 logMAR; range: −0.10 to 0.10 logMAR) in the standardized subgroup. Mean DCNVA was 0.37 ± 0.14 logMAR (median: 0.40 logMAR; range: −0.10 to 0.60 logMAR) in the customized subgroup and 0.49 ± 0.13 logMAR (median: 0.49 logMAR; range: 0.30 to 0.70 logMAR) in the standardized subgroup. The difference in DCNVA was statistically significant (P = .013). Defocus curves showed better visual acuity in the customized subgroup over the entire range from +2.00 to −3.00 D and differences were statistically significant at defocus levels of +0.50 D (P = .025), −0.50 D (P = .025), −1.50 D (P = .042), −2.00 D (P = .006), and −3.00 D (P = .005). In contrast sensitivity testing, the customized subgroup showed significantly better results across almost all lighting conditions and spatial frequencies (except for 12 and 18 cpd).

Complications

There were no intraoperative complications in both groups. No IOL decentration or tilt was observed after 4 weeks. At the 3-month examination, 1 eye of the standardized group showed a slightly tilted IOL. Nd:YAG capsulotomy was performed in 2 eyes (4.2%) in the customized group and in 1 eye (3.8%) in the standardized group before the 3-month visit.

Discussion

Currently, a few aspheric IOLs are available for clinical application, with asphericity levels varying significantly between models. A frequently implanted aberration-correcting IOL is the Tecnis ZCB00, which provides 0.27 µm of negative SA to the optical system with the aim of adjusting the postoperative ocular SA to zero. Several studies demonstrated that this IOL can reduce the total ocular SA and improve the postoperative visual performance compared to spherical and aspheric aberration-free IOLs.23,24 It was also reported that implantation of Tecnis ZCB00 IOLs results in normal straylight25 and allows for an optimized optical quality and a high level of patient satisfaction.26 Other studies showed that a custom selection of IOLs considering the HOA and especially the SA of the cornea may yield improved visual results compared to a random choice of different aspheric lens types.16–18 However, SA-correcting IOLs available today can only compensate for a fixed amount of spherical aberration and the variation of SA in human corneas is fairly large.19–21 Moreover, the absolute target of zero residual SA may not be the optimum to achieve the best visual outcomes.14,15 Consequently, a series of studies presented strategies for the calculation of customized aberration-correcting IOLs.27–29 Koch and Wang17 investigated the optimal amount of ocular SA to maximize optical quality in 154 eyes. They concluded that the optimal SA varies widely among individuals and that the selection of an aspheric IOL should be customized to the full spectrum of corneal HOAs and not just to the 4th-order SA.17

In the current study, we examined whether the implantation of an individual aspheric IOL can improve visual quality compared to a standardized SA-correcting lens. Preoperatively, we found an average total corneal SA (total of anterior and posterior corneal surface) for a 6-mm pupil of 0.31 ± 0.10 µm in the customized group and 0.34 ± 0.09 µm in the standardized group (total range for all eyes: 0.11 to 0.50 µm). Therefore, if the corneal SA is not measured and an aspherical IOL is selected randomly, the postoperative effect is likewise purely random. An important precondition for correction of aberrations in general is stability during surgery. In our study, preoperative corneal SA showed no significant changes in both groups over the 3-month follow-up (customized group: P = .061, standardized group: P = .167).

The postoperative ocular SA was analyzed for a diameter of 5 mm, because especially in the customized group only a few eyes achieved a dilated pupil diameter of 6 mm or greater. After 3 months, both groups had minimal total residual SA with slightly positive values in the customized group (0.04 ± 0.06 µm; range: −0.10 to 0.13 µm) and a slight overcorrection in the standardized group (−0.01 ± 0.05 µm; range: −0.14 to 0.06 µm). The results of the total ocular SA between 4 weeks and 3 months postoperatively were similar in both groups and the small differences were only visible after the calculation of four decimal places (Table B).

