Journal of Refractive Surgery

Original Article Supplemental Data

SMILE Versus Implantable Collamer Lens Implantation for High Myopia: A Matched Comparative Study

Jakob Siedlecki, MD; Valerie Schmelter, MD; Wolfgang J. Mayer, MD, FEBO; Benedikt Schworm, MD; Siegfried G. Priglinger, MD, FEBO; Martin Dirisamer, MD, FEBO; Nikolaus Luft, MD, PhD, FEBO

Abstract

This article has been amended to include factual corrections. To read the erratum, click here. The online article and its erratum are considered the version of record.

PURPOSE:

To compare the safety, efficacy, and patient-reported quality of vision of small incision lenticule extraction (SMILE) and implantable Collamer lens (ICL) implantation for the treatment of high myopia.

METHODS:

A database of 1,634 SMILE (Carl Zeiss Meditec AG, Jena, Germany) and 225 ICL implantation (STAAR Surgical, Monrovia, CA) procedures was screened for patients with a binocular preoperative manifest refraction spherical equivalent between −6.00 and −10.00 diopters (D) and plano target refraction. One-to-one matching was performed by preoperative manifest refraction spherical equivalent, age, and pupil size. All identified patients were then prospectively examined at their next regular postoperative follow-up visit and presented with the standardized and clinically validated Quality of Vision questionnaire to gauge patient-reported postoperative visual quality.

RESULTS:

A total of 80 eyes (40 patients) were eligible for 1:1 matching. Mean postoperative follow-up was 27.8 ± 14.3 months in the SMILE group and 26.6 ± 17.7 months in the ICL group (P = .44). Regarding the percentage of eyes within ±0.50 D of plano target, refractive predictability was better in eyes treated with ICL implantation (90%) than SMILE (72.5%) (P = .045). Mean UDVA was comparable (ICL: −0.09 ± 0.10 logMAR; SMILE: −0.06 ± 0.09 logMAR; P < .09), but the efficacy (1.28 vs 1.05; P < .001) and safety (1.31 ± 0.22 vs 1.10 ± 0.25; P < .001) indices were higher after ICL implantation. ICL implantation induced significantly fewer higher order aberrations (total higher order aberrations: SMILE 0.724 ± 0.174 µm vs ICL 0.436 ± 0.114 µm; P < .01). Regarding subjective quality of vision, patients who had ICL implantation were significantly less bothered by visual disturbances, which were mainly halos after ICL and starbursts and fluctuations of vision after SMILE (P < .05).

CONCLUSIONS:

In this refraction-matched comparative study, ICL implantation for high myopia yielded better refractive accuracy, higher safety and efficacy indices, fewer higher order aberrations, and better subjective quality of vision than SMILE.

[J Refract Surg. 2020;36(3):150–159.]

Abstract

This article has been amended to include factual corrections. To read the erratum, click here. The online article and its erratum are considered the version of record.

PURPOSE:

To compare the safety, efficacy, and patient-reported quality of vision of small incision lenticule extraction (SMILE) and implantable Collamer lens (ICL) implantation for the treatment of high myopia.

METHODS:

A database of 1,634 SMILE (Carl Zeiss Meditec AG, Jena, Germany) and 225 ICL implantation (STAAR Surgical, Monrovia, CA) procedures was screened for patients with a binocular preoperative manifest refraction spherical equivalent between −6.00 and −10.00 diopters (D) and plano target refraction. One-to-one matching was performed by preoperative manifest refraction spherical equivalent, age, and pupil size. All identified patients were then prospectively examined at their next regular postoperative follow-up visit and presented with the standardized and clinically validated Quality of Vision questionnaire to gauge patient-reported postoperative visual quality.

RESULTS:

A total of 80 eyes (40 patients) were eligible for 1:1 matching. Mean postoperative follow-up was 27.8 ± 14.3 months in the SMILE group and 26.6 ± 17.7 months in the ICL group (P = .44). Regarding the percentage of eyes within ±0.50 D of plano target, refractive predictability was better in eyes treated with ICL implantation (90%) than SMILE (72.5%) (P = .045). Mean UDVA was comparable (ICL: −0.09 ± 0.10 logMAR; SMILE: −0.06 ± 0.09 logMAR; P < .09), but the efficacy (1.28 vs 1.05; P < .001) and safety (1.31 ± 0.22 vs 1.10 ± 0.25; P < .001) indices were higher after ICL implantation. ICL implantation induced significantly fewer higher order aberrations (total higher order aberrations: SMILE 0.724 ± 0.174 µm vs ICL 0.436 ± 0.114 µm; P < .01). Regarding subjective quality of vision, patients who had ICL implantation were significantly less bothered by visual disturbances, which were mainly halos after ICL and starbursts and fluctuations of vision after SMILE (P < .05).

