Multifocal intraocular lenses (IOLs) have been used during cataract surgery for approximately 30 years, initially with only moderate success regarding patient satisfaction.1,2 The main reasons for dissatisfaction were postoperative blurred vision and the need for spectacles, especially in the intermediate range.3 Woodward et al.4 and deVries et al.5 investigated the causes of blurred vision and found posterior capsule opacification (PCO), ametropia, dry eye syndrome, and wavefront anomalies in most cases. Further developments focused on reduction of optical side effects and enhancement of the intermediate range, resulting in trifocal apodized IOLs.5–7
Whereas a spherical refractive error induces a shift of the range of perception (eg, +0.50 diopters [D] accentuates distance vision and weakens near vision), astigmatism degrades vision at any distance.8 IOL decentration of greater than 0.4 mm may induce coma with a significant impact on the quality of vision.9 Apodization of the IOL supports near vision due to the near reflex, but may increase and interfere with spherical aberration by intention.10–12 In contrast to other ocular wavefront errors, this aberration should not be compensated for during a potential re-treatment after implantation of apodized IOLs. Therefore, a selective treatment of ocular aberrations may be needed to increase the optical quality of eyes with multifocal IOLs. This is preferably carried out as laser in situ keratomileusis (LASIK), but surface ablation is also an option.13
In this retrospective cohort study, we evaluated patients who had cataract surgery including the implantation of a trifocal IOL and were dissatisfied with the result. To improve vision, we offered the patients a wavefront-guided selective aberration correction free of costs.
Patients and Methods
In this retrospective consecutive cohort, 213 eyes of 108 consecutive patients with phacoemulsification and implantation of a multifocal IOL between January 2015 and June 2017 were included. The average age of the patients at cataract surgery was 62.6 ± 7.5 years (range: 39 to 83 years) and the gender distribution was 55 women and 53 men.
Information about femtosecond laser–assisted cataract surgery (FLACS) plus potential LASIK and its risks and benefits was provided to each patient. Signed informed consent in accordance with the tenets of the Declaration of Helsinki was obtained, including that the patient's clinical information may be used for scientific studies. The institutional review board of the IROC approved this retrospective evaluation. LASIK preexamination was performed 1 month at the earliest after the second cataract surgery.
FLACS was performed under retrobulbar or topical anesthesia by the same experienced surgeon (TSeiler). All study participants received capsulotomy and lens fragmentation using the Z8 femtosecond laser (Ziemer, Port, Switzerland) and phacoemulsification was performed using the standard ultrasound technique (Megatron S4 HPS; Geuder, Heidelberg, Germany). The manually performed corneal incision was in the steepest meridian. Two fellow eyes were operated on at least 1 week apart, starting with the non-dominant eye. For IOL power calculation, the Haigis formula was used according to the measurements of axial length, corneal power, and anterior chamber depth measured by the IOLMaster 500 (Carl Zeiss Meditec, Jena, Germany) in all cases. The target for all eyes was emmetropia. The inclusion criteria were a preferably bilateral cataract surgery or refractive lens exchange with the implantation of a non-toric FineVision IOL (PhysIOL, Liége, Belgium), a corneal astigmatism of less than 2.50 D measured with corneal topography (Vario; Wavelight/Alcon, Erlangen, Germany), implantation of the IOL in the capsular bag, and a signed informed consent form. The non-toric FineVision IOL is a hydrophilic, biconvex aspheric trifocal diffractive lens with a spherical aberration of −0.11 µm. Patients were excluded from the study if they had ophthalmic surgery or pathology (including glaucoma), complications during cataract surgery, abnormal corneal shape, or endothelial cell count below 1,800/mm2. Patients suffering from dry eye interfering with visual acuity were treated until a corrected distance visual acuity (CDVA) of 20/25 was achieved or they were excluded from the study group. If an early opacification of the posterior capsule interfered with visual acuity, an Nd:YAG capsulotomy was performed with an optical zone in the pupillary plane of at least 5 mm in diameter.
Preoperatively and at 1, 3, and 12 months after LASIK surgery, all patients had a full ophthalmologic examination including refractive status, uncorrected distance visual acuity (UDVA), CDVA, uncorrected near visual acuity (UNVA) at 40 cm (visual acuities were tested under photopic conditions, at approximately 80 to 100 cd/m2), corneal topography (Vario) slit-lamp and eye fundus evaluation, and endothelial cell count analysis (SP-02; CSO, Scandicci Firenze, Italy).
