Surgical Technique to Treat Presbyopic Inlay-Associated Corneal Haze With Sequential Excimer Photoablation: A Case Series

PURPOSE

To describe an approach using sequential excimer laser ablation of the stromal surface of the corneal flap with or without subsequent excimer ablation to the stromal bed to reduce presbyopic inlay-associated corneal haze.

METHODS

Twelve patients who underwent KAMRA inlay (Acufocus) explantation due to corneal haze were included. The mean interval between explantation and the primary surgery (phototherapeutic keratotomy [PTK] to corneal flap) was 16.2 ± 29.7 months (range = 1 to 83 months). The corneal flap was lifted and laid on an evisceration spoon and an excimer laser was used to ablate the flap stroma by 30 to 40 µm depth. Subsequently, an excimer laser was used to ablate and treat the stromal bed following a second flap lift according to the manifest refraction, leaving a minimal residual stromal bed thickness of greater than 300 µm. For both procedures, mitomycin C 0.02% was applied to the stromal bed before the flap was replaced and a bandage contact lens applied.

RESULTS

Reductions in corneal haze were observed, following PTK to the corneal flap with or without photorefractive keratectomy (PRK) to the stromal bed, both clinically and on imaging. No significant changes in uncorrected distance visual acuity (P = .442) and corrected distance visual acuity (P = .565) were observed. Improvements were observed for both spherical equivalent refractive errors (P = .036) and corneal light backscatter (P = .019). There were significant improvements in spherical aberrations (P = .014) but no changes in total lower and higher order aberrations.

CONCLUSIONS

PTK to the corneal flap with or without subsequent stromal bed PRK is an effective technique in treating corneal haze following presbyopic inlay explantation. [J Refract Surg. 2023;39(9):639-646.].

CIRCLE Software for Management of Epithelial Ingrowth After SMILE

PURPOSE

To report a novel therapeutic use of CIRCLE software (Carl Zeiss Meditec) to manage visually significant epithelial ingrowth following small incision lenticule extraction surgery (SMILE).

METHODS

Case series.

RESULTS

In this case series, the authors describe three eyes with progressive and visually significant epithelial ingrowth following an uneventful SMILE procedure. The management of epithelial ingrowth following SMILE is challenging, given the small access incision to the interface and the risk of incomplete removal. All cases were successfully managed by converting the SMILE cap into a flap using the CIRCLE software, which provided the necessary access to the original SMILE interface. Once the flap was lifted, the epithelial in-growth was completely debrided from the underlying stroma and undersurface of the flap, followed by a thorough interface wash. Postoperative recovery was uneventful, with no recurrence noted in any of the eyes.

CONCLUSIONS

Use of CIRCLE software provides a novel and unique approach to successfully treating vision-threatening epithelial ingrowth after SMILE. [J Refract Surg. 2021;37(11):776-780.].

Decade - long journey with small incision lenticule extraction: The learnings

Over the past decade, small incision lenticule extraction (SMILE) has revolutionized the field of keratorefractive surgery. With the promise of superior corneal biomechanics and reduced postoperative dry eye, SMILE afforded a distinct advantage over flap-based procedures. Our evolving understanding of the surgical technique and management of its unique complications has further enhanced the outcomes. This review will highlight specific pearls on various preoperative and intraoperative principles allowing optimization of outcomes with SMILE.

Complications of small incision lenticule extraction

The procedure of small incision lenticule extraction (SMILE) was introduced in 2011, and since then there has been an increase in the number of cases undergoing this procedure worldwide. The surgery has a learning curve and may be associated with problems in the intraoperative and postoperative periods. The intraoperative problems during SMILE surgery include the loss of suction, the occurrence of altered or irregular opaque bubble layer and black spots, difficulty in lenticular dissection and extraction, cap perforation, incision-related problems, and decentered ablation. Most of the postoperative problems are similar as in other laser refractive procedures, but with decreased incidence. The identification of risk factors, clinical features, and management of complications of SMILE help to obtain optimum refractive outcomes.

A comparison of the effects of different cap thicknesses on corneal nerve destruction after small incision lenticule extraction

OBJECTIVE

To evaluate the features of corneal nerve destruction after small incision lenticule extraction (SMILE) with different cap thicknesses (100 and 120 μm).

METHODS

Nine consecutive patients (18 eyes) received SMILE with a 120-μm cap thickness and nine patients (18 eyes) with a 100-μm cap thickness were recruited. Confocal microscopy was used to evaluate the density and microscopic morphological changes of central corneal subbasal nerves preoperatively and at postoperative week 1.

RESULTS

The postoperative corneal subbasal nerve densities decreased significantly in both 120 μm and 100 μm groups. No statistical difference was detected in reduction of subbasal nerve density between two groups (P = 0.299). The number of subbasal nerve fibers significantly decreased in both groups. The reductions were not significantly different between two groups (P = 0.293).

CONCLUSIONS

Using a 120-μm cap thickness during SMILE preserves no more central corneal subbasal nerve fibers compared to a 100-μm cap thickness.