CONCLUSIONS:

In this refraction-matched comparative study, ICL implantation for high myopia yielded better refractive accuracy, higher safety and efficacy indices, fewer higher order aberrations, and better subjective quality of vision than SMILE.

[J Refract Surg. 2020;36(3):150–159.]

The current consensus definition of high myopia is a spherical equivalent refractive error exceeding −6.00 diopters (D).1 Resulting from the current and projected myopia epidemic, 10% of the world's population are expected to suffer from high myopia by the year 2050.2 In regard to the surgical correction of high myopia, keratorefractive procedures and phakic intraocular lens implantation currently represent the most commonly pursued treatment strategies.

Posterior chamber phakic intraocular lens implantation (Visian Implantable Collamer Lens [ICL]; STAAR Surgical, Inc.; Monrovia, CA) has gained particular interest in recent years owing to the reversible nature of the technique, its wide range of refractive correction (up to −20.00 D of myopia), and recent improvements in lens design, such as the implementation of a central hole obviating the need for an iridotomy and significantly reducing the risk of anterior subcapsular cataract formation.3,4 Furthermore, clinical data have accumulated that confirm the implants' long-term refractive stability, safety, and efficacy profile.5,6 In contrast, the drawbacks of ICL implantation include variable endothelial cell loss4,7 and rare but non-negligible complications related to the intraocular nature of the procedure (eg, retinal detachment8 or endophthalmitis9).

On the other hand, keratorefractive laser procedures have a longer tradition in the correction of myopia, but entail certain disadvantages and risks that accumulate almost proportionally with increasing degrees of myopia. These include pronounced refractive regression10 and increased risk of ectasia.11 Moreover, keratorefractive treatments addressing high myopia by flattening of the central corneal curvature over a limited optical zone inevitably lead to a significant induction of corneal higher order aberrations (HOAs), thereby potentially compromising optical and subjective visual quality.11

Previous comparative studies between excimer laser–based keratorefractive procedures (ie, femtosecond laser–assisted in situ keratomileusis [FSLASIK] and photorefractive keratectomy [PRK]) and ICL implantation for correction of high myopia concordantly showed superior visual quality for the latter technique.10,12–14 Over the past 10 years, however, small incision lenticule extraction (SMILE) has been gaining increasing popularity as an alternative to excimer laser–based keratorefractive approaches in Europe, Asia, and the United States, where SMILE was approved by the U.S. Food and Drug Administration for the treatment of myopia in September 2016 and myopic astigmatism in October 2018. Compared to FSLASIK, SMILE has the potential to offer better preservation of corneal biomechanics,15 reduced iatrogenic dry eye symptoms,16,17 and larger functional optical zone sizes,18 and to better respect the natural asphericity of the cornea, which results in fewer surgically induced HOAs.19 For these reasons, the conclusions found in these previous comparative trials between excimer laser–based keratorefractive techniques and ICL implantation10,12–14 may not be directly transferable to SMILE. Moreover, none of these previous studies incorporated validated patient-reported outcome instruments to actually assess quality of vision as subjectively perceived by the patient.

The purpose of this study was to comprehensively compare the safety, efficacy, predictability, and patient-reported quality of vision of SMILE and ICL implantation for the treatment of high myopia exceeding −6.00 D.

Patients and Methods

Patient Selection and Matching

For the purpose of this cross-sectional study, our institution's database comprising 225 ICL implantations was screened for patients who underwent binocular ICL implantation for the correction of −6.00 to −10.00 D of manifest refraction spherical equivalent (MRSE) with plano target refraction. A further inclusion criterion was a minimum age of 18 years. Amblyopia defined as a preoperative corrected distance visual acuity (CDVA) of worse than 20/25 and any other condition of the anterior (eg, corneal scars or cataract) or posterior (eg, myopic maculopathy) ocular segment potentially limiting visual acuity or causing subjective visual disturbance were regarded as exclusion criteria. A total of 31 identified patients were matched by their mean MRSE of surgical correction to a corresponding patient who underwent SMILE with binocular plano target refraction, tolerating a maximum difference of −0.75 D of MRSE.