The optic design procedure applied for the calculation of the individual IOL optic not only aimed at a SA of zero, but also took the image quality in terms of modulation transfer function into account and considered a possible implant decentration of 0.3 mm. Werner et al.14 and Nochez et al.15 showed that a residual SA of +0.06 µm or +0.07 to +0.1 µm, respectively, may yield best contrast sensitivity results or provide the best compromise between depth of focus and best contrast sensitivity. It should also be noted that measuring the corneal SA is subject to variations30 and therefore an IOL perfectly compensating for the SA does not seem realistic. For this reason, a reduction of the corneal SA avoiding overcompensation was attempted in the design for the customized IOL optic. Future redefinition of the parameters included in the merit function may improve the results.

At 3 months postoperatively, outcomes regarding monocular UDVA and DCNVA were statistically significantly better in the customized group. Mean logMAR UDVA was 0.02 ± 0.07 in the customized group and 0.06 ± 0.10 in the standardized group. The difference between the groups is probably mainly related to the slight postoperative myopia in the standardized group (mean SE: −0.13 ± 0.39 D). Mean DCNVA in the customized group and standardized groups was 0.39 ± 0.14 and 0.49 ± 0.13 logMAR, respectively (P = .009). Overall, a DCNVA of 20/40 or better was achieved by 31% in the customized group and 19% in the standardized group, and 20/63 or better was achieved by 92% in the customized group and 58% in the standardized group. With regard to mean UNVA, UIVA (0.63 m), and DCIVA (0.63 m and 1 m), the customized group performed slightly better compared to the standardized group (despite the slight postoperative myopia in the standardized group), but without statistically significant differences. Only mean UIVA at 1 m was slightly better in the standardized group (0.10 ± 0.14 logMAR) compared to the customized group (0.13 ± 0.14 logMAR) (P = .312). CDVA was comparable between the groups (P = .759).

Song et al.31 investigated HOAs related to increased UNVA in eyes with aspheric monofocal IOLs. The authors concluded that in cases of aspheric IOL implantation, ocular vertical coma may be an important HOA associated with better near visual acuity.31 Although corneal aberrations are the most important determinants of total ocular aberrations after lens surgery, aberrations from internal optics can still play an essential role in visual performance.31

Regarding spherical equivalent, there was a statistically significant difference between the study groups at the 3-month visit (P = .007). In total, eyes from the standardized group tended toward slight myopia (mean: −0.13 ± 0.39 D), whereas the mean residual spherical equivalent in the customized group was slightly positive (mean: 0.13 ± 0.42 D). The refractive predictability was higher in the standardized group; 95.8% (customized group) and 96.2% (standardized group) of the eyes were within ± 1.00 D and 68.8% (customized group) and 84.6% (standardized group) within ±0.50 D of the targeted spherical equivalent. We believe that the difference in the smaller deviation range was mainly due to the robustness factor, which was implemented in the Invidua IOL calculation process to be more resistant to possible IOL tilt or decentration.2

Our results on postoperative defocus curves showed on average a larger defocus capacity in the customized group, particularly with regard to defocus levels from +2.00 to +0.50 D and from −2.00 to −3.00 D, where we found statistically significant differences between both groups. Additionally, it was noticeable that the defocus curve of the customized group showed a wider plateau from +0.50 to −0.50 D surrounding the distance focal point with a median visual acuity of 0.0 logMAR.

The results on contrast sensitivity were particularly remarkable. Median photopic and mesopic contrast sensitivity with and without glare source showed higher values in the customized group for all measured spatial frequencies. The differences were statistically significant with an exception for 18 cpd under mesopic conditions. These findings are in agreement with other studies16,32 showing that preoperative corneal SA measurement in patients with cataract followed by customized selection of aspherical IOL implants improves contrast sensitivity outcomes, especially under mesopic conditions and at high spatial frequencies. This underlines the superiority of an individualized selection strategy compared to a random selection of aspherical IOLs.

