Comparison of Subjective and Objective Visual Quality of Two Main Types of Refractive Surgeries in Early Postoperative Stage

doi:10.21203/rs.3.rs-4154525/v1

Purpose:

To explore subjective and objective visual quality of patients who underwent laser refractive surgery and ICL implantation in early postoperative stage after adjusting the imbalance of the baseline characteristics.

Methods:

This retrospective study included 58eyes with myopia and myopic astigmatism who underwent ICL V4c implantation or laser refractive surgery (including SMILE and FS-LASIK) in our hospital from July 2022 to December 2021. Objective visual quality mainly including higher-order aberrations (HOAs) were measured using an OPD-Scan III aberrometer (Nidek Co., Ltd., Gamagori, Japan) preoperatively and 1 week postoperatively. The subjective visual quality was obtained through the Quality of Vision (QoV) questionnaire. The propensity score inverse probability of treatment weighting (PS-IPTW) was used to balance the baseline characteristics.

Results:

After IPTW, the confounding factors with statistical significance between laser refractive surgery group and ICL implantation group. Before IPTW, the objective visual quality of laser refractive surgery was better than ICL implantation. However, after IPTW, only spherical aberration(p＝0.023) is statistically different between two groups. The patients who underwent laser refractive surgery reported better subjective visual quality in frequency(p＝0.020), severity(p＝0.043) and bothersome(p＝0.002). But two groups showed no significant difference after IPTW.

Conclusion:

The subjective and objective visual quality of patients who underwent laser refractive surgery and ICL implantation are relatively similar in early postoperative stage. The better subjective and objective visual quality in laser refractive surgery than ICL implantation could be influenced by imbalanced baseline characteristics.

Refractive surgery

ICL implantation

Visual quality

Higher-order aberrations

Myopia has become a global health issue over the past half century, for its impact on life quality and threat to human vision.^1–3 Evidences suggests that the population with myopia will rise to about 5 billion and 20% of them are patients with high myopia by 2050.⁴ One of the most disturbing affects caused by myopia is the decrease of visual quality, which is negatively related to refractive error.⁵ Despite the wide application of refractive surgeries, numbers of patients with myopia suffers the burden of poor visual quality before and after operations.

Based on the mechanism of myopia correction, current refractive surgery can be approximately divided into two types: laser refractive surgery and ICL Implantation. The former mainly use laser to sculpt the central cornea to generate particular optical power to correct refractive error. While the latter implant the customized lens which can provide larger range of myopia correction, especially for the extremely high myopic eyes that are unsuitable for laser refractive surgery due to corneal thickness. Although the efficacy, safety and predictability of all kinds of refractive surgery have been proved by years of clinical practice⁶, it is unavoidable to generate additional high-order aberration.⁷

Therefore, to provide evidence for individual choice of two main types of refractive surgery, researchers have devoted to exam the visual quality after different surgery. In case of laser refractive surgeries including ReLEx small-incision lenticule extraction (SMILE) photorefractive keratectomy (PRK) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK), the difference of postoperative visual quality was relatively moderate,⁸ since the optical irregularities of the eye were mostly caused by corneal laser wound healing progress.⁹But it is less reasonable to directly compare visual qualities between patients after laser refractive surgeries and ICL Implantation considering the operation indications of them are different. Laser refractive surgeries always performed in patients with low to moderate myopia due to the limitation of corneal condition, while the ICL Implantation can correct high myopia up to -20D. At the same time, the refractive err and corneal conditions have influence on visual quality. Comparing with emmetropic eyes, myopic eyes were reported that have higher corneal astigmatism, steeper corneal curvature and worse visual quality^10,11. To sum up, the inequality of baseline parameters is hard to avoid and would influence the measurement of visual quality.

In this study, we aim to explore the subjective and objective visual quality after laser refractive surgeries and ICL Implantation by inverse probability of treatment weighting (IPTW) analyses, which can reduce the impact of confounding factors effectively.