A total of 40 patients suitable for 1:1 matching were identified from our institution's keratorefractive database comprising a total of 1,634 SMILE procedures. All 40 identified patients were then prospectively clinically examined and presented with the Quality of Vision (QoV) questionnaire at their next regular postoperative follow-up visit (a minimum of 3 months postoperatively) as described in detail below. Because the employed QoV questionnaire was used in its original (English) form, patients with insufficient knowledge of the English language according to the investigators' judgment were ineligible for participating in the study. Institutional review board approval was obtained for all aspects of this study; consent to use their data for analysis and publication was obtained from all participants and all study-related procedures adhered to the tenets outlined in the Declaration of Helsinki.

SMILE

All SMILE procedures were performed by one of two highly experienced corneal surgeons (SGP, MD) using the VisuMax 500-kHz femtosecond laser system (Carl Zeiss Meditec AG, Jena, Germany). The technical principles of the SMILE procedure have been outlined in detail previously.20 In all cases, an optical zone of 6.5 mm was created. The intended cap diameter was 7.8 to 7.9 mm and the intended cap thickness ranged between 120 and 140 µm. For manual extraction of the refractive lenticule, a 4-mm incision was created by the femtosecond laser centered at the 135° position in right eyes and the 45° position in left eyes.21

Postoperatively, patients were prescribed dexamethasone 0.1% and tobramycin 0.3% eye drops six times daily for 1 week. Thereafter, dexamethasone 0.1% eye drops were tapered over the course of 1 month, starting with a four times daily regimen. Additionally, patients were encouraged to use preservative-free lubricating eye drops as often as individually required.

ICL Implantation

ICL power calculation was performed by the manufacturer in all cases using the proprietary online form ( https://evo-ocos.staarag.ch; version 4.08). ICL size was selected based on anterior chamber depth (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany) and horizontal corneal diameter (IOLMaster 500; Carl Zeiss Meditec AG). Only patients with an anterior chamber depth of 2.8 mm or greater as measured from the endothelium with a Scheimpflug device (Pentacam HR) and a preoperative endothelial cell density of 2,000 cells/mm2 or greater as assessed by specular microscopy (CEM-530; NIDEK Inc., Gamagori, Japan) were eligible for ICL implantation.

All ICL implantations were performed by a single highly experienced intraocular surgeon (SGP) via a 2.8-mm temporal incision. The ICL implants featured a 0.36-mm central hole and the mean implant diameter was 13.08 ± 0.24 mm. A total of 21 (52.5%) ICLs of 12 (60%) patients were toric implants. For correct alignment of toric ICLs, preoperative corneal marking of the desired axis was conducted by the surgeon at the slit lamp with two opposing limbal marks placed with a bubble marker. The postoperative drop regimen was identical to the drop regimen after SMILE.

Subjective Refraction and Visual Acuity Readings

Subjective manifest and cycloplegic refraction was measured using the Jackson cross-cylinder method. Monocular and binocular uncorrected distance visual acuity (UDVA) and CDVA was determined using standard Early Treatment Diabetic Retinopathy Study charts at 4 meters.

Corneal Tomography and Hoas

Preoperative and postoperative corneal tomography scans were obtained using a high-resolution rotating Scheimpflug camera system (Pentacam HR). All measurements were obtained under standard scotopic ambience light conditions and participants had to refrain from using eye drops 1 hour prior to scanning. For the current analysis, total (anterior + posterior) corneal HOAs were calculated for the central 6-mm zone using the Optical Society of America notation. Root mean square values were automatically calculated by the system's onboard software for spherical aberration (Z04), coma (Z13, Z−13), trefoil (Z33, Z−33), and total HOAs.

Patient-Reported Quality of Vision

All patients were presented with the original English version of the Quality of Vision (QoV) questionnaire developed by McAlinden et al.22 The questionnaire represents a validated, standardized instrument that has been used in several other studies for the assessment of QoV after SMILE,23 LASIK,24 and intraocular lens implantation.25 The questionnaire encompasses 10 different items of visual disturbance: glare, halos, starbursts, hazy vision, blurred vision, distortion, double or multiple images, fluctuation in vision, focusing difficulty, and difficulty judging distance/with depth perception. All but the latter three symptoms are illustrated by standardized color images (the so-called “QoV Pictures” printed in standardized size: 163 × 232 mm, 300 × 300 DPI). The questionnaire evaluates QoV in three dimensions: patients are encouraged to report how often (never [0], occasionally [1], quite often [2], very often [3]) and how severe (not at all [0], mild [1], moderate [2], severe [3]) they experienced the respective symptoms and how much they were bothered by them (not at all [0], a little [1], quite [2], very [3]). After entering all data into a spreadsheet, three separate QoV scores were calculated by the inventor for the respective dimensions of visual disturbance (frequency, severity, and bothersomeness). Incorporating all 10 tested visual symptoms, the proprietary QoV scores represent linear-scaled measures of the three dimensions of visual disturbance in general and can range from 0 (no disturbance) to 100 (maximum disturbance).