To optimize statistical comparability between the study groups, we performed a subgroup analysis. In the standardized subgroup, we included only eyes with a preoperative corneal SA of 0.27 ± 0.10 µm (in accordance with the SA-correcting effect of the Tecnis IOL) to simulate a preoperative selection. Furthermore, we excluded outliers in pupil diameter and SA in the customized group. This improved the comparability of the groups with regard to corneal SA (P = .778) and pupil diameter (P = .064). At 3 months, mean DCNVA was still statistically significantly better in the customized subgroup. The results on contrast sensitivity were not as clear as in our first analysis, but also showed distinct advantages in the customized subgroup across all lighting conditions and spatial frequencies.

Customization of aspheric IOLs may be especially desirable after corneal refractive surgery. In eyes after myopic ablation, SA increases in the positive direction, whereas hyperopic ablation induces a negative shift of the SA.33,34 In a recently published study, Whang et al.35 demonstrated the impact of axial length and anterior chamber depth on the effect of aspheric aberration-correcting IOLs. The authors showed that a relatively higher efficiency of aspheric IOL implantation is to be expected in shorter eyes and that not only the amount of compensating SA of the IOL but also the preoperative eye length should be considered.35 In another study, Langenbucher et al.2 concluded that the benefit with individually customized aspheric IOLs is less dependent on axial length. They described advantages in corneas with a moderate prolate shape and an equal or more negative Q value than the average of −0.22.

To our knowledge, this is the first study to compare the clinical outcomes of an individually customized and a standardized aberration-correcting IOL. The customized IOL showed potential to improve visual performance in lens surgery, especially with regard to contrast sensitivity. Future clinical studies with a greater number of cases and a longer follow-up are necessary to refine our results and to improve the merit function parameter set.