Surgical options for retreatment after small-incision lenticule extraction: Advantages and disadvantages

Since the inception of small-incision lenticule extraction (SMILE), many surgeons have speculated the lack of an adequate and standard retreatment procedure will impede its popularity. However, more than 1 million patients worldwide have had this surgery, with visual outcomes nearly equivalent to current laser in situ keratomileusis (LASIK) results. With the procedure's growing popularity, some patients will inevitably have a postoperative residual refractive error from regression, overcorrection, undercorrection, and astigmatic induction and will require retreatment. To our knowledge, literature reviewing major retreatment options is limited. Options include surface ablation, thin-flap LASIK, secondary small-incision lenticule extraction, and a cap-to-flap procedure (CIRCLE) in which a femtosecond laser is use to create cuts that convert the small-incision lenticule extraction cap into a LASIK flap. This review discusses major advantages and disadvantages of these options and compares the visual outcomes based on the existing literature. An algorithmic approach created from this analysis is presented to guide retreatment decision-making.

Refractive surprise: twice the SMILE

A 35-year-old man presented with decreased vision in his left eye following small incision lenticule extraction (SMILE) surgery. The refractive error after surgery was nearly twice his preoperative refractive error in the left eye. The patient was diagnosed as having a retained lenticule after SMILE surgery, which was folded on itself and was successfully managed by conversion to a flap. Postoperatively, the patient maintained good uncorrected visual acuity and a low refractive error, with the best spectacle corrected acuity of 20/20.

Future Developments in SMILE: Higher Degree of Myopia and Hyperopia

Small incision lenticule extraction (SMILE) is a novel 1-step refractive procedure with femtosecond laser for the correction of myopia and myopic astigmatism. Although it has shown good clinical results in efficacy, safety, predictability, and stability, there are still some concerns. In this study, we review the published clinical outcomes of high myopia correction and exploration in hyperopia correction. Results have suggested that SMILE has acceptable outcomes in correction for high myopia <10.0 diopters (D), and it is a feasible and effective procedure for the treatment of hyperopia. However, it is unsuitable for the treatment of extremely high myopia because there is undercorrection and regression as existed in laser-assisted in situ keratomileusis (LASIK), and compound hyperopic astigmatism currently could not be corrected either. More technical and clinical improvements are required to make SMILE competitive.

Enhancement Options After Myopic Small-Incision Lenticule Extraction (SMILE): A Review

PURPOSE

To provide an overview of the currently available retreatment methods after myopic small-incision lenticule extraction (SMILE).

DESIGN

Systematic literature review.

METHODS

The PubMed library was searched for articles containing the terms "small-incision lenticule extraction" and "enhancement" or "retreatment". The last search was performed on May 1, 2019.

RESULTS

In contrast to laser in-situ keratomileusis (LASIK), which can be retreated by a flap relift, repeat SMILE retreatment is currently not approved and only seldomly performed. As substitutes, surface ablation, cap-to-flap conversion using the CIRCLE program in the VisuMax platform, and thin-flap LASIK have been recently established. While all options offer safety and efficacy comparable to LASIK retreatments, each has its patient-specific advantages and disadvantages. While surface ablation preserves the flap-free approach of the primary procedure, the aspect of pain and a slow visual recovery might render it less attractive as compared with CIRCLE and thin-flap LASIK which offer quick recovery, however at the price of flap creation. Besides, each retreatment method generates specific tissue responses and has a different impact on corneal biomechanics, which is strongly dependent on the previous SMILE parameters, especially the cap thickness.

CONCLUSIONS

Refractive enhancement after SMILE is currently mostly performed by surface ablation, CIRCLE cap-to-flap conversion or thin-flap LASIK, which all offer safety and efficacy comparable to LASIK retreatments. In this review, a detailed overview over each method, its technical aspects, and specific advantages and disadvantages is given.

Surface Ablation Versus CIRCLE for Myopic Enhancement After SMILE: A Matched Comparative Study

PURPOSE

To compare the outcomes of enhancement after small incision lenticule extraction (SMILE) using surface ablation versus the VisuMax CIRCLE option (Carl Zeiss Meditec AG, Jena, Germany), which converts the SMILE cap into a femtosecond laser-assisted laser in situ keratomileusis flap.

METHODS

The databases of the SMILE Eyes centers in Munich, Marburg, and Cologne, Germany, and Linz, Austria, were screened for eyes that had undergone enhancement using surface ablation with mitomycin C or CIRCLE. Eyes from both enhancement methods suitable for a retrospective matched analysis were identified based on pre-SMILE and pre-enhancement mean refractive spherical equivalent (MRSE), astigmatism, age, and corrected and uncorrected distance visual acuity (CDVA/UDVA). Refractive and functional outcomes were compared after a follow-up of 3 months.