Selective Wavefront-Guided LASIK
LASIK free of costs was offered to patients who were not fully satisfied at 1 month after the last cataract surgery at the earliest. Ocular wavefronts were measured using a commercial pyramid wavefront sensor (Peramis; SCHWIND eye-tech-solutions, Kleinostheim, Germany). This type of aberrometer employs 45,000 measuring points, resulting in a lateral resolution of the wavefront of approximately 10 µm. Figure 1A shows a typical wavefront depicting the concentric rings of different refractive zones. These complex wavefronts were approximated by Zernike polynomials allowing selective correction of different aberrations up to the 8th Zernike order. To support apodization, spherical aberrations of the 1st and 2nd order were not corrected. The multifocal and the apodization effect remained intact with this approach (Figure 1C). After export to the excimer laser (Amaris 1050; SCHWIND eye-tech-solutions), the appropriate ablation pattern was calculated with an optical zone of 6.5 mm. The LASIK flap with a thickness of 110 µm was created by a femtosecond laser (Z2; Ziemer). The target refraction was emmetropia, except in 3 non-dominant eyes where the patients preferred a target of −0.50 D.
Ocular wavefront analysis of an astigmatic eye 3 months after implantation of a trifocal intraocular lens with different simulated selective wavefront-guided corrections. (A) In the refractive chart (left), the concentric rings of different refractive zones are obvious. In the Zernike pyramid (center left), all aberrations up to the 8th order are listed. Major contributions are: spherical and astigmatic components (1st row) and coma (2nd row) and spherical aberration (3rd row). (B) Correction of all aberrations results in a nearly perfect point-spread function (right) and a homogenous wavefront (left). (C) Sparing the spherical aberrations of the 1st and 2nd order (left, red circles) leads to a more cloudy point-spread function (right) but supports the apodization of the intraocular lens.
Prior to LASIK and 1 year postoperatively, patients were asked to complete a short quality-of-vision questionnaire that included the following: (1) spectacle independence at any distance, (2) satisfaction with the current vision, and (3) the question: “Would you choose this procedure again?”
The statistical comparison of preoperative and postoperative satisfaction and preoperative and postoperative independence from spectacles was performed using the Wilcoxon rank test. To compare the preoperative and postoperative distribution of the refractive cylinder, we performed the Mann–Whitney U test. All calculations were performed with WinSTAT for Excel (R. Finch Software, 2015, Bad Kronzingen, Germany). A P value of less than .05 was considered statistically significant.
Fifty-six eyes of 42 patients out of a total of 213 eyes (56 eyes, 26%) received selective wavefront-guided LASIK after cataract surgery with implantation of a trifocal IOL. The time between the last cataract surgery and LASIK ranged from 4 weeks to 24 months, with an average of 6 months. Fourteen patients (28 eyes, 13%) had bilateral LASIK, 18 patients (18 eyes, 8%) had LASIK only in the dominant eye, and 10 patients (10 eyes, 5%) received LASIK only in the non-dominant eye.
Potential refractive reasons for patients' dissatisfaction are listed in Table 1; double nominations occurred. The predominant cause is obviously an astigmatism of greater than 0.50 D followed by myopia of −0.50 D or greater. In 7 eyes (12.5%), CDVA was reduced without apparent refractive reasons but all had increased higher order aberrations (HOAs).
Distribution of Optical Errors Causing Dissatisfaction
The LASIK surgery and the early postoperative follow-up visits were uneventful. One eye showed epithelial ingrowth at the 1-month follow-up visit that needed debridement. None of the eyes lost more than one Snellen line of CDVA (Figure 2). Figure 3 compares preoperative CDVA and postoperative UDVA; there was no apparent difference. There was also no significant difference between postoperative UDVA and CDVA. Binocular UNVA of 20/32 and better was achieved in all patients. Standard refractive charts demonstrated that targeted refraction was achieved in all but 1 eye (Figure 4). The refractive astigmatism was 0.50 D or less in 93% of the eyes after selective wavefront-guided LASIK compared to 38% before selective wavefront-guided LASIK (Figure 5) (P < .001). The HOAs were 0.53 ± 0.13 µm preoperatively and 0.39 ± 0.10 µm postoperatively. This difference was statistically significant (P = .01). In contrast, the spherical aberration changed from 0.13 ± 0.08 to 0.08 ± 0.10 µm, which was not statistically significant (P = .26). On questioning, none of the patients requested enhancement.