Study population

This retrospective study included 58eyes of 33 patients with myopia and myopic astigmatism who underwent ICL V4c implantation or laser refractive surgery (including SMILE and FS-LASIK) in our hospital between July 2022 to December 2021. The inclusion criteria:(1) age ≥ 20 years; (2) refractive error was stable (≤ 0.50 D change per year in refractive error) in the past 2 years); (3) for ICL implantation, the anterior chamber depth (ACD, measured from the endothelium) ≥ 2.8 mm and the endothelial cell density (ECD) ≥ 2500 cells/mm2; for SMILE and FS-LASIK, the calculated residual corneal stromal bed thickness ≥ 280 µm.

The exclusion criteria:(1) other pre-existing ocular diseases; (2) suspicion of keratectasia; (3) history of ocular trauma or surgery; (4) systemic diseases, such as hyperthyroidism and autoimmune diseases, or severe mental disorders, such as anxiety and depression. All patients had complete baseline clinical information and follow-up data. The current study was conducted in keeping with the principles of the Declaration of Helsinki and the ethical committee of the Zhongshan Ophthalmic Center, Sun Yat-sen University. Ethics number: 2023KYPJ287.

Surgical Protocol

The ICL V4c power calculation (STAAR Surgical, Nidau, Switzerland) was performed with the formula of ICL Power Calculation according to the white-to-white and the anterior chamber depth (ACD) measured by the Pentacam system (Oculus GmbH, Wetzlar, Germany). The axis for corneal astigmatism was marker before surgery. Sterile operation was performed during this surgery .The main 3.2 mm incision was made at the steepest meridian of the cornea ,then the ICL was injected into anterior chamber using manufacturer injector cartridge (STAAR Surgical Co.) after the viscoelastic material (SingcleanTM; Hangzhou Singclean Medicine Products Co ., Ltd; China) had been placed into the anterior chamber ,and moved to the posterior chamber through pupil .After correcting the position of lens, viscoelastic material was washed out using a balanced saline solution. Before surgery compound tropicamide eye drops (Zhuo bianTM;Shenyang Xing Qi Eye Drops Medicine Co., Ltd; China ) were used for mydriasis. After surgery, antibiotic (0.3% Ofloxacin ,TarividTM; Santen Pharmaceutic Co., Ltd ;China), drugs were applied topically 4 times a day for 4 weeks.

The VisuMax 500-kHz femtosecond laser (Carl Zeiss Meditec, Jena, Germany) was used for SMILE treatments and FS-LASIK ffap creations. In the SMILE procedure, the intended cap thickness was 110 µm, and the cap diameterranged from 7.0 to 7.7 mm. The lenticule diameter was programmed between 6.0 and 6.8 mm. A transition zone was set at 0.1 mm when correcting the cylinder. Surgical procedures were performed using a coaxially sighted corneal light reffex (CSCLR) centration method. A 2-mm incision was cut at the 130° position for subsequent lenticule dissection and extraction. After the scanning procedure, the lenticule was dissected and removed through the small incision, using a pair of spatulas. In the FS-LASIK procedure, the intended ffap thickness was 95 µm and the ffap diameter was varied from 8.1 to 8.5 mm with a superior hinge position. Surgical procedures were centered on the CSCLR with pupil tracking enabled. After the ffap was lifted, ablation of the stromal bed was performed using the AMARIS 750S excimer laser (Schwind eye-tech-solutions, Kleinostheim, Germany).The postoperative regimen included the administration of topical 0.5% levoffoxacin eyedrops (Tarivid; Santen Pharmaceutical, Osaka, Japan) and 0.25% tobramycin and dexamethasone eyedrops (Maxidex; Alcon Laboratories, Ft. Worth, TX) four times per day for 1 week. Subsequently, 0.1% fuorometholone eyedrops (Tarivid) were given four times per day for 3 weeks

Objective visual quality

Higher-order aberrations (HOAs) were measured using an OPD-Scan III aberrometer (Nidek Co., Ltd., Gamagori, Japan) for a 6-mm analytical zone up to the sixth order of Zernike polynomials preoperatively and 1 week postoperatively. The root mean square (RMS) value was used to analyze whole-eye total HOAs, coma, trefoil, and spherical aberrations. All measurements were taken under mesopic (3cd/m²) lighting conditions to avoid the influence of the pupil diameter. The patient was instructed to stare at the point light source from the equipment when we measured the parameters using the OPD-Scan III