RESULTS

After the application of the matching criteria on 2,803 SMILE procedures, 24 eyes (12 in each group) with a follow-up of 3 months or longer were available for analysis. Enhancement was performed after a mean 9.7 ± 7.2 (surface ablation) and 11.0 ± 4.4 (CIRCLE) months for a residual MRSE of -0.91 ± 0.55 (surface ablation) and -0.90 ± 0.61 (CIRCLE) diopters. At 3 months, residual MRSE showed comparable accuracy with -0.07 ± 0.19 (surface ablation) and 0.04 ± 0.22 (CIRCLE) diopters (P = .18). UDVA improvement was similar to a final value of 0.02 ± 0.10 (surface ablation) versus 0.03 ± 0.07 (CIRCLE) logMAR (P = .78). Only one eye in the surface ablation group and no eye in the CIRCLE group lost one line of CDVA. At 3 months, the safety (surface ablation: 1.00, CIRCLE: 1.06; P = .36) and efficacy (surface ablation: 0.95, CIRCLE: 1.03; P = .36) indices were equivalent. In terms of speed of visual recovery, at week 1 UDVA and CDVA were significantly better after CIRCLE than surface ablation (P = .008 and .002, respectively).

CONCLUSIONS

In this first study directly comparing surface ablation versus CIRCLE enhancement after SMILE, both methods yielded comparable results at 3 months. However, CIRCLE re-treated eyes showed a markedly increased speed of recovery concerning UDVA and CDVA compared to surface ablation. [J Refract Surg. 2019;35(5):294-300.].

Aborted small-incision lenticule extraction resulting from false plane creation and strategy for subsequent removal based on corneal layered pachymetry imaging

We describe a complication of false plane creation during small-incision lenticule extraction (SMILE) and the surgical plan for subsequent lenticule removal. During a primary SMILE procedure to treat high myopia, the separator instrument entered a false lamellar plane as a result of an area of resistance caused by an area of opaque bubble layer (OBL). The procedure was aborted to avoid removing an irregular lenticule. Based on measurements of the anatomic landscape, a new inferonasal small incision was created. The lenticule was separated and removed without further incidence. The patient recovered as normal and at 6 months, the uncorrected distance visual acuity was 20/16^-1. This case highlights the importance of monitoring the bubble layer creation and interface separation to avoid creating or removing an irregular lenticule. It also shows the importance of layered corneal imaging to analyze and diagnose complications as well as of aborting a procedure and planning lenticule removal at a later time if deemed appropriate.

Comparison of visual quality after EVO-ICL implantation and SMILE to select the appropriate surgical method for high myopia

Background

This study sought to compare the visual quality between intraocular collamer lens (EVO-ICL) implantation and small-incision lenticule extraction (SMILE) and determine the appropriate surgical method to treat patients with high myopia (− 6.25 to − 10 D).

Methods

A total of 48 eyes underwent EVO-ICL implantation and another 48 eyes underwent SMILE. The uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (BCVA) and equivalent spherical degree were compared across the SMILE (− 6.25 to − 10 D) and EVO-ICL (− 6.25 to − 10 D) implantation groups. Preoperative and postoperative visual quality parameters were compared between and within groups.

Results

The OQAS II values (OV 100%) one week and one month after surgery and the modulation transfer function (MTF), OV 20% and OV 9% values one week after surgery in the SMILE group were lower than the respective preoperative values. The objective scatter index (OSI) value increased one week as well as one month after surgery compared with the preoperative values. The MTF cut-off value of the SMILE group was lower than that of the EVO-ICL implantation group three months after surgery.

Conclusions

For patients with high myopia, the postoperative visual quality of EVO- ICL implantation was slightly better than that of SMILE.

CIRCLE Software for the Management of Retained Lenticule Tissue Following Complicated SMILE Surgery

PURPOSE

To describe the therapeutic use of CIRCLE software (Carl Zeiss Meditec, Jena, Germany) for the management of retained lenticule tissue after complicated small incision lenticule extraction (SMILE).

METHODS

Two patients were referred for consultation and treatment due to intraoperative complications during SMILE. In case 1, a black patch during laser delivery caused the lenticule to be torn irregularly from the undersurface during extraction and a sliver of it was retained in the pocket. Case 2 presented with false plane dissection and a completely retained lenticule on anterior segment optical coherence tomography. Both cases were managed using the CIRCLE software by converting the cap into a flap, thus making access to the interface possible.

RESULTS

In case 1, after lifting the flap a small sliver of tissue was found in the interface, which was dissected, following which a 20-µm phototherapeutic keratectomy was done to smooth the interface. In case 2, after lifting the flap the edge of the retained lenticule was identified by using an endoilluminator and the lenticule was separated and subsequently removed. Both cases showed significant improvement in uncorrected distance visual acuity, corrected distance visual acuity, and Objective Scatter Index score on day 1 after repair surgery.

CONCLUSIONS

CIRCLE software may be successfully used for managing retained lenticule tissue apart from performing enhancement after SMILE. [J Refract Surg. 2019;35(1):60-65.].

Outcomes of Re-treatment by LASIK After SMILE

PURPOSE

To report the outcomes of LASIK re-treatments after small incision lenticule extraction (SMILE).