Statistical Analysis

All statistical analysis was performed using SPSS for Windows software (version 25.0.1; IBM Corporation, Armonk, NY). Unless indicated otherwise, all data are reported as mean ± standard deviation. Normality of data was examined by histogram frequency analysis and the Shapiro-Wilk test. Independent-samples t tests were employed to compare the following normally distributed parameters between groups: preoperative keratometry readings, mesopic pupil size, and postoperative manifest refraction. The Mann–Whitney U test was used to compare the following non-normally distributed parameters between groups: patient age, preoperative manifest refraction, preoperative CDVA, angle kappa, follow-up time, safety and efficacy index, postoperative manifest cylinder, postoperative UDVA, and QoV scores. The chi-square test was used to compare fractions of eyes achieving a certain level of postoperative visual or refractive outcome (eg, eyes with UDVA of 20/16 or better or eyes within ±0.50 D from plano refraction) between groups. The safety index was defined as the ratio of monocular postoperative CDVA to monocular preoperative CDVA. The efficacy index was defined as the ratio of monocular postoperative UDVA to monocular preoperative CDVA. A P value of less than .05 was defined as indicative of statistical significance.

Results

The patients' baseline characteristics are summarized in Table 1. The SMILE group comprised 10 women and 10 men and the ICL subgroup consisted of 15 women and 5 men. Preoperatively, there was no statistically significant difference between groups regarding manifest sphere (P = .98) and MRSE (P = .196). However, patients in the SMILE group showed lower amounts of manifest cylinder (P = .01), exhibited statistically significant flatter keratometry readings (P < .05), and achieved superior CDVA (P = .01). No intra-operative or postoperative complications occurred in either group.

Baseline Characteristics of the SMILE and ICL Groups

Table 1:

Baseline Characteristics of the SMILE and ICL Groups

Safety

No eye lost two or more lines of CDVA in either group (Figure 1). Twenty percent of eyes in the SMILE group lost one line, whereas no eye in the ICL group lost any CDVA. Accordingly, the safety index was statistically significantly higher in the ICL (1.31 ± 0.22) than in the SMILE (1.10 ± 0.25) group, as assessed with the Mann–Whitney U test (P < .001).

Comparison of procedural safety between (A) small incision lenticule extraction (SMILE) and (B) implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA) for the correction of high myopia. No eye lost two or more lines of corrected distance visual acuity (CDVA) in either group. Twenty percent of eyes in the SMILE group and no eye in the ICL group lost one line. The safety index was significantly higher after ICL implantation than SMILE (1.31 ± 0.22 vs 1.10 ± 0.25; P < .001).

Figure 1.

Comparison of procedural safety between (A) small incision lenticule extraction (SMILE) and (B) implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA) for the correction of high myopia. No eye lost two or more lines of corrected distance visual acuity (CDVA) in either group. Twenty percent of eyes in the SMILE group and no eye in the ICL group lost one line. The safety index was significantly higher after ICL implantation than SMILE (1.31 ± 0.22 vs 1.10 ± 0.25; P < .001).

Efficacy

Preoperatively, 53% of SMILE eyes and 10% of ICL eyes yielded a CDVA of 20/16 or better (P < .001; Figure 2). Mean postoperative UDVA was comparable between the SMILE (−0.06 ± 0.09 logMAR) and ICL (−0.09 ± 0.10 logMAR) groups (P = .09). However, significantly more ICL eyes (68%) than SMILE eyes (43%) achieved UDVA of 20/16 or better (P = .025) postoperatively. The efficacy index was also significantly higher in the ICL (1.28 ± 0.24) than in the SMILE (1.05 ± 0.25) group, as assessed with the Mann–Whitney U test (P < .001).