Subjective visual quality

The subjective visual quality was obtained through the Quality of Vision (QoV) questionnaire developed by McAlinden et al.¹² encompasses 10 different categories of visual disturbance: glare, haloes, starbursts, hazy vision, blurred vision, distortion, double or multiple images, vision ffuctuation, focusing difffculty, and difffculty judging distance/depth perception. The questionnaire evaluated the patient’s QoV in terms of symptom frequency (never, 0; occasionally, 1; quite often, 2; very often, 3), severity (not at all, 0; mild, 1; moderate, 2; severe, 3), and bothersome (not at all, 0; a little, 1; quite, 2; very, 3). The patients were asked to complete QoV questionnaire before surgery and after one week of surgery.

Statistical Analysis

The propensity score inverse probability of treatment weighting (PS- IPTW) was used to balance the baseline characteristics between the laser refractive surgery group and ICL V4c implantation group. The propensity score (PS) for each patient was calculated as the predicted probability of being treated with ICL implantation using multivariable logistic regression. This model included the following variables including age, spherical refractive error, cylindrical refractive error, pupil diameter, flat corneal keratometry (K1) and steep corneal keratometry (K2). The variables chosen were based on a literature review, clinical experience, and theoretical considerations. The ICL V4c implantation group was weighted by 1/PS, whereas the laser refractive surgery group was weighted by 1/(1– PS). All analyses were performed using R statistical software (version 4.2.1). The R packages “Tableone”, “Survey” and “WeightIt” were used. Differences between two groups were tested with Student’s t-test. Less than 5% of the data were missing; these data were excluded from the statistical analysis. Statistical significance was set at p < 0.05.

Inverse probability of treatment weight outcomes

The propensity score (PS) for each patient was calculated as the predicted probability of being treated with ICL implantation using multivariable logistic regression. This model included the following variables including age, spherical refractive error, cylindrical refractive error, pupil diameter, flat corneal keratometry (K1) and steep corneal keratometry (K2). After IPTW, the confounding factors with statistical significance between laser refractive surgery group and ICL implantation group including spherical refractive error, cylindrical refractive error and K1 have been adjusted in Table1.

Table1.Baseline characteristics in the unweighted versus inverse probability of treatment weighting (IPTW)- weighted groups

	Unweighted			IPTW-weighted
	Laser refractive surgery	ICL implantation	P value	Laser refractive surgery	ICL implantation	P value
Age	25.05±5.30	26.21±5.31	0.432	48.74±35.07	62.25±115.83	0.614
Spherical refractive error	-5.56±2.46	-8.84±2.72	＜0.001	-12.13±12.87	-15.22±18.00	0.499
Cylindrical refractive error	-0.71±0.90	-1.72±1.37	0.001	-2.04±4.73	-2.29±1.63	0.770
Pupil diameter	6.33±0.82	6.64±1.01	0.255	11.93±7.22	14.74±26.33	0.642
K1	7.62±0.22	7.48±0.25	0.046	14.13±7.71	17.91±34.98	0.637
K2	7.86±0.27	7.88±0.38	0.880	14.66±8.21	18.60±36.10	0.633

Comparison of objective visual quality

Table2.Comparison of postoperative objective visual quality in the unweighted versus IPTW-weighted groups

	Unweighted			IPTW-weighted
	Laser refractive surgery	ICL implantation	P value	Laser refractive surgery	ICL implantation	P value
Total aberrevation	1.87±1.53	3.73±5.70	0.160	3.64±3.9	8.67±25.01	0.377
High order aberrevation	0.67±0.61	2.19±4.53	0.142	1.5±2.22	2.96±5.26	0.242
Coma aberration	0.42±0.48	1.11±1.42	0.008	0.84±1.44	1.45±1.63	0.166
Terafoil aberrevation	0.34±0.30	0.83±1.49	0.152	0.82±1.45	1.21±1.83	0.408
Spherical aberration	0.18±0.23	0.68±0.72	＜0.001	0.41±0.68	0.93±0.86	0.023
MTF	62.33±23.42	41.88±17.89	＜0.001	106.75±47.75	142.99±393.17	0.684
SR	0.04±0.03	0.02±0.02	0.004	0.07±0.05	0.09±0.35	0.747

Before IPTW, the objective visual quality of laser refractive surgery was better than ICL implantation based on the statistical significance in coma aberration (p＝0.008), spherical aberration (p<0.001), MTF(p<0.001) and SR(p＝0.004). However, after IPTW, only spherical aberration(p＝0.023) is statistically different between two groups showed in Table2.