METHODS

Retrospective review of all eyes to have undergone a re-treatment by LASIK after primary SMILE between September 2013 and January 2016. Thin-flap LASIK was used in most cases as long as sufficient tissue was available for safe flap creation between the maximum epithelial thickness and minimum cap thickness. Otherwise, the SMILE interface was converted into a LASIK flap by the Circle technique or side cut only. The multivariate nomogram for LASIK re-treatments was used, including sphere, cylinder, age, and primary spherical equivalent (SEQ) as variables. Patients were observed for 1 year after surgery and standard outcomes analysis was performed.

RESULTS

A total of 116 LASIK re-treatments were performed in a population of 2,643 consecutive SMILE procedures, indicating a re-treatment rate of 4.39%. Mean attempted SEQ was -0.05 ± 0.99 diopters (D) (range: -1.88 to +1.50 D). Mean cylinder was -0.70 ± 0.55 D (range: 0.00 to -2.25 D). Postoperative uncorrected distance visual acuity was 20/20 or better in 81% of eyes, for a population with corrected distance visual acuity (CDVA) of 20/20 or better in 95% before re-treatment. Mean postoperative SEQ relative to the target was +0.19 ± 0.49 D (range: -0.88 to +2.13 D), with 74% within ±0.50 D. Mean postoperative cylinder was -0.29 ± 0.24 D (range: 0.00 to -1.25 D). There was one line loss of CDVA in 15% of eyes, but no eyes lost two or more lines. There was a small increase in contrast sensitivity (P < .05). Overcorrection was identified in myopic re-treatments (n = 20) of -1.00 D or more; mean postoperative SEQ was +0.59 ± 0.64 D (range: -0.63 to +2.13 D).

CONCLUSIONS

Re-treatment after SMILE by LASIK achieved excellent visual and refractive outcomes, although these results indicate that myopic LASIK retreatment after primary myopic SMILE requires a different nomogram than for myopic LASIK re-treatment after primary myopic LASIK. [J Refract Surg. 2018;34(9):578-588.].

Inferior pseudo-hinge fulcrum technique and intraoperative complications of laser in situ keratomileusis retreatment after small-incision lenticule extraction

PURPOSE

To describe the evolution of a flap-lift technique for laser in situ keratomileusis (LASIK) retreatment after small-incision lenticule extraction (SMILE) and report the incidence of complications.

SETTING

London Vision Clinic, London, United Kingdom.

DESIGN

Retrospective case series.

METHODS

All retreatments between September 2013 and January 2017 were included. A bimanual inferior pseudo-hinge fulcrum flap-lift technique was developed to minimize the chance of tearing or entering the small incision. A flap lifter and a McPherson forceps were inserted into the inferior one third of the flap, slightly angled up to avoid perforating the small-incision lenticule extraction interface. One instrument provided countertraction, and the second separated the interface superiorly, keeping the tip away from the incision. One instrument was held against the hinge for the second instrument to separate the inferior one third. The incidence of intraoperative complications was analyzed.

RESULTS

The study evaluated 162 retreatments (4.12%) for 3933 small-incision lenticule extraction treatments (1-year maturity). The retreatment was LASIK (n = 135), side-cut only (n = 1), cap-to-flap procedure (CIRCLE) (n = 3), or photorefractive keratectomy (n = 23). Two eyes (1.4%) had a tear to the small incision. The small-incision lenticule extraction interface was accessed in 8 eyes (5.8%), 1 (0.7%) centrally, and the interface was lifted in 1 eye (0.7%). There were no complications in the last 84 consecutive procedures (60%) using the finalized technique.

CONCLUSION

The bimanual inferior pseudo-hinge fulcrum decreased the risk for accessing the small-incision lenticule extraction interface or tearing the small incision.

Small incision lenticule extraction (SMILE) techniques: patient selection and perspectives

Refractive lenticule extraction is becoming the procedure of choice for the management of myopia and myopic astigmatism owing to its precision, biomechanical stability, and better ocular surface. It has similar safety, efficacy, and predictability as femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and is associated with better patient satisfaction. The conventional technique of small incision lenticule extraction (SMILE) involves docking, femtosecond laser application, lenticule dissection from the surrounding stroma, and extraction. It has a steep learning curve compared to conventional flap-based corneal ablative procedures, and the surgical technique may be challenging especially for a novice surgeon. As SMILE is gaining worldwide acceptance among refractive surgeons, different modifications of the surgical technique have been described to ease the process of lenticule extraction and minimize complications. Good patient selection is essential to ensure optimal patient satisfaction, and novice surgeons should avoid cases with low myopia (thin refractive lenticules), difficult orbital anatomy, high astigmatism, or uncooperative, anxious patients to minimize complications. A comprehensive MEDLINE search was performed using “small incision lenticule extraction,” “SMILE,” and “refractive lenticule extraction” as keywords, and we herein review the patient selection for SMILE and various surgical techniques of SMILE with their pros and cons. With increasing surgeon experience, a standard technique is expected to evolve that may be performed in all types of cases with optimal outcomes and minimal adverse effects.