Difference in Snellen lines between corrected distance visual acuity (CDVA) after intraocular lens (IOL) implantation and CDVA after laser in situ keratomileusis (LASIK). No eye lost more than one Snellen line.
Cumulative Snellen visual acuity demonstrating safety of selective wavefront-guided laser in situ keratomileusis (LASIK) treatment. IOL = intraocular lens; CDVA = corrected distance visual acuity
Spherical equivalent refractive accuracy of selective wavefront-guided laser in situ keratomileusis (LASIK) treatment. The target refraction of ±0.50 diopters (D) and less was achieved in 98% of the eyes treated.
Refractive cylinder before and after selective wavefront-guided laser in situ keratomileusis treatment (LASIK). A cylinder of 0.50 diopters (D) and less was achieved in 93% of the eye treated. IOL = intraocular lens
Thirty-nine of the 42 patients with selective wavefront-guided LASIK responded to the questionnaire about the quality of daily vision. Patients rated the need for spectacles (near or far) on a scale of 1 (always) to 4 (never), with a mean score of 3.4 ± 1.0 prior to LASIK and 3.9 ± 0.3 at 1 year after selective wavefront-guided LASIK; this difference was statistically significant (P = .002). Four patients (10%) were using reading glasses rarely. The overall satisfaction with the current situation was rated on a scale of 1 (not at all) to 4 (fully satisfied) as 3.6 ± 0.8 after LASIK, with 3 patients (7%) being not at all (1 patient) or mainly not (2 patients) satisfied. Prior to LASIK, the mean score was 2.1 ± 0.8; this improvement was statistically significant (P < .001). The 1 patient who was not at all satisfied suffered from severe dry eye syndrome even 1 year after LASIK. The question “Would you choose the same procedure (trifocal IOL plus selective wavefront-guided LASIK) again?” was answered negatively by 4 patients (10%).
The major findings of this study were: (1) after implantation of trifocal IOLs during cataract surgery, 26% of the eyes needed additional refractive surgery to achieve more satisfying results; (2) residual astigmatism of greater than 0.50 D was the most common optical cause for dissatisfaction; and (3) adding selective wavefront-guided LASIK improved the rate of satisfaction significantly from 2.1 to 3.6 (out of 4).
Laser vision correction after multifocal IOL implantation to improve satisfaction has been proposed before.14,15 Alió et al. reported satisfying results in more than 88% of patients after implantation of multifocal (trifocal) IOLs only,16 and similarly high satisfaction levels were stated in other studies.17 In contrast, the Moorfields IOL Study Group found only 74% to 80% of their patients satisfied or nearly satisfied with the vision after multifocal IOL implantation.18 Comparable to the Moorfields study, 25% of our patients were dissatisfied enough to choose another surgery up to 24 months after FLACS, which is reflected by a mean score of only 2.1 (mainly not satisfied) before LASIK. The inclusion of eyes with preoperative astigmatism of up to −2.25 D, resulting in a higher refractive astigmatism after cataract surgery, might be one reason for this high percentage of dissatisfaction. The implantation of toric multifocal IOLs was an alternative, but a residual astigmatism of greater than 0.50 D was reported in up to 50% of such eyes.19,20 Intraoperative peripheral relaxing incisions, another alternative, appeared to be relatively unpredictable21 and both techniques may lead to the need for further enhancement surgery to achieve full correction.
De Vries et al.5 realized that the most common signs of dissatisfaction were blurred vision in 95% and photic phenomena in 38% of their cases and identified residual ametropia in 65%, posterior capsule opacification (PCO) in 16%, large pupil size in 14%, and wavefront anomalies in 12% of the eyes as causes for the subjective complaints. A similar prevalence of blurred vision and photic phenomena was found by Woodward et al.,4 but PCO occurred more frequently and ametropia accounted for only 29% of the eyes with blurred vision. In our series, PCO was not listed because an Nd:YAG capsulotomy, if necessary, preceded the decision of wavefront-guided LASIK. The clear majority of the eyes (63%) suffered from ametropia with astigmatism of greater than 0.50 D followed by myopia and hyperopia. We selected the threshold of disturbing astigmatism at 0.50 D because McNeely et al.22 showed that a refractive astigmatism of greater than 0.50 D significantly decreased UDVA after implantation of a multifocal IOL but had no impact on UNVA.22 On the other hand, Hayashi et al.8 found that a UNVA and UDVA of 20/40 can be achieved with an astigmatism of 1.00 D or less after multifocal IOL implantation, but in our social environment a UDVA of 20/40 would disqualify for a whole variety of activities.