References

  1. Guo H, Goncharov AV, Dainty C. Comparison of retinal image quality with spherical and customized aspheric intraocular lenses. Biomed Opt Express. 2012;3:681–691. doi:10.1364/BOE.3.000681 [CrossRef]
  2. Langenbucher A, Janunts E, Seitz B, Kannengieser M, Eppig T. Theoretical image performance with customized aspheric and spherical IOLs— when do we get a benefit from customized aspheric design?Z Med Phys. 2014;24:94–103. doi:10.1016/j.zemedi.2013.05.001 [CrossRef]
  3. Piers PA, Manzanera S, Prieto PM, Gorceix N, Artal P. Use of adaptive optics to determine the optimal ocular spherical aberration. J Cataract Refract Surg. 2007;33:1721–1726. doi:10.1016/j.jcrs.2007.08.001 [CrossRef]
  4. Rocha KM, Vabre L, Harms F, Chateau N, Krueger RR. Effects of Zernike wavefront aberrations on visual acuity measured using electromagnetic adaptive optics technology. J Refract Surg. 2007;23:953–959. doi:10.3928/1081-597X-20071101-17 [CrossRef]
  5. Mester U, Dillinger P, Anterist N. Impact of a modified optic design on visual function: clinical comparative study. J Cataract Refract Surg. 2003;29:652–660. doi:10.1016/S0886-3350(02)01983-1 [CrossRef]
  6. Bellucci R, Scialdone A, Buratto L, et al. Visual acuity and contrast sensitivity comparison between Tecnis and AcrySof SA60AT intraocular lenses: a multicenter randomized study. J Cataract Refract Surg. 2005;31:712–717. doi:10.1016/j.jcrs.2004.08.049 [CrossRef]
  7. Schuster AK, Tesarz J, Vossmerbaeumer U. The impact on vision of aspheric to spherical monofocal intraocular lenses in cataract surgery: a systematic review with meta-analysis. Ophthalmology. 2013;120:2166–2175. doi:10.1016/j.ophtha.2013.04.011 [CrossRef]
  8. Mester U, Kaymak H. Comparison of the AcrySof IQ aspheric blue light filter and the AcrySof SA60AT intraocular lenses. J Refract Surg. 2008;24:817–825.18856237
  9. Awwad ST, Warmerdam D, Bowman RW, et al. Contrast sensitivity and higher order aberrations in eyes implanted with AcrySof IQ SN60WF and AcrySof SN60AT intraocular lenses. J Refract Surg. 2008;24:619–625. doi:10.3928/1081597X-20080601-12 [CrossRef]
  10. Casprini F, Balestrazzi A, Tosi GM, et al. Glare disability and spherical aberration with five foldable intraocular lenses: a prospective randomized study. Acta Ophthalmol Scand. 2005;83:20–25. doi:10.1111/j.1600-0420.2005.00378.x [CrossRef]
  11. Eppig T, Filser E, Goeppert H, et al. Index of contrast sensitivity (ICS) in pseudophakic eyes with different intraocular lens designs. Acta Ophthalmol. 2015;93:e181–e187. doi:10.1111/aos.12538 [CrossRef]
  12. Langenbucher A, Schröder S, Cayless A, Eppig T. Aberration-free intraocular lenses—what does this really mean?Z Med Phys. 2017;27:255–259. doi:10.1016/j.zemedi.2017.03.003 [CrossRef]
  13. Holladay JT, Piers PA, Koranyi G, Van der Mooren M, Norrby NC. A new intraocular lens design to reduce spherical aberration of pseudophakic eyes. J Refract Surg. 2002;18:683–691.12458861
  14. Werner JS, Elliott SL, Choi SS, Doble N. Spherical aberration yielding optimum visual performance: evaluation of intraocular lenses using adaptive optics simulation. J Cataract Refract Surg. 2009;35:1229–1233. doi:10.1016/j.jcrs.2009.02.033 [CrossRef]
  15. Nochez Y, Majzoub S, Pisella PJ. Effect of residual ocular spherical aberration on objective and subjective quality of vision in pseudophakic eyes. J Cataract Refract Surg. 2011;37:1076–1081. doi:10.1016/j.jcrs.2010.12.056 [CrossRef]
  16. Jia LX, Li ZH. Clinical study of customized aspherical intraocular lens implants. Int J Ophthalmol. 2014;7:816–821.25349799
  17. Koch DD, Wang L. Custom optimization of intraocular lens asphericity. Trans Am Ophthalmol Soc. 2007;105:36–41.
  18. Packer M, Fine IH, Hoffman RS. Aspheric intraocular lens selection based on corneal wavefront. J Refract Surg. 2009;25:12–20.19244948