[SMILE (Small Incision Lenticule Extraction) among the corneal refractive surgeries in 2018 (French translation of the article)]

Refractive surgery is a field in constant evolution. In recent years, a new procedure has appeared under the name SMILE (Small Incision Lenticule Extraction). This technique, carried out solely with a femtosecond laser, should make it possible to better preserve corneal innervation and biomechanics. After a detailed review of the technique itself, we then focus on the scientific evidence for the safety and efficacy of SMILE and its current indications. Advantages of SMILE will be discussed in comparison to disadvantages of the conventional techniques, particularly concerning dry eye and the risk of corneal ectasia with LASIK. Lastly, the current limitations of SMILE (indications, retreatment) are discussed, and future applications are considered regarding improvements in the technique.

CIRCLE Enhancement After Myopic SMILE

PURPOSE

To report the outcomes of enhancement after small incision lenticule extraction (SMILE) using the VisuMax CIRCLE option (Carl Zeiss Meditec AG, Jena, Germany), which converts the SMILE cap into a femtosecond LASIK flap for secondary excimer laser application.

METHODS

Of 2,065 SMILE procedures, 22 eyes (1.1%) re-treated with CIRCLE with a follow-up of 3 months were included in the analysis. SMILE was performed in the usual manner. For re-treatment, the CIRCLE procedure was performed with pattern D flap creation on the VisuMax system and subsequent excimer laser ablation with a Zeiss MEL 90 laser (Carl Zeiss Meditec) with plano target in all cases.

RESULTS

Spherical equivalent was -5.56 ± 2.22 diopters (D) before SMILE and -0.51 ± 1.08 D before CIRCLE. CIRCLE enhancement was performed after a mean of 10.0 ± 7.9 months, allowed for safe flap lifting in all eyes, and resulted in a final manifest refraction spherical equivalent of 0.18 ± 0.31 D at 3 months (P < .008). The number of eyes within 0.50 and 1.00 D from target refraction increased from 31.8% to 90.9% and from 77.3% to 100%, respectively. Mean uncorrected distance visual acuity (UDVA) had already improved from 0.37 ± 0.16 to 0.08 ± 0.16 logMAR at 1 week (P < .0001), resulting in 0.03 ± 0.07 logMAR at 3 months (P < .0001). All eyes gained at least one line of UDVA. Corrected distance visual acuity (CDVA) remained unchanged at all time points (before vs after CIRCLE, P = .40). Two eyes (9.1 %) lost one line of CDVA; no eye lost two or more lines. The safety and efficacy indices were 1.03 and 0.97 at 3 months.

CONCLUSIONS

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. [J Refract Surg. 2018;34(5):304-309.].

SMILE (Small Incision Lenticule Extraction) among the corneal refractive surgeries in 2018

Refractive surgery is a field in constant evolution. In recent years, a new procedure has appeared under the name SMILE (SMall Incision Lenticule Extraction). This technique, carried out solely with a femtosecond laser, should make it possible to better preserve corneal innervation and biomechanics. After a detailed review of the technique itself, we then focus on the scientific evidence for the safety and efficacy of SMILE and its current indications. Advantages of SMILE will be discussed in comparison to the conventional techniques, particularly concerning dry eye and the risk of corneal ectasia related to LASIK. Lastly, the current limitations of SMILE (indications, retreatment) are discussed, and future applications are considered regarding new improvements in the technique.

Refractive lenticule extraction small incision lenticule extraction: A new refractive surgery paradigm

Small incision lenticule extraction (SMILE), a variant of refractive lenticule extraction technology is becoming increasingly popular, as a flapless and minimally invasive form of laser vision correction (LVC) for the treatment of myopia and myopic astigmatism. This review aims at summarizing the principles, surgical technique, and clinical outcomes in terms of visual and refractive results, safety, efficacy, postoperative dry eye, aberrations, and biomechanics of SMILE and its comparison with other conventional techniques of LVC, such as laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). Recent advancements in the laser frequency and energy delivery patterns, instrumentation, and surgical techniques have shown significant improvement in the visual recovery and outcomes after SMILE, compared to the initial results published by Sekundo and Shah et al. Most of the recently published literature on long-term outcomes of SMILE shows excellent stability of the procedure, especially for higher myopia. In terms of the postoperative dry eye, SMILE shows a clear advantage over LASIK as numerous studies have shown significant differences about the Schirmer's, Tear film break up time, corneal sensitivity, and corneal nerve regeneration to be better following SMILE compared to LASIK. There is some evidence that since the Bowman's membrane (BM) and the anterior lamellae remain intact after SMILE, this may be a potential advantage for corneal biomechanics over LASIK and PRK where the BM is either severed or ablated, respectively, however, the data on biomechanics are inconclusive at present. Overall, this procedure has proved to be promising, delivering equivalent, or better visual and refractive results to LASIK and providing clear advantage in terms of being a flapless, minimally invasive procedure with minimal pain and postoperative discomfort thus offering high patient satisfaction.