Comparison of efficacy between (A) small incision lenticule extraction (SMILE) and (B) implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA) for high myopia. In the ICL group, more eyes achieved an uncorrected distance visual acuity (UDVA) of 20/16 or better (68% vs 43%; P = .025). The efficacy index was higher after ICL implantation than SMILE (1.28 vs 1.05; ±0.25). corrected distance visual acuity (CDVA).

Figure 2.

Comparison of efficacy between (A) small incision lenticule extraction (SMILE) and (B) implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA) for high myopia. In the ICL group, more eyes achieved an uncorrected distance visual acuity (UDVA) of 20/16 or better (68% vs 43%; P = .025). The efficacy index was higher after ICL implantation than SMILE (1.28 vs 1.05; ±0.25). corrected distance visual acuity (CDVA).

Refractive Outcome

There was no statistically significant difference (P = .27) in postoperative MRSE between the SMILE (−0.26 ± 0.41 D) and ICL (−0.17 ± 0.33 D) groups. The standard graphs for reporting spherical and astigmatic predictability are shown in Figures 35. All eyes in either group lay within ±1.00 D of plano. However, ICL implantation yielded a significantly higher amount of eyes within ±0.50 D of plano (90%) compared with SMILE (73%, P = .045). There was no difference in postoperative mean residual cylinder (SMILE −0.51 ± 0.28 D vs ICL −0.58 ± 0.32 D; P = .36) nor in the ±0.50 and ±1.00 D astigmatic accuracy (Figure 5).

Comparison of refractive accuracy, attempted versus achieved spherical equivalent refraction for (A) small incision lenticule extraction (SMILE) and (B) implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA). Both groups showed slight undercorrection, but all eyes in either group were within ±1.00 diopter (D) from plano.

Figure 3.

Comparison of refractive accuracy, attempted versus achieved spherical equivalent refraction for (A) small incision lenticule extraction (SMILE) and (B) implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA). Both groups showed slight undercorrection, but all eyes in either group were within ±1.00 diopter (D) from plano.

Comparison of distribution of manifest spherical equivalent refraction for (A) small incision lenticule extraction (SMILE) and (B) implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA). All eyes in either group lay within ±1.00 diopter (D) from plano. ICL implantation yielded a significantly higher amount of eyes within ±0.50 D from plano as compared with SMILE (90 vs 73%, P = .045).

Figure 4.

Comparison of distribution of manifest spherical equivalent refraction for (A) small incision lenticule extraction (SMILE) and (B) implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA). All eyes in either group lay within ±1.00 diopter (D) from plano. ICL implantation yielded a significantly higher amount of eyes within ±0.50 D from plano as compared with SMILE (90 vs 73%, P = .045).

Comparison of refractive astigmatic accuracy. There was no difference between both groups concerning residual cylinder ([A] small incision lenticule extraction [SMILE] −0.51 ± 0.28 diopters [D] vs [B] implantable Collamer lens implantation [ICL] [Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA] −0.58 ± 0.32 D; P = .36) or the percentage of eyes with ±0.50 and ±1.00 D astigmatism.

Figure 5.

Comparison of refractive astigmatic accuracy. There was no difference between both groups concerning residual cylinder ([A] small incision lenticule extraction [SMILE] −0.51 ± 0.28 diopters [D] vs [B] implantable Collamer lens implantation [ICL] [Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA] −0.58 ± 0.32 D; P = .36) or the percentage of eyes with ±0.50 and ±1.00 D astigmatism.

HOAs

An overview of the preoperative, postoperative, and induced HOAs is given in Table 2. Preoperatively, both groups did not differ concerning spherical aberration, coma, trefoil, or root mean square HOAs (P ≥ .12 for all comparisons). Postoperatively, eyes treated with SMILE showed significantly higher amounts of spherical aberration, coma, and total HOAs than the ICL group (P < .001), which also resulted in a significantly higher delta of induced spherical aberration, coma, and total HOAs attributable to the surgical method (P < .001 for all comparisons).

Comparison of Preoperative and Postoperative HOAs After SMILE and ICL Implantation

Table 2:

Comparison of Preoperative and Postoperative HOAs After SMILE and ICL Implantation

Patient-Reported QoV

Table 3 summarizes the three linear-scaled QoV scores. There was no statistically significant difference in visual symptom frequency (P = .12) and severity (P = .83). The bothersomeness score was significantly lower in patients after ICL implantation (16.5 ± 14.1) than after SMILE (25.9 ± 14.5; P = .002), indicating less overall irritation due to visual disturbances in the former group.

