Mahmoud S Mady*, Ashraf A El-Shayeb, Hamdy A El-Gazzar, Mohamed G Masoud
Department of Ophthalmology, Faculty of Medicine, Banha University, Egypt
*Corresponding Author: Mahmoud S Mady, Mahmoud S Mady, Department of Ophthalmology, Faculty of Medicine, Banha University, Egypt.
Received: July 20, 2024; Published: August 23, 2024
Citation: Mahmoud S Mady., et al. “Evaluation of Outcomes of Surface Ablation Versus CIRCLE for Myopic Enhancement After SMILE". Acta Scientific Ophthalmology 7.9 (2024):11-18.
Background: In the treatment of myopia and myopic astigmatism, small incision lenticule extraction (SMILE) and fs-LASIK techniques have been established as equivalently safe and effective treatment options. Compared to surface ablation re-treatment after SMILE, CIRCLE procedure seems to offer advantages in respect to speed of visual recovery, safety, and predictability.
Aim: To compare the outcomes of enhancement after small incision lenticule extraction (SMILE) using surface ablation versus the CIRCLE procedure in patients with myopic and myopic astigmatism.
Methods: This is was a prospective, interventional comparative study conducted on 20 patients with myopia following SMILE operation. Cases were subdivided into two groups, group I included 10 cases who underwent CIRCLE operation and group II included 10 cases who underwent surface ablation. Refractive and functional outcomes were compared after a follow-up of six months.
Results: Regarding preoperative data, there were statistical significance difference between both groups in UCVA, BCVA, and cylinder, while regarding post-operative data, there were statistical significance differences between both groups regarding VA and sphere. Regarding comparison of outcomes, 100 % safety and efficacy were detected in both groups with no statistical significance while there was statistical significance difference between both groups regarding haze and pain .
Conclusion: This study showed that both surface ablation and CIRCLE procedures can be recommended as safe and effective re-treatment options for myopia after SMILE. The cap-to-flap procedure retreatment after SMILE procedure is a safe and efficacious treatment option for myopic patients.
Keywords: Small Incision Lenticule Extraction; Myopia; LASIK; CIRCLE; Surface Ablation
Transepithelial photorefractive keratectomy (Trans-PRK), laser-assisted in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) are three mainstay refractive surgeries worldwide. The applicability, efficacy, safety, and predictability of these different techniques are quite similar. Trans-PRK has the strongest biostability, earliest return to normal corneal sensitivity but the longest recovery time, most uncomfortable postoperative experience, and possibility of corneal haze. LASIK possesses the fastest visual rehabilitation but the slowest corneal nerve reinnervation, and flap displacement is possibly lifelong [1].
Since the introduction of the VisuMax femtosecond (FS) laser (Carl Zeiss Meditec, Jena, Germany) in 2007,8 small-incision lenticule extraction (SMILE) has been developed as a novel refractive surgery and is gaining popularity. Unlike traditional FS laser-assisted in situ keratomileusis (FS-LASIK), which requires 2 lasers, SMILE can be performed with a single FS laser platform, making it economically advantageous [2].
Both SMILE and WFG-LASIK are safe and effective ways to correct myopia and astigmatism. Compared with SMILE, WFG-LASIK has a lower surgical angle of error, higher surgical correction index of cylinder and induces less coma [3].
Although several studies have demonstrated that SMILE has achieved acceptable outcomes in correcting astigmatism,10,14 there remains a disagreement among surgeons regarding its application in correcting astigmatism because of the lack of automated cyclotorsion control and centration [4].
In the treatment of myopia and myopic astigmatism, small incision lenticule extraction (SMILE) and fs-LASIK have been established as equivalently safe and effective treatment options [5, 6]. In contrast to LASIK, which can be retreated by a flap re-SMILE retreatment is, however, currently neither approved nor commercially available in the Visu-Max platform , with sparse data on its safety and efficacy [7]. As a substitute, a multitude of alternative enhancement options have been proposed and established, including surface ablation, [8] cap-to-flap conversion using the CIRCLE program, [9] and thin-flap LASIK [10].
The CIRCLE procedure represents an effective re-treatment option after SMILE. Compared to surface ablation re-treatment after SMILE, CIRCLE seems to offer advantages in respect to speed of visual recovery, safety, and predictability, but at the price of flap creation [9]. To the best of our knowledge, there was only one research that directly comparing surface ablation versus CIRCLE enhancement after SMILE. They have demonstrated that both methods yielded comparable results in 3 months. However, CIRCLE re-treated eyes showed a markedly increased speed of recovery concerning UDVA and CDVA compared to surface ablation [11].