Cap-preserving SMILE Enhancement Surgery

BACKGROUND

Different enhancement procedures have been suggested for reduction of residual refractive errors after SMILE. The aim of this study is to evaluate an improved cap-preserving technique for enhancement after SMILE (Re-SMILE).

METHODS

A retrospective case series was conducted at Eye subspecialty center, Cairo, Egypt on 9 eyes with myopia or myopic astigmatism (spherical equivalent - 8.0 and - 12.0D). undergoing SMILE procedure and needed second interference. This was either because the more myopic meridian was more than - 10.0 D and therefore planned to have two-steps procedure (six eyes) or because of under correction needing enhancement (three eyes). Assessment after the primary SMILE procedure was conducted at 1 day, 1 week, 1 month and 3 months postoperatively. Assessment after Re-SMILE was conducted at 1 day, 1 week, 1 month, 3 months, 6 months and 1 year postoperatively. The assessments included full ophthalmic examination, objective and subjective refraction, and rotating Scheimpflug camera imaging.

RESULTS

Preoperatively, the mean refractive spherical equivalent (MRSE) values were: - 9.36 ± 0. 89. After primary SMILE it was - 2.18 ± 0.71. After Re-SMILE it was - 0.13 ± 0.68. MRSE was significantly improved after both procedures (P < 0.01). The safety index of primary SMILE cases was 1.65 ± 0.62 and for Re-SMILE 1.13 ± 0.34 and the efficacy index was 1.14 ± 0.24 after primary SMILE and 1.11 ± 0.26 after Re-SMILE.

CONCLUSION

Centered cap-preserving Re-SMILE is an effective procedure in reducing residual refractive errors after primary SMILE in high myopes.

Retreatment strategies following Small Incision Lenticule Extraction (SMILE): In vivo tissue responses

With any refractive correction, including Small Incision Lenticule Extraction (SMILE), there may be a residual refractive error that requires a retreatment. Here, we investigated the tissue responses following various retreatment procedures in a rabbit model of SMILE. All rabbits underwent a -6.00D correction with SMILE. Two weeks later, they underwent -1.00D enhancement by: (i) VisuMax Circle, followed by excimer ablation (S+C); (ii) secondary SMILE anterior to the primary procedure (S+SE); or (iii) surface ablation (S+P), and were examined for 28 days. S+P induced corneal edema and haze, and more CD11b- (23±6 cells) and TUNEL-positive (36±4 cells) cells in the central stromal superficial layers early post-operatively (p<0.001 compared to other procedures). The corneas appeared normal on day 28 after S+P, but had a lower number of keratocytes near the laser ablated plane compared to other procedures. S+SE and S+C did not induce corneal haze and resulted similar level of fibronectin. However, S+C resulted in more inflammatory (10±2 cells; p = 0.001) and apoptotic cells (25±2 cells; p<0.001) compared to S+SE (7±1 inflammatory cells and 21±3 apoptotic cells) early post-operatively. In conclusion, each SMILE retreatment method resulted in unique tissue responses. S+SE offers advantages, such as minimal inflammation and cell death, as well as maintaining a ‘flap-less’ surgery, over other procedures. However, depending on the degree of enhancement, the lenticule may become too thin to be extracted and the procedure becomes more difficult to perform than S+C and S+P. S+P can maintain corneal integrity by avoiding flap creation and is technically more simple to perform than the others, but the surgery needs to be supplemented with mitomycin-C in order to reduce inflammation and modulate better wound healing.

Intraoperative centration during small incision lenticule extraction (SMILE)

To evaluate intraoperative decentration from pupil center and kappa intercept during small incision lenticule extraction (SMILE) and its impact on visual outcomes.This was a retrospective noncomparative case series. A total of 164 eyes that underwent SMILE at the Singapore National Eye Center were included. Screen captures of intraoperative videos were analyzed. Preoperative and 3 month postoperative vision and refractive data were analyzed against decentration.The mean preoperative spherical equivalent (SE) was -5.84 ± 1.77. The mean decentration from the pupil center and from kappa intercept were 0.13 ± 0.06 mm and 0.47mm ± 0.25 mm, respectively. For efficacy and predictability, 69.6% and 95.0% of eyes achieved a visual acuity (VA) of 20/20 and 20/30, respectively, while 83.8% and 97.2% of eyes were within ±0.5D and ±1.0D of the targeted SE. When analyzed across 3 groups of decentration from the pupil center (<0.1 mm, 0.1-0.2 mm, and >0.2 mm), there was no statistically significant association between decentration, safety, efficacy, and predictability. When analyzed across 4 groups of decentration from kappa intercept (<0.2 mm, 0.2-<0.4 mm, 0.4-<0.6 mm, and ≥0.6 mm), there was a trend toward higher efficacy for eyes with decentration of kappa intercept between 0.4 and <0.6 mm (P = .097). A total of 85.4% of eyes in the 0.4 to <0.6 mm group had unaided distance VA of 20/20 or better, as compared to only 57.8% of eyes in ≥0.6 mm group.Decentration of 0.13 mm from the pupil center does not result in compromised visual outcomes. Decentration of greater than 0.6 mm from the kappa intercept may result in compromised visual outcomes. There was a trend toward better efficacy in eyes which had decentered treatment from 0.4 to <0.6 mm from the kappa intercept. Patients with a large kappa intercept (>0.6 mm) should have their lenticule created 0.4 to 0.6 mm from the kappa intercept and not close to the pupil.