Linearized Outcomes of the QoV Questionnaire Comparing Subjective Visual Function After SMILE and ICL Implantation

Table 3:

Linearized Outcomes of the QoV Questionnaire Comparing Subjective Visual Function After SMILE and ICL Implantation

Stacked histogram plots giving a detailed representation of the frequency, severity, and bothersomeness of the 10 specific visual symptoms are presented in Figure A (available in the online version of this article). Fluctuations in vision was the most commonly reported, most severely perceived, and most bothersome long-term visual symptom after SMILE. In contrast to a prevalence of 80% in SMILE patients, only 60% of ICL patients reported fluctuations in vision, which was the third most commonly perceived symptom in this group. Starburst was the second most common symptom after SMILE experienced by 65% of patients as opposed to only 30% in the ICL group, where starburst ranked as the fifth most commonly perceived symptom (Figure A).

Stacked histogram plots on the frequency, severity, and bothersomeness of the ten specific visual symptoms after small incision lenticule extraction (SMILE) and implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA).

Figure A.

Stacked histogram plots on the frequency, severity, and bothersomeness of the ten specific visual symptoms after small incision lenticule extraction (SMILE) and implantable Collamer lens (ICL) implantation (Visian Implantable Collamer Lens; STAAR Surgical, Monrovia, CA).

In the ICL group, halos were the leading visual symptom reported by 80% of patients. In SMILE patients, however, halos showed a prevalence of only 35%. After ICL implantation, halos were also the leading symptom regarding severity and bothersomeness, with 45% of ICL patients feeling bothered due to halos. In contrast, halos bothered only 20% of SMILE patients.

Discussion

The current study is the first to comprehensively analyze and compare the safety, efficacy, and subjective patient-reported QoV after SMILE and ICL implantation for the surgical correction of high myopia exceeding −6.00 D.

Both methods showed favorable safety with no clinically significant intraoperative or postoperative complications and no eye of either group losing two or more lines of CDVA over a mean follow-up of more than 2 years. Nevertheless, ICL implantation exhibited a slightly superior safety profile.

With respect to treatment efficacy, we detected comparably excellent mean levels of UDVA in both groups. Interestingly, however, ICL implantation yielded a superior efficacy index, despite the fact that baseline CDVA was worse in the ICL group. These superior visual outcomes achieved by ICL implantation may be directly related to the technique's superior refractive accuracy observed in the current study. Even though comparable levels of MRSE were achieved in both groups, SMILE showed a stronger tendency toward refractive undercorrection. On the other hand, the observed superior unaided visual outcome after ICL implantation may also be related to its favorable aberrometric control with virtually no corneal HOAs being induced. In contrast, SMILE induced significant total corneal HOAs, with coma and spherical aberration being the predominant polynoms.

Multiple studies comparing FS-LASIK or PRK with ICL implantation for high myopia have concordantly shown similar results. In these studies, ICL implantation showed higher safety and efficacy indices,10 a lower induction of HOAs,10,12,14 and better contrast sensitivity12,14 than keratorefractive surgery. It may be hypothesized that these shortcomings of keratorefractive surgery compared with ICL implantation in high myopia might be ameliorated by SMILE due to certain technical advantages of this entirely femtosecond laser–based technique over traditional excimer laser–based keratorefractive approaches. These include the potential to offer a better preservation of corneal biomechanics,15 reduced iatrogenic dry eye symptoms,16,17 larger functional optical zone sizes,18 and improved preservation of the natural asphericity of the cornea, thereby resulting in fewer surgically induced HOAs.19

Nevertheless, the current results suggest that SMILE offers good refractive and visual outcomes in the treatment of high myopia, but is still subpar when directly compared to a refraction-matched sample of eyes treated with ICL implantation. Ultimately, it remains unclear as to whether these slight differences in objective functional outcomes can translate into evidence-based clinical recommendations for patients with high myopia seeking surgical correction of their refractive error.