Comparison of subjective visual quality (QoV scores)

To sum up, the patients who underwent laser refractive surgery reported better subjective visual quality in frequency(p＝0.020), severity(p＝0.043) and bothersome(p＝0.002). But two groups showed no significant difference after IPTW in Table3.The comparison of scores in particular symptoms are presented in Figure1, Figure2 and Figure3.

Table3.Comparison of postoperative subjective visual quality (QoV)scores in the unweighted versus IPTW-weighted groups

	Unweighted			IPTW-weighted
	Laser refractive surgery	ICL implantation	P value	Laser refractive surgery	ICL implantation	P value
Frequency	5.58±2.78	7.82±3.58	0.020	9.39±4.71	15.86±34.08	0.416
Severity	3.74±2.81	5.74±3.73	0.043	3.73±3.44	11.37±34.62	0.344
Bothersome	2.21±2.18	4.64±3.60	0.002	5.75±4.00	12.72±30.65	0.330

There are plenty of researches tried to investigate the visual quality of different refractive surgery. However few of them can avoid the insufficiency that the imbalance of baseline characteristics of patients could generate confounding effect on statistical analysis. Parameters such as keratometry values, spherical refractive error, cylindrical refractive error and pupil diameter are all reported to have impact on visual quality^13–15. For instance, patients with high myopia are more likely to choose ICL implantation rather than laser refractive surgery due to the limitation of corneal thickness. While high myopia eyes always bear worse visual quality before refractive surgery for their higher corneal astigmatism, steeper corneal curvature and harder visual experience in daily life^10,11, which was also observed in our study in Table 1.Therefore, it is reasonable to doubt that the poor objective and subjective visual quality is caused by confounding factor mentioned above instead of different kinds of surgery since it is also inappropriate to select patients before study to avoid confounding effects. In this study, we used IPTW to effectively adjust the imbalance of baseline characteristics in Table 1 and the comparison of unweight and weighted statistical analysis shows that the confounding characteristics actually have influence on results.

Some researches tried to avoid the confounding effect of different baseline characteristics by select patients with special standards, such as only including low myopia patients who underwent ICL implantation¹⁶ or high myopia patients who underwent laser refractive surgery¹⁷. However as they also stated in their research, the using patients that relatively rare and special in clinical practice is one of the shortage of their study. Therefore, the aim of our research is to provide a new approach to balance the confounding factors without select patients to compare the visual quality of two types of refractive surgery.

. For objective visual quality, the ICL implantation group shows worse coma aberration (p=pdisappear of statistical significance of these parameters (except spherical aberration(p༝0.023)) may suggested that the difference is caused by confounding factors. According to an experimental simulation study¹⁸, the ICL implantation may cause additional stray light and ghost images considering the ICL as an additional optical interface that might cause light transmissibility. Similarly with the other confounding factors, it affect the visual quality larger in higher the myopic eyes since the refractive power of ICL is higher. Zheng et al. investigated the impact of astigmatism on HOAs by only corrected the spherical component of refractive errors. This study reported that astigmatism is positively correlated with HOAs, also supported our results that after adjusting the astigmatism, the HOAs of patients underwent two types of surgery are relatively similar. On the other hand, Wei et al. found that ICL implantation had less increase of HOAs than SMILE, ¹⁹ also support that the higher HOAs are not generated by implantation itself. Therefore, it is credible to draw a conclusion that the worse visual quality after ICL implantation than laser refractive surgery is mainly due to the difference of baseline characteristics of patients.

For subjective visual quality, patients who implanted ICL had higher QoV scores in frequency, severity and bothersome, which coincide the consequence of objective visual quality. Previous researches also reported that the incidence of vision symptoms such as halos and glare after ICL implantation is higher than SMILE^20–22. It seems contrary to most current researches that found ICL implantation didn’t have more impact on objective visual quality such as HOAs. However, after ITPW, it shows no significant difference between two types of surgery in Fig. 1, Fig. 2 and Figuere3. In conclusion, the better subjective visual quality in laser refractive surgery could be influenced by imbalanced baseline characteristics for some of the symptoms have already exist in patients with high myopia.