[Results of residual ametropia correction using CIRCLE technology after femtosecond laser SMILE surgery]

AIM

to evaluate functional results of reoperation performed according to the CIRCLE technology and using the VisuMax femtosecond laser and MEL-80 excimer laser in cases of regression of the refractive effect after SMILE surgery.

MATERIAL AND METHODS

We studied a group of post-SMILE patients. In those, who showed regression of the refractive effect at 1 year, reoperation was performed according to the CIRCLE technology and using the VisuMax femtosecond laser. The corneal flap was separated from the stromal bed and turned aside. Excimer laser ablation of the stromal bed was performed with the MEL 80 machine. The corneal flap was then placed back and rinsed from both sides. Uncorrected (UCVA) and corrected (BCVA) visual acuity as well as spherical equivalent (SE) were estimated before reoperation, on day 1, and at 1 month.

RESULTS

After reoperation, BCVA and UCVA improved. Patient refraction became close to emmetropia. Specifically, UCVA was 0.23±0.18 at baseline (i.e. 1 year after SMILE) and 0.93±0.11 after the CIRCLE procedure (p<0.05). The absolute value of SE was 1.86±1.15 D and 0±0 D before and after CIRCLE, respectively (p<0.05). BCVA change was not statistically significant - from 0.95±0.1 to 0.93±0.11 (p>0.05).

CONCLUSION

Reoperation performed according to the CIRCLE technology and using the VisuMax femtosecond laser and MEL-80 excimer laser provides an increase in visual acuity in case of post-SMILE regression of the refractive effect.

Enhancement after Small-Incision Lenticule Extraction: Incidence, Risk Factors, and Outcomes

PURPOSE

To report the incidence, risk factors, and outcomes of enhancement after small-incision lenticule extraction (SMILE).

DESIGN

Retrospective cohort study.

PARTICIPANTS

Five hundred twenty-four eyes of 307 patients who underwent SMILE at Singapore National Eye Center between February 2012 and March 2016.

METHODS

The data collected included patient age at primary SMILE, gender, race, preoperative and postoperative manifest refraction spherical equivalent (MRSE), preoperative and postoperative uncorrected distance visual acuity and corrected distance visual acuity, the occurrence of suction loss during the procedure, and the need for enhancement. All enhancements were carried out by performing an alcohol-assisted photorefractive keratectomy (PRK) procedure with application of mitomycin C (MMC).

MAIN OUTCOME MEASURES

Incidence, prevalence, preoperative and intraoperative risk factors for enhancement, and outcomes after enhancement.

RESULTS

The prevalence of enhancement was 2.7%, and 71.4% eyes had enhancement within 1 year of primary SMILE. The incidence of enhancement was 2.1% and 2.9% at 1 and 2 years, respectively. Age older than 35 years, preoperative MRSE more than -6.00 diopters (D), preoperative myopia more than 6.00 D, preoperative astigmatism more than 3.00 D, and intraoperative suction loss were significant risk factors for enhancement after SMILE after adjusting for all other covariates (odds ratios, 5.58, 4.80, 1.41, 3.06, and 2.14, respectively; P = 0.004, 0.021, 0.022, 0.002, and 0.020, respectively). In the patients who underwent bilateral SMILE, the first-operated eye had a marginal trend toward significance for enhancement (P = 0.054). There was no gender or racial difference. In the 14 eyes requiring enhancement, the uncorrected distance visual acuity before enhancement ranged from 20/80 to 20/25, and the mean attempted enhancement spherical equivalent was -0.50±0.86 D. The uncorrected distance visual acuity improved in most patients (92.9%) after enhancement.

CONCLUSIONS

The 2-year incidence of enhancement after SMILE was 2.9%. Risk factors associated with enhancement included older age at SMILE procedure, greater preoperative MRSE, greater preoperative myopia, greater preoperative astigmatism, and the occurrence of intraoperative suction loss. Clinical outcomes of using PRK with application of MMC for enhancement were good.

Refractive lenticule extraction (ReLEx) through a small incision (SMILE) for correction of myopia and myopic astigmatism: current perspectives

Small-incision lenticule extraction (SMILE) is an alternative to laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for the correction of myopia and myopic astigmatism. SMILE can be performed for the treatment of myopia ≤−12 D and astigmatism ≤5 D. The technology is currently only available in the VisuMax femtosecond laser platform. It offers several advantages over LASIK and PRK; however, hyperopia treatment, topography-guided treatment, and cyclotorsion control are not available in the current platform. The working principles, potential advantages, and disadvantages are discussed in this review.