Patient-reported subjective outcome instruments have become an increasingly popular and politically demanded tool for the evaluation of interventions in medicine.26 The current study employed the standardized, Rasch-tested, and clinically established QoV questionnaire to gauge patients' subjectively perceived QoV.22 The three primary outcome measures of the 30-item questionnaire (the QoV scores) represent comprehensive indices of overall symptom frequency, severity, and bothersomeness, respectively. We observed comparable frequency and severity QoV scores after SMILE and ICL implantation; however, overall disturbance due to visual phenomena was significantly less bothersome in the ICL group. This finding could be due to the fact that each technique evoked a specific spectrum of visual symptoms: fluctuations in vision and starburst were the most commonly reported visual symptoms after SMILE with a long-term prevalence of 85% and 65%, respectively. In contrast, patients in the ICL group perceived a prevalence of only 60% and 30%, respectively. Halos were the leading visual symptom after ICL implantation, with a prevalence of 80% as opposed to only 35% in patients after SMILE. Ring-shaped dysphotopsia, or halos, are well-known phenomena after ICL implantation caused by stray light refracted from the hole incorporated in the center of the lens optic.27 It appears that the dissimilar spectra of visual symptoms perceived by patients after SMILE and ICL implantation are less bothersome in the latter group.

We believe that the slightly advantageous objective visual performance of ICL implantation over SMILE in conjunction with our findings regarding subjectively perceived visual quality should affect our clinical decision making and counseling of patients seeking surgical correction of high myopia. Of note, our group recently showed that very good preoperative CDVA (of 20/12.5 or better) can also be a risk factor for experiencing more bothersome visual symptoms after SMILE.23 Hence, ICL implantation may be particularly advantageous over SMILE in those patients with high myopia who exhibit paramount preoperative visual acuity.

This study is mainly limited by its cross-sectional design. A prospective, randomized study seems warranted to further analyze and balance the advantages and drawbacks of SMILE and ICL implantation in high myopia. As a further limitation, the maximum amount of MRSE included in this study was −10.00 D because of the National Refractive Surgery Committee's (Kommission Refraktive Chirurgie) guidelines restricting the application of SMILE to a myopic range of −1.00 to −10.00 D. In addition, the amount of cylindrical correction was not matched between groups and the ICL group exhibited significantly higher preoperative astigmatism. Postoperatively, however, there was no difference in mean residual cylinder nor in the ±0.50 or ±1.00 D astigmatic accuracy. Moreover, both eyes of all patients were included, which could be regarded as a weakness of this analysis. However, the binocular design and validation of the employed questionnaire for scoring subjective visual quality as perceived in daily life inevitably necessitated the inclusion of both eyes from each patient. A strength of the study is its comprehensive methodology in an effort to compare several aspects of visual outcome after refractive surgery, including objective and subjective outcome parameters.

ICL implantation offered slightly superior safety, efficacy, refractive predictability, induced fewer corneal HOAs, and resulted in less bothersome visual disturbances compared with SMILE and may, thus, represent a better option for patients with high myopia, particularly those who exhibit very good preoperative spectacle-corrected visual acuity.

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Baseline Characteristics of the SMILE and ICL Groups

ParameterSMILE (40 Eyes, 20 Patients)ICL (40 Eyes, 20 Patients)P


Mean ± SDRangeMean ± SDRange
Female/male ratio10:1015:5
Age (years)32.2 ± 7.623 to 4933.9 ± 6.423 to 46.22
Preoperative manifest sphere (D)−7.34 ± 0.92−6.00 to −9.75−7.28 ± 1.25−4.25 to −9.25.98
Preoperative manifest cylinder (D)−0.86 ± 0.640.00 to −2.25−1.53 ± 1.040.00 to −4.25< .01
Preoperative MRSE (D)−7.78 ± 0.80−6.63 to −9.88−8.04 ± 1.05−6.13 to −9.63.196
Preoperative CDVA (logMAR)−0.05 ± 0.050.00 to −0.200.01 ± 0.080.00 to −0.20< .01
K flat (mm)7.84 ± 0.277.17 to 8.377.73 ± 0.197.27 to 8.08.04
K steep (mm)7.65 ± 0.296.96 to 8.297.47 ± 0.237.03 to 7.90< .01
K mean (mm)7.70 ± 0.287.05 to 8.137.60 ± 0.207.23 to 7.96.07
K maximum (D)44.74 ± 1.5942.00 to 48.9045.71 ± 1.4543.40 to 49.00< .01
Mesopic pupil size (mm)3.61 ± 0.732.20 to 5.123.48 ± 0.512.53 to 4.87.38
Angle kappa (mm)0.20 ± 0.110.03 to 0.530.18 ± 0.110.01 to 0.61.47
Follow-up time (months)27.8 ± 14.34.9 to 49.426.6 ± 17.73.5 to 68.8.44

Comparison of Preoperative and Postoperative HOAs After SMILE and ICL Implantation