  19. Beiko GH, Haigis W, Steinmueller A. Distribution of corneal spherical aberration in a comprehensive ophthalmology practice and whether keratometry can predict aberration values. J Cataract Refract Surg. 2007;33:848–858. doi:10.1016/j.jcrs.2007.01.035 [CrossRef]
  20. de Sanctis U, Vinai L, Bartoli E, Donna P, Grignolo F. Total spherical aberration of the cornea in patients with cataract. Optom Vis Sci. 2014;91:1251–1258. doi:10.1097/OPX.0000000000000380 [CrossRef]
  21. Schrecker J, Langenbucher A, Seitz B, Eppig T. First results with a new intraocular lens design for the individual correction of spherical aberration. J Cataract Refract Surg. 2018;44:1211–1219. doi:10.1016/j.jcrs.2018.06.055 [CrossRef]
  22. Eppig T, Scholz K, Loffler A, Messner A, Langenbucher A. Effect of decentration and tilt on the image quality of aspheric intraocular lens designs in a model eye. J Cataract Refract Surg. 2009;35:1091–100. doi:10.1016/j.jcrs.2009.01.034 [CrossRef]
  23. Zhao Y, Wang Z, Tian X, Wang X, Boa X. Comparative study of visual function and ocular aberrations of two different one-piece designed hydrophilic acrylic intraocular lens. Int Ophthalmol. 2018;38:1169–1175. doi:10.1007/s10792-017-0578-3 [CrossRef]
  24. Lasta M, Miháltz K, Kovács I, Vécsei-Marlovits PV. Effect of spherical aberration on the optical quality after implantation of two different aspherical intraocular lenses. J Ophthalmol. 2017;2017:8039719.28900544
  25. Kretz FT, Tandogan T, Khoramnia R, et al. High order aberration and straylight evaluation after cataract surgery with implantation of an aspheric, aberration correcting monofocal intraocular lens. Int J Ophthalmol. 2015;8:736–741.26309872
  26. Kretz FT, Son H, Liebing S, Tandogan T, Auffarth GU. Impact of an aspherical aberration correcting monofocal intraocular lens on patient satisfaction for daily life activities: the Heidelberg Daily Task Evaluation (DATE) questionnaire [article in German]. Klin Monbl Augenheilkd. 2015;232:940–946.26287539
  27. Einighammer J, Oltrup T, Feudner E, Bende T, Jean B. Customized aspheric intraocular lenses calculated with real ray tracing. J Cataract Refract Surg. 2009;35:1984–1994. doi:10.1016/j.jcrs.2009.05.053 [CrossRef]
  28. Langenbucher A, Eppig T, Seitz B, Janunts E. Customized aspheric IOL design by raytracing through the eye containing quadric surfaces. Curr Eye Res. 2011;36:637–646. doi:10.3109/02713683.2011.577265 [CrossRef]
  29. Zhu Z, Janunts E, Eppig T, Sauer T, Langenbucher A. Tomography-based customized IOL calculation model. Curr Eye Res. 2011;36:579–589. doi:10.3109/02713683.2011.566978 [CrossRef]
  30. de Jong T, Sheehan MT, Dubbelman M, Koopmans SA, Jansonius NM. Shape of the anterior cornea: comparison of height data from 4 corneal topographers. J Cataract Refract Surg. 2013;39:1570–1580. doi:10.1016/j.jcrs.2013.04.032 [CrossRef]
  31. Song IS, Kim MJ, Yoon SY, Kim JY, Tchah H. Higher-order aberrations associated with better near visual acuity in eyes with aspheric monofocal IOLs. J Refract Surg. 2014;30:442–446. doi:10.3928/1081597X-20140530-01 [CrossRef]
  32. Nochez Y, Favard A, Majzoub S, Pisella PJ. Measurement of corneal aberrations for customisation of intraocular lens asphericity: impact on quality of vision after micro-incision cataract surgery. Br J Ophthalmol. 2010;94:440–444. doi:10.1136/bjo.2009.167775 [CrossRef]
  33. Hersh PS, Fry K, Blaker JW. Spherical aberration after laser in situ keratomileusis and photorefractive keratectomy: clinical results and theoretical models of etiology. J Cataract Refract Surg. 2003;29:2096–2104. doi:10.1016/j.jcrs.2003.09.008 [CrossRef]
  34. Benito A, Redondo M, Artal P. Laser in situ keratomileusis disrupts the aberration compensation mechanism of the human eye. Am J Ophthalmol. 2009;147:424–431. doi:10.1016/j.ajo.2008.09.027 [CrossRef]
  35. Whang WJ, Piao J, Yoo YS, Joo CK, Yoon G. The efficiency of aspheric intraocular lens according to biometric measurements. PLoS One. 2017;12:e0182606. doi:10.1371/journal.pone.0182606 [CrossRef]