The present study was done to evaluate the safety and efficacy of myopic enhancement after small incision lenticule extraction using surface ablation versus the CIRCLE option.
This was a prospective, interventional comparative study conducted on a total of 20 patients with myopia following SMILE operation. Patients were collected from El-Nour Eye Center within the period from June 2022 to June 2023 after obtaining the approval from ethical Committee of Faculty of Medicine at Banha University. Cases were subdivided into two groups, group I included 10 cases who underwent CIRCLE operation and group II included 10 cases who underwent surface ablation.
This study included patients aged from 20 to 40 years old, both genders, normal fundus with myopia 0.5-6 diopters for more than 6 months after previous SMILE operation with stable refraction. Exclusuion cases were patients unfit for refractive surgery according to pentacam topography data such as corneal ectasia or inadequate corneal thickness, optical media opacity, ocular injuries, retinal or optic nerve pathology, diseases affecting visual pathway and patients who refused to participate in the study.
Every patient was subjected to full history including age, sex, and past history of medical or surgical problems. The ocular examination included assessment of BCVA by landolts broken ring chart and after that converted to log MAR, examination of anterior segment using slit lamp biomicroscopy (Haag streit BP 900), gonioscopy to examine anterior chamber angle, measurement of intraocular pressure by Goldman applanation tonometry, fundus examination using volk lens 90 diopters. Assessment of corneal topography and higher order aberrations using oculus pentacam (Oculus, Wetzlar, Germany).
Both eyes were anesthetized with few drops of topical anesthetic ( benoxinate 0.4) just before surgery. After the patient was positioned on the bed, an eyelid speculum was used to keep the eye open. The cone was connected to suction port. The patient's eye was positioned under the cone, and the patient was instructed to fixate on t he blinking green light. Suction was applied after centration on the visual axis. A VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) was used for the CIRCLE procedure.
The laser was initiated immediately after suction to create the flap. The procedure consisted of creating a junction cut to open a new treatment plane, creating a side cut with a hinge and then performing the excimer laser ablation [11]. A thin blunt spatula was inserted through the side cut to dissect and separate the flap. After lifting the flap, ablation was performed using the WaveLight Allegretto EX500 (Alcon Laboratories, Fort Worth, TX, USA) optical zone was set according to the mesopic pupil diameter and corrected diopters.
Under topical anesthesia an eyelid speculum was placed between the eyelids to keep them open and prevent blinking. The corneal epithelium was mechanically scraped using a blunt spatula. Ablation was applied using the WaveLight Allegretto EX500 (Alcon Laboratories, Fort Worth, TX, USA). Excimer laser was set for an optical zone of 6.5 mm and a transitional zone of 1.25 mm. After laser ablation, rinsing with 30 mL sterile balanced salt solution, a bandage contact lens was placed on the cornea.
At the end of the procedure, minimal washing of the interface with balanced salt solution was done for clearing of the Bowman's membrane folds that occured due to sudden collapse of anterior corneal layers and surgical manipulations [12].
Refractive and functional outcomes were compared after a follow-up of 1 month, then after 3 months then finaly after 6 months. Each visit included assessment of corrected and uncorrected visual acuity, anterior segment examination by slit lamp microscopy, refraction using autorefractometer, fundus biomicroscopy using Volk lens 90 diopters and corneal topography by oculus pentacam HR.
The collected data were coded, processed and analyzed using SPSS program (Statistical Package of Social Science, Version 16) for windows. The terms mean and SD were employed to represent quantitative values, while frequency and percentage were used to express categorical data. For the purpose of comparing parametric and non-parametric continuous data between groups, the independent sample T and Mann Whitney tests were employed, respectively. The cross-tabs function was utilized to compare nominal data between groups using the Fisher exact and Chi square tests. Based on the data type. P values less than 0.05 (5%) was considered statically significant.
Table (1) shows comparison of demographic and clinical data between studied groups, in which mean age in group 1 was 31.30 ± 5.87 however mean age in group 2 was 28.20 ± 3.26 without statistical significance difference between both groups. (p = 0.161). Regarding sex distribution in both groups, male represented 50 % in group 1 and 70 % in group 2 without statistical significance difference between both groups (P = 0.650). Right eye represented 70 % in group 1 and 100 % in group 2 without statistical significance difference between them (p = 0.211). Mean of Time after 1ry surgery in group 1 was 4.70 years ± 0.948 however, in group 2 was 3.60 years ± 0.97 with statistical significance difference between them (p = 0.019*).