There are still limitations in this research. First of all, the focus of this research is early postoperative stage visual quality, which reduce the scope of application of our conclusion. In addition, the sample size of this study is relatively small since the ITPW is an effective way to adjust baseline imbalance especially in huge volume of sample. Therefore, we are planning to conduct further research with more samples and longer follow-up times to verify current conclusion and enlighten studies in the future.

The subjective and objective visual quality of patients who underwent laser refractive surgery and ICL implantation are relatively similar in early postoperative stage. The better subjective and objective visual quality in laser refractive surgery than ICL implantation could be influenced by imbalanced baseline characteristics.

Ethics approval and consent to participate

This study was conducted in accordance with the principles of the Declaration of Helsinki and was approved by the Ethics Committee of the Zhongshan Ophthalmic Center Review Board. Ethics number: 2023KYPJ287. Written informed consent was obtained from all patients after the nature and possible consequences of the study were explained.

Consent for publication

Not applicable.

Declaration of interest

None of the authors has conflict of the interest with this topic. All the authors did not get any financial support from the company.

Funding

The project from the Natural Science Research Foundation of Guangdong Province of China (grant No. 2019A1515010940)

Author Contribution

JY and ZYZ wrote the main manuscript text. JY, ZYZ and HL participated in the design of the study. RZH and YTN collected the data. ZYZ and HL prepared figures.SZ and JY has given final approval of the version to be published. All authors reviewed and approved the final manuscript.

Acknowledgements

This study was supported by the Natural Science Research Foundation of Guangdong Province of China (grant No. 2019A1515010940) received by JY, the Natural Science Research Foundation of Guangdong Province of China (grant No. 2018A030313117) received by SZ and the Science and Technology Foundation of Guangzhou of China (grant NO. 202102010278) received by SZ.

Data availability statement

The data that support the findings of this study are available from the corresponding author, Jing Yang, upon reasonable request.