Preoperative Patient Demographics and Clinical Information

Parameter Customized Group Standardized Group P
Age (y) .044a
  Mean ± SD 68.9 ± 8.0 72.4 ± 6.1
  Median (range) 70 (50 to 84) 74 (59 to 81)
Gender, n (%) .025b
  Male 25 (52.1) 6 (23.1)
  Female 23 (47.9) 20 (76.9)
AL (mm) .772a
  Mean ± SD 23.21 ± 0.80 23.12 ± 1.00
  Median (range) 23.24 (21.44 to 25.06) 23.19 (20.98 to 24.91)
ACD (mm) .298a
  Mean ± SD 3.17 ± 0.35 3.07 ± 0.23
  Median (range) 3.18 (2.33 to 4.36) 3.13 (2.51 to 3.53)
Total corneal astigmatism (D) .774a
  Mean ± SD 0.46 ± 0.24 0.44 ± 0.24
  Median (range) 0.40 (0.00 to 0.90) 0.45 (0.10 to 0.90)
Total corneal SA Z40, 5-mm zone (µm) .132a
  Mean ± SD 0.138 ± 0.060 0.159 ± 0.061
  Median (range) 0.130 (−0.002 to 0.296) 0.158 (0.045 to 0.265)

3-Month Postoperative Monocular Visual Acuity and Refraction

Variable Customized Group Standardized Group P a
UDVA (logMAR) .046
  Mean ± SD 0.02 ± 0.07 0.06 ± 0.10
  Median (range) 0.00 (−0.10 to 0.22) 0.00 (−0.10 to 0.30)
UIVA 1.0 m (logMAR) .312
  Mean ± SD 0.13 ± 0.14 0.10 ± 0.14
  Median (range) 0.10 (−0.10 to 0.40) 0.10 (0.20 to 0.49)
UIVA 0.63 m (logMAR) .994
  Mean ± SD 0.22 ± 0.13 0.24 ± 0.17
  Median (range) 0.30 (−0.10 to 0.52) 0.20 (−0.10 to 0.70)
UNVA (logMAR) .171
  Mean ± SD 0.42 ± 0.17 0.47 ± 0.17
  Median (range) 0.40 (−0.10 to 0.92) 0.49 (0.10 to 0.80)
Cylinder (D) .750
  Mean ± SD 0.23 ± 0.27 0.20 ± 0.26
  Median (range) 0.00 (0.00 to 0.75) 0.00 (0.00 to 0.75)
SE (D) .007
  Mean ± SD 0.13 ± 0.42 −0.13 ± 0.39
  Median (range) 0.00 (−0.88 to 1.38) 0.00 (−0.88 to 0.88)
CDVA (logMAR) .759
  Mean ± SD −0.02 ± 0.04 −0.01 ± 0.04
  Median (range) 0.00 (−0.10 to 0.00) 0.00 (−0.10 to 0.10)
DCIVA 1.0 m (logMAR) .545
  Mean ± SD 0.08 ± 0.10 0.09 ± 0.11
  Median (range) 0.10 (−0.10 to 0.30) 0.10 (−0.20 to 0.40)
DCIVA 0.63 m (logMAR) .096
  Mean ± SD 0.20 ± 0.12 0.25 ± 0.11
  Median (range) 0.20 (−0.10 to 0.40) 0.30 (0.00 to 0.49)
DCNVA (logMAR) .009
  Mean ± SD 0.39 ± 0.14 0.49 ± 0.13
  Median (range) 0.40 (−0.10 to 0.70) 0.49 (0.30 to 0.70)

3-Month Postoperative Corneal and Ocular Spherical Aberration (µm)

Variable Customized Group Standardized Group P a
Corneal SA Z40
  5-mm zone .069
    Mean ± SD 0.13 ± 0.08 0.15 ± 0.06
    Median (range) 0.12 (−0.01 to 0.45) 0.16 (0.01 to 0.29)
Total ocular SA Z40
  5-mm zone < .001
    Mean ± SD 0.04 ± 0.06 −0.01 ± 0.05
    Median (range) 0.04 (−0.10 to 0.13) −0.01 (−0.14 to 0.06)
  5-mm zone, absolute value .101
    Mean ± SD 0.05 ± 0.04 0.04 ± 0.03
    Median (range) 0.05 (0.00 to 0.13) 0.04 (0.00 to 0.14)