There were statistical significance differences between both groups in UCVA, BCVA, cylinder (p = 0.04, 0.008, <0.001 repectively), however no statistical significance difference difference between both groups in sphere, SE (p = 0.418, 0.331 respectively).
Table (2) shows comparison of treatment parameters between studied groups in which there were statistical significance difference between both groups regarding Treatment time and residual stromal thinckness (RST) (p<0.001, 0.006 respectively). However, no statistical significance difference was detected regarding K reading, central corneal thickness (CCT) (p = 0.096, 0.429 respectively).
Table (3) shows comparison of post-operative data between studied groups in which there were statistical significance difference between both groups regarding VA, sphere (p = 0.001, 0.037 respectively). However no statistical significance was found regarding cyl (p = 0.093), mean value for SE in group 1 was -0.17 ± 0.58, however it was not applicable for group 2.
Regarding comparison of outcomes after 6 months follow up between studied groups, 100 % safety and 100 % efficacy was detected in both groups which no statistical significance was between the groups regarding safety and efficacy (p = 1,1 respectively). Regarding haze, 10% of the patients only in group 1, but 100 % of the patients in group 2 with statistical significance difference between both groups (p<0.001). There was quick recovery in all group 1 patients, in contrast 100 % of group 2 patients showed no quick recovery with statistical significance difference between both groups p<0.001*. Regarding pain, 100 % of group 1 patients had no pain in contrary to group 2 which suffered from pain by 100 % with statistical significance difference between both groups p<0.001*. There were no flap complications among both groups.
SMILE retreatment is performed when the refraction is overcorrected or undercorrected or optical regression has occurred. Because it is a relatively new surgery, data on the retreatment rates are limited [13]. A recent study showed the incidence of retreatment at 1 year and 2 years was 2.1% and 2.9%, respectively [14]. The reported range is from 1% to 4%. In comparison, retreatment rates for LASIK have usually ranged from 6% to 28% [15].
Surface ablation or photorefractive keratectomy (PRK) might be the simplest and most straightforward retreatment procedure after small incision lenticule extraction. Surface ablation is a safe and effective option [8]. In the context of surface ablation after myopic SMILE, Siedlecki., et al. [16] have displayed that; it could treat a residual spherical equivalent (SE) refraction of -0.86 ± 0.43 diopters (D) (range: -1.75 to 0.00 D) following SMILE by using surface ablation and mitomycin C (MMC), and obtained a mean residual SE of +0.03 ± 0.57 D 3 months after the enhancement. However, this residual SE ranged from -1.75 to +1.75 D, with 15% of patients showing more than +0.50 D of residual SE and 5% showing more than +1.00 D of SE.
A flap-conversion procedure, CIRCLE (Carl Zeiss Meditec AG), also known as cap-to-flap, is one of the newer retreatment modalities. It uses the Visumax femtosecond laser to create a side cut that converts the small-incision lenticule extraction cap into a LASIK flap. Retreatment using the cap-to-flap procedure has been found to be a safe and effective option, with slightly better visual outcomes than surface ablation [17].
The cap-to-flap procedure is becoming an increasingly popular. The software is simple to use, the flaps are reliable and can be easily lifted, and the procedure avoids the post-operative pain and delayed visual recovery that occur after surface ablation [18].
Therefore, the current study aimed to compare the outcomes of enhancement after SMILE using surface ablation versus the CIRCLE option, which converts the SMILE cap into a femtosecond laser-assisted laser in situ keratomileusis flap. The current study included 20 cases subdivided into two groups; Group I (n = 10): Cases underwent CIRCLE operation and Group II (n = 10): Cases underwent surface ablation. The current study showed that mean age in group 1 was 31.30 ± 5.87 versus mean age in group 2 was 28.20 ± 3.26 without statistical significance difference between both groups (p = 0.161). Regarding sex distribution in both groups, male represented 50 % in group 1 and 70 % in group 2 without statistical significance difference between both groups (P = 0.650).
The current study showed that there was statistical significance difference between both groups as regard preoperative data (UCVA, BCVA, cylinder) (p = 0.04, 0.008 and <0.001 respectively), however no statistical significance difference between both groups in sphere and SE (p = 0.418 and 0.331 respectively).
Siedlecki., et al. [19] showed that, in agreement with the present results, both groups did not differ before SMILE concerning age (P = 0.77). But in comparison to our results, they showed that there was also no difference concerning pre-enhancement MRSE (P = 0.97), spherical error (P = 1.00), astigmatism (P = 0.42), CDVA (P = 0.56), and UDVA (P = 0.11). Optical zone diameters and cap thickness values of the previous SMILE procedure were not different between groups (P = 0.19 and P = 0 .78).