Vitale S, Sperduto RD, Ferris FL 3. Increased prevalence of myopia in the United States between 1971–1972 and 1999–2004. Arch Ophthalmol Dec. 2009;127(12):1632–9. 10.1001/archophthalmol.2009.303.
Fricke TR, Jong M, Naidoo KS, et al. Global prevalence of visual impairment associated with myopic macular degeneration and temporal trends from 2000 through 2050: systematic review, meta-analysis and modelling. Br J Ophthalmol Jul. 2018;102(7):855–62. 10.1136/bjophthalmol-2017-311266.
Zou M, Wang S, Chen A, et al. Prevalence of myopic macular degeneration worldwide: a systematic review and meta-analysis. Br J Ophthalmol Dec. 2020;104(12):1748–54. 10.1136/bjophthalmol-2019-315298.
Holden BA, Fricke TR, Wilson DA, et al. Global Prevalence of Myopia and High Myopia and Temporal Trends from 2000 through 2050. Ophthalmol May. 2016;123(5):1036–42. 10.1016/j.ophtha.2016.01.006.
Karimian F, Feizi S, Doozande A. Higher-order aberrations in myopic eyes. J Ophthalmic Vis Res Jan. 2010;5(1):3–9.
Chen X, Guo L, Han T, Wu L, Wang X, Zhou X. Contralateral eye comparison of the long-term visual quality and stability between implantable collamer lens and laser refractive surgery for myopia. Acta Ophthalmol May. 2019;97(3):e471–8. 10.1111/aos.13846.
Di Y, Cui G, Li Y, Luo Y. A meta-analysis of visual outcomes and optical quality after small incision lenticule extraction versus implantable collamer lens for myopia. Eur J Ophthalmol Jan. 2023;33(1):136–44. 10.1177/11206721221097249.
Sarkar S, Devi P, Vaddavalli PK, Reddy JC, Bharadwaj SR. Differences in Image Quality after Three Laser Keratorefractive Procedures for Myopia. Optom Vis Sci Feb. 2022;1(2):137–49. 10.1097/opx.0000000000001850.
Spadea L, Giammaria D, Trabucco P. Corneal wound healing after laser vision correction. Br J Ophthalmol Jan. 2016;100(1):28–33. 10.1136/bjophthalmol-2015-306770.
Khan MS, Humayun S, Fawad A, Ishaq M, Arzoo S, Mashhadi F. Comparison of higher order aberrations in patients with various refractive errors. Pak J Med Sci Jul-Aug. 2015;31(4):812–5. 10.12669/pjms.314.7538.
Paquin MP, Hamam H, Simonet P. Objective measurement of optical aberrations in myopic eyes. Optom Vis Sci May. 2002;79(5):285–91. 10.1097/00006324-200205000-00007.
McAlinden C, Pesudovs K, Moore JE. The development of an instrument to measure quality of vision: the Quality of Vision (QoV) questionnaire. Invest Ophthalmol Vis Sci Nov. 2010;51(11):5537–45. 10.1167/iovs.10-5341.
Ashena Z, Gallagher S, Naveed H, Spalton DJ, Nanavaty MA. Comparison of Anterior Corneal Aberrometry, Keratometry and Pupil Size with Scheimpflug Tomography and Ray Tracing Aberrometer. Vis (Basel) Mar. 2022;18(1). 10.3390/vision6010018.
Romashchenko D, Rosén R, Lundström L. Peripheral refraction and higher order aberrations. Clin Exp Optom Jan. 2020;103(1):86–94. 10.1111/cxo.12943.
Gomes J, Sapkota K, Franco S. Central and Peripheral Ocular High-Order Aberrations and Their Relationship with Accommodation and Refractive Error: A Review. Vis (Basel) Mar. 2023;7(1). 10.3390/vision7010019.
Fu M, Li M, Xian Y, et al. Two-Year Visual Outcomes of Evolution Implantable Collamer Lens and Small Incision Lenticule Extraction for the Correction of Low Myopia. Front Med (Lausanne). 2022;9:780000. 10.3389/fmed.2022.780000.
Chen D, Zhao X, Chou Y, Luo Y. Comparison of Visual Outcomes and Optical Quality of Femtosecond Laser-Assisted SMILE and Visian Implantable Collamer Lens (ICL V4c) Implantation for Moderate to High Myopia: A Meta-analysis. J Refract Surg Jun. 2022;38(6):332–8. 10.3928/1081597x-20220411-01.
Eppig T, Spira C, Tsintarakis T, et al. Ghost-image analysis in phakic intraocular lenses with central hole as a potential cause of dysphotopsia. J Cataract Refract Surg Nov. 2015;41(11):2552–9. 10.1016/j.jcrs.2015.05.034.
Wei R, Li M, Zhang H, et al. Comparison of objective and subjective visual quality early after implantable collamer lens V4c (ICL V4c) and small incision lenticule extraction (SMILE) for high myopia correction. Acta Ophthalmol Dec. 2020;98(8):e943–50. 10.1111/aos.14459.
Ieong A, Hau SC, Rubin GS, Allan BD. Quality of life in high myopia before and after implantable Collamer lens implantation. Ophthalmol Dec. 2010;117(12):2295–300. 10.1016/j.ophtha.2010.03.055.
Kamiya K, Igarashi A, Shimizu K, Matsumura K, Komatsu M. Visual performance after posterior chamber phakic intraocular lens implantation and wavefront-guided laser in situ keratomileusis for low to moderate myopia. Am J Ophthalmol Jun. 2012;153(6):1178–e861. 10.1016/j.ajo.2011.12.005.
Yu M, Chen M, Wang B, Zou L, Zhu X, Dai J. Comparison of Visual Quality After SMILE and LASEK for Mild to Moderate Myopia. J Refract Surg Dec. 2015;31(12):795–800. 10.3928/1081597x-20151111-02.

No competing interests reported.

Comparison of Subjective and Objective Visual Quality of Two Main Types of Refractive Surgeries in Early Postoperative Stage

Status:

Version 1

Abstract

Figures

Introduction

Materials and Methods

Study population

Surgical Protocol

Objective visual quality

Subjective visual quality

Statistical Analysis

Results

Discussion

Conclusion

Declarations