HOAsSMILEICLP


Mean ± SDRangeMean ± SDRange
Preoperative
  Spherical aberration (µm)0.220 ± 0.0770.044 to 0.4600.209 ± 0.0840.051 to 0.410.53
  Coma (µm)0.154 ± 0.0920.021 to 0.4000.220 ± 0.1560.027 to 0.599.08
  Trefoil (µm)0.100 ± 0.0590.016 to 0.2420.078 ± 0.0450.008 to 0.183.15
  Total HOAs (µm)0.352 ± 0.0800.229 to 0.5970.388 ± 0.1100.220 to 0.652.12
Postoperative
  Spherical aberration (µm)0.443 ± 0.1350.146 to 0.6980.249 ± 0.0890.051 to 0.408< .001
  Coma (µm)0.433 ± 0.081−0.181 to 0.1640.202 ± 0.1530.011 to 0.571< .001
  Trefoil (µm)0.119 ± 0.0600.016 to 0.2350.101 ± 0.0610.010 to 0.290.19
  Total HOAs (µm)0.724 ± 0.1740.396 to 1.1860.436 ± 0.1140.252 to 0.652< .001
Induced
  Spherical aberration (µm)0.223 ± 0.132−0.123 to 0.4430.040 ± 0.066−0.102 to 0.168< .001
  Coma (µm)0.279 ± 0.180−0.216 to 0.703−0.018 ± 0.072−0.201 to 0.177< .001
  Trefoil (µm)0.019 ± 0.081−0.181 to 0.1640.023 ± 0.069−0.085 to 0.192.78
  Total HOAs (µm)0.372 ± 0.1870.070 to 0.9080.048 ± 0.080−0.082 to 0.275< .001

Linearized Outcomes of the QoV Questionnaire Comparing Subjective Visual Function After SMILE and ICL Implantation

QoV ScoreSMILEICLP
Frequency
  Mean ± SD35.0 ± 14.031.7 ± 10.2.12
  Median37.037.0
  Range0 to 5615 to 45
  IQR1315
Severity
  Mean ± SD28.6 ± 11.728.8 ± 9.4.83
  Median29.532.0
  Range0 to 4413 to 43
  IQR1213
Bothersomeness
  Mean ± SD25.9 ± 14.516.5 ± 14.1.002
  Median29.018.5
  Range0 to 460 to 42
  IQR1428
Authors

From University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany (JS, VS, WJM, BS, SGP, MD, NL); and SMILE Eyes Clinic, Linz, Austria (JS, WJM, SGP, MD, NL).

Dr. Siedlecki received speaker fees and travel expenses from Novartis Pharma GmbH, Carl Zeiss Meditec AG, Oculentis OSD Medical GmbH, and Pharm-Allergan GmbH; and personal consultation fees from Bayer AG. Dr. Mayer received previous financial, consultation, and speaker fee support from Carl Zeiss Meditec AG, Alcon Pharma GmbH, and Ziemer Ophthalmology GmbH; financial and speaker fee support from Novartis Pharma GmbH, Oculentis OSD Medical GmbH, Pharm-Allergan GmbH, and Bausch & Lomb GmbH; and speaker fees from Heidelberg Engineering GmbH, Oertli AG, and STAAR Surgical AG. Dr. Schworm received speaker fees and travel expenses from Novartis Pharma GmbH and Topcon Corporation. Dr. Priglinger received speaker fees and/or travel expenses from Novartis Pharma GmbH, Oertli AG, Bayer AG, Alcon Pharma GmbH, and Pharm-Allergan GmbH. Dr. Luft received income from honoraria as a lecturer from Alcon Laboratories, Inc., NIDEK Co. Ltd, and CenterVue SpA. The remaining authors have no proprietary or financial interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (JS, NL); data collection (JS, VS, WJM, BS, SGP, MD, NL); analysis and interpretation of data (JS, VS, NL); writing the manuscript (JS, NL); critical revision of the manuscript (JS, VS, WJM, BS, SGP, MD, NL); statistical expertise (JS); administrative, technical, or material support (SGP, MD); supervision (SGP, MD)

Correspondence: Nikolaus Luft, MD, PhD, FEBO, University Eye Hospital, Ludwig-Maximilians-University, Mathildenstrasse 8, 80336 Munich, Germany. E-mail: nikolaus.luft@med.uni-muenchen.de

Received: October 26, 2019
Accepted: February 10, 2020

10.3928/1081597X-20200210-02

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