4-Week Postoperative Monocular Visual Acuity and Refraction

Variable Customized Group Standardized Group
UDVA (logMAR)
  Mean ± SD 0.04 ± 0.09 0.09 ± 0.16
  Median (range) 0.00 (−0.10 to 0.30) 0.00 (−0.10 to 0.70)
UIVA 1.0 m (logMAR)
  Mean ± SD 0.15 ± 0.14 0.13 ± 0.12
  Median (range) 0.15 (−0.20 to 0.49) 0.10 (−0.10 to 0.40)
UIVA 0.63 m (logMAR)
  Mean ± SD 0.24 ± 0.15 0.23 ± 0.16
  Median (range) 0.30 (0.00 to 0.70) 0.20 (0.00 to 0.60)
UNVA (logMAR)
  Mean ± SD 0.43 ± 0.16 0.46 ± 0.18
  Median (range) 0.40 (0.10 to 0.92) 0.45 (0.10 to 0.80)
Cylinder (D)
  Mean ± SD 0.20 ± 0.25 0.22 ± 0.23
  Median (range) 0.00 (0.00 to 0.75) 0.25 (0.00 to 0.50)
SE (D)
  Mean ± SD 0.07 ± 0.41 −0.13 ± 0.41
  Median (range) 0.00 (−0.88 to 1.38) 0.00 (−1.13 to 0.88)
CDVA (logMAR)
  Mean ± SD 0.00 ± 0.03 0.00 ± 0.03
  Median (range) 0.00 (−0.10 to 0.10) 0.00 (−0.10 to 0.10)
DCIVA 1.0 m (logMAR)
  Mean ± SD 0.11 ± 0.09 0.13 ± 0.09
  Median (range) 0.10 (−0.10 to 0.30) 0.10 (−0.10 to 0.30)
DCIVA 0.63 m (logMAR)
  Mean ± SD 0.22 ± 0.12 0.26 ± 0.14
  Median (range) 0.20 (0.00 to 0.49) 0.30 (0.00 to 0.60)
DCNVA (logMAR)
  Mean ± SD 0.44 ± 0.12 0.48 ± 0.19
  Median (range) 0.40 (0.10 to 0.70) 0.49 (0.10 to 0.80)

Postoperative Corneal and Ocular Spherical Aberration (µm)

Variable 4 Weeks 3 Months P a


Customized Group Standardized Group Customized Group Standardized Group
Corneal SA Z40
  6-mm zone .075
    Mean ± SD 0.30 ± 0.11 0.35 ± 0.11 0.29 ± 0.12 0.33 ± 0.08
    Median (range) 0.29 (0.08 to 0.54) 0.35 (0.16 to 0.65) 0.28 (0.06 to 0.57) 0.32 (0.16 to 0.49)
  5-mm zone
    Mean ± SD 0.14 ± 0.07 0.16 ± 0.07
    Median (range) 0.13 (0.01 to 0.32) 0.15 (0.06 to 0.33)
Total ocular SA Z40
  5-mm zone
    Mean ± SD 0.04 ± 0.06 −0.01 ± 0.05
    Median (range) 0.05 (−0.07 to 0.15) −0.01 (−0.11 to 0.08)
  5-mm zone (4 decimal places) < .001
    Mean ± SD 0.0407 ± 0.0583 −0.0091 ± 0.0496 0.0360 ± 0.0552 −0.0138 ± 0.0507
    Median (range) 0.0450 (−0.0710 to 0.1510) −0.0060 (−0.1080 to 0.0830) 0.0380 (−0.1020 to 0.1270) −0.0080 (−0.1440 to 0.0600)
  5-mm zone, absolute value
    Mean ± SD 0.06 ± 0.04 0.04 ± 0.03
    Median (range) 0.05 (0.00 to 0.15) 0.04 (0.004 to 0.11)
Authors

From the Department of Ophthalmology, Rudolf Virchow Klinikum Glauchau, Glauchau, Germany (JS); Institute of Experimental Ophthalmology, Saarland University, Homburg/Saar, Germany (SS, AL, TE); the Department of Ophthalmology, Saarland University Medical Center, Homburg/Saar, Germany (BS); and AMIPLANT GmbH, Schnaittach, Germany (TE).

Dr. Schrecker received travel expenses from HumanOptics AG. Dr. Eppig received public funding from the German Federal Ministry of Economic Affairs and Energy and travel expenses from HumanOptics AG. The remaining authors have no financial or proprietary interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (JS, AL, TE); data collection (JS); analysis and interpretation of data (JS, SS, BS); writing the manuscript (JS); critical revision of the manuscript (SS, AL, BS, TE); statistical expertise (AL)

Correspondence: Jens Schrecker, MD, Rudolf Virchow Klinikum Glauchau, Virchowstraße 18, 08371 Glauchau, Germany. E-mail: jens. schrecker@t-online.de

Received: March 08, 2019
Accepted: August 14, 2019

10.3928/1081597X-20190814-02

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