Also, the current study showed that there was statistical significance difference between both groups regarding treatment time and RST (p<0.001 and 0.006 respectively). However, no statistical significance difference was detected regarding K reading and CCT (p = 0.096 and 0.429 respectively). The current study showed that there was statistical significance difference between both groups regarding post-operative data (VA and sphere) (p = 0.001 and 0.037 respectively), where values were higher in group 1. However no statistical significance was found regarding cyl (p = 0.093). Mean value for SE in group 1 was -0.17 ± 0.58, however it was not applicable for group 2.
In comparison to our findings, Siedlecki., et al. [19] found that UDVA improvement was similar to a final value of 0.02 ± 0.10 (surface ablation) versus 0.03 ± 0.07 (CIRCLE) logMAR (P = 0.78). Only one eye in the surface ablation group and no eye in the CIRCLE group lost one line of CDVA. Interestingly, the current study showed that 100 % safety and efficacy was detected in both groups which no statistical significance between the groups (p = 1and 1 respectively). Regarding haze, 10% of the patients only in group 1, but 100 % of the patients in group 2 with statistical significance difference between both groups (p<0.001). There was quick recovery in all group 1 patients, in contrast 100 % of group 2 patients showed no quick recovery with statistical significance difference between both groups (p<0.001*). Regarding pain, 100 % of group 1 patients had no pain in contrary to group 2 who suffered from pain by 100 % with statistical significance difference between both groups (p<0.001*).
In the matched comparative study by Siedlecki., et al. [19] CIRCLE and surface ablation yielded equivalent results at 3 months concerning target accuracy (100% within 0.50 D of target in both groups) and visual acuity (83% of eyes with 20/20 UDVA or better in both groups), resulting in equivalent safety (1.06 vs 1.00) and efficacy indices (1.03 vs 0.95).
Although neither procedure has been reported to cause significant loss of CDVA, CIRCLE seems to convey lower risk of losing ≥1 lines of CDVA [9]. The largest clinical difference between both options as perceivable by patients lies within the aspect of pain and speed of visual recovery. In this respect, CIRCLE represents a major improvement to surface ablation. In the matched comparative study, CIRCLE was superior to surface ablation concerning UDVA (approximately 2 lines) and CDVA (1 line) at week 1 after enhancement [20].
Also, in harmony with our results, it was reported that Surface ablation can cause significant inflammation and postoperative haze. Typically, there is greater recruitment of CD11b (a marker of inflammation) and terminal uridine deoxynucleotidyl nick end-labeling-positive cells (a marker of apoptosis) in the superficial layers of the corneal stroma than in other retreatment procedures [21].
CIRCLE software, originally indicated as a tool for enhancement after SMILE, allows conversion of SMILE cap into a flap, thus providing access to the interface [19]. Ganesh., et al. [22] and Reinstein., et al. [23] have demonstrated the use of CIRCLE software for the management of complicated lenticule dissection during SMILE surgery. Retreatment using the cap-to-flap procedure has been found to be a safe and effective option, with slightly better visual outcomes than surface ablation [17]. The cap-to-flap procedure is becoming an increasingly popular. The software is simple to use, the flaps are reliable and can be easily lifted, and the procedure avoids the post-operative pain and delayed visual recovery that occur after surface ablation. A drawback of the flap-conversion procedure is biomechanical weakening of the cornea caused by damage to Bowman layer and the anterior corneal cap [24].
The limitations of our study include a small sample size and short follow-up. Moreover, the use of different surface ablation profiles on two different excimer laser platforms (for surface ablation and for CIRCLE) should be considered.
The cap-to-flap procedure retreatment after small-incision lenticule extraction procedure is a safe and efficacious treatment option for patients who were undercorrected or overcorrected or who had optical regression. Compared with surface ablation, the cap-to-flap procedure appears to yield better visual outcomes and safety as well as accelerated visual recovery. Thus, this technique might appeal to patients who are not adverse to having a flap-related procedure.
None.
For this review, no financial sources were utilized.
None.
No financial relationship or connection with any entity or group that has a financial competing in the materials or subject matter under consideration.
None.
Entire data generated throughout this review are comprised in the study.
CONSORT guidelines were followed.
The initial draft of the manuscript had been written by the authors after they had evaluated and discussed the data.
The authors thank Dr. Ahmed A. Ghanem and Mr. Taha Baker for their care and diligence during revision and writing the paper.
Copyright: © 2024 Mahmoud S Mady., et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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