Whether wavefront-guided or wavefront-optimized treatment is appropriate to correct residual optical errors after multifocal IOL-implantation has not been decided. Jendritza et al.14 distinguished between refractive and diffractive multifocal IOLs and recommended omitting wavefront-guided treatments in refractive multifocal IOLs because of significant visual losses. The same excimer laser system (VISX Star S4) was used by Muftuoglu et al.,23 who found no clear benefits of wavefront-guided treatments. Santhiago et al.24 believed that wavefront-optimized treatments are more relevant than wavefront-guided ablations. All publications refer to a wavefront measurement using a Hartmann-Shack sensor with a lateral resolution that is at least an order of magnitude smaller compared to the pyramid sensor used here. Therefore, the multi-focal effect is missed by the traditional sensors and may even create distortions as reported by Jendritza et al.14 In contrast, Figure 1A shows a typical ocular wavefront through a multifocal IOL. The concentric rings depicting different optical zones are clearly displayed. In our series, 12.5% of the eyes treated, similar to the percentage of the eyes analyzed by deVries et al.5 showed wavefront anomalies that were considered responsible for reduced vision. Those aberrations such as coma and astigmatism of higher order cannot be corrected by wavefront-optimized ablations.
The apodization of modern IOLs (like the FineVision used here) enhances the central power compared to the peripheral power of the IOL. The refraction of the eye gets more myopic with pupil constriction and, therefore, UNVA is improved by means of the near reflex. Optically, this apodization can be described as spherical aberrations and a total HOA correction, including spherical aberrations, would counteract if not compensate for this apodization (Figure 1B). However, other HOAs such as coma (created by tilt and decentration of the IOL) or higher order astigmatism (due to lens capsule fibrosis) should be corrected. The concept of selective wavefront-guided ablation correcting all aberrations except spherical aberrations of the 1st and 2nd order was followed in this study (Figure 1C).
The good results of previous studies on laser vision correction of standard refractive errors after multifocal IOL implantation, particularly the good correction of astigmatism,15,23 were confirmed by our study. Ninety-three percent of the eyes had a postoperative manifest astigmatism of 0.50 D or less (Figure 5) and 98% were within ±0.50 D of target refraction.
Alió et al.7 reviewed more than 100 articles on multifocal IOL implantation and found a global spectacle independence of 80% or more in only 48.7% of the patients. In our study, 96% of the patients reported total independence from glasses, and 4 patients used reading glasses occasionally, leading to an overall score of 3.9 ± 0.3 (out of 4). We attribute this excellent outcome to the results of selective wavefront-guided LASIK, which is also reflected by a significant increase of satisfaction with the current vision from 2.1 ± 0.8 before selective wavefront-guided LASIK to 3.6 ± 0.8 at 1 year and longer after selective wavefront-guided LASIK.
A limitation of the study is the fact that we offered LASIK for free and some patients might have not chosen the option of laser vision correction if they had to pay for it. Based on the good experience with this approach, we currently add one-quarter of a standard LASIK price to the package price of “multifocal IOL plus FLACS” and offer a potential selective wavefront-guided LASIK for “fine tuning” at no extra costs. This saves many discussions with patients and extra visits. Ideally, a comparative study including wavefront-guided LASIK with selective wavefront-guided LASIK would have given clearer evidence of whether selective wavefront-guided LASIK would be superior to wavefront-guided LASIK in apodized trifocal IOLs.
Based on a substantially improved wavefront acquisition technique, we present a new approach of selective wavefront-guided LASIK to improve satisfaction after implantation of trifocal IOLs. We could show that the refractive errors were reduced and spectacle independence and satisfaction increased significantly.
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Distribution of Optical Errors Causing Dissatisfaction
|Astigmatism > 0.50 D||35/56 (63%)|
|Myopia, SE < −0.25 D||25/56 (45%)|
|Hyperopia, SE > +0.25 D||11/56 (20%)|
|HOA > 0.5 µm||7/56 (13%)|