Wound healing profiles of hyperopic-small incision lenticule extraction (SMILE)

Refractive surgical treatment of hyperopia still remains a challenge for refractive surgeons. A new nomogram of small incision lenticule extraction (SMILE) procedure has recently been developed for the treatment of hyperopia. In the present study, we aimed to evaluate the wound healing and inflammatory responses of this new nomogram (hyperopic-SMILE), and compared them to those of hyperopic-laser-assisted in situ keratomileusis (LASIK), using a rabbit model. A total of 26 rabbits were used, and slit lamp biomicroscopy, autorefractor/keratometer, intraocular pressure measurement, anterior segment optical coherence tomography, corneal topography, and in vivo confocal microscopy examinations were performed during the study period of 4 weeks. The corneas were then harvested and subject to immunofluorescence of markers for inflammation (CD11b), wound healing (fibronectin) and keratocyte response (HSP47). The lenticule ultrastructual changes were also analyzed by transmission electron microscopy. Out results showed that hyperopic-SMILE effectively steepened the cornea. Compared to hyperopic-LASIK, hyperopic-SMILE had less postoperative wound healing response and stromal interface reaction, especially in higher refractive correction. However, compared to myopic-SMILE, hyperopic-SMILE resulted in more central deranged collagen fibrils. These results provide more perspective into this new treatment option for hyperopia, and evidence for future laser nomogram modification.

Intra-Operative Cap Repositioning in Small Incision Lenticule Extraction (SMILE) for Enhanced Visual Recovery

PURPOSE

To study the role of intra-operative cap repositioning in acute visual recovery after small incision lenticule extraction (SMILE).

MATERIALS AND METHODS

Ninety-four eyes of 47 patients underwent the SMILE procedure for correction of myopic refractive error. Manifest refraction and visual quality parameters (optical quality analysis system) were evaluated before surgery. The Bowman's membrane was imaged using a handheld spectral domain optical coherence tomography device. All patients underwent an uneventful SMILE surgery by a single experienced surgeon. Intra-operative cap repositioning was done in the "right" eye of all patients (repositioned group) and the "left" eye of each patient served as controls (non-repositioned group). Visual acuity and optical quality were assessed 1 day and 1 week after surgery.

RESULTS

Bowman's membrane microdistortions were found in 21.3% of eyes in the repositioned group and 59.57% of the eyes in the non-repositioned group (p = 0.003) on the first day after surgery. Comparison of optical quality parameters was carried out between eyes where repositioning was done and control eyes (with and without microdistortions). On the first day after surgery, the modulation transfer function (MTF) and Strehl's ratio (SR) were significantly better in the repositioned group when compared with the controls (p = 0.002 and p = 0.003, respectively). Refractive error and lenticule thickness in eyes with microdistortions were similar (p > 0.05) between the two groups indicating other contributors to acute optical quality postoperatively.

CONCLUSIONS

Although the refractive error before surgery determines the extent of microdistortions, intra-operative cap repositioning can reduce them, thereby expediting acute visual recovery after SMILE.

Safety and efficacy of VisuMax® circle patterns for flap creation and enhancement following small incision lenticule extraction

Background

The purpose of this case series is to evaluate the safety and efficacy of VisuMax® Circle patterns in eyes that have undergone small incision lenticule extraction, thus creating a flap to perform an enhancement procedure or residual lenticule extraction.

Methods

This prospective, single center, case study series evaluated the use of a VisuMax® Circle pattern to create a corneal flap following small incision lenticule extraction. Patients were treated and followed at TRSC International LASIK Center (Bangkok, Thailand) for 3 months to assess the efficacy and safety of the procedure. Efficacy was determined by the surgeon’s ability to lift the created corneal flap.

Results

The study enrolled 28 eyes. Twenty-seven underwent the VisuMax® Circle pattern procedure for refractive enhancement, and one for residual lenticule extraction. In 100 % of cases (28 eyes) the lifting of the flap was possible, as planned. In all cases of refractive enhancement (27 eyes) by laser in situ keratomileusis (LASIK), the exposure of the stromal bed was sufficient for the necessary excimer laser ablation. No eyes lost two or more Snellen lines of corrected distance visual acuity (CDVA) and no procedure or flap-related complications or serious adverse events occurred.

Conclusions

This initial case series demonstrates that VisuMax® Circle pattern is efficacious and a suitable method to create a corneal flap for enhancement, following small incision lenticule extraction.

Visual and refractive outcomes of small incision lenticule extraction for the correction of myopia: 1-year follow-up

OBJECTIVE

To assess the 1 year clinical outcomes of small incision lenticule extraction (SMILE) for the correction of myopia and myopic astigmatism using a 500 kHz femtosecond laser system.

METHODS

This prospective study evaluated 52 eyes of 39 consecutive patients (31.8±6.9 years, mean age±SD) with spherical equivalents of -4.11±1.73 D (range, -1.25 to -8.25 D) who underwent SMILE for myopia and myopic astigmatism. Preoperatively, 1 week, and 1, 3, 6 and 12 months postoperatively, we assessed the safety, efficacy, predictability, stability, corneal endothelial cell loss and the adverse events of the surgery.

RESULTS

The logarithm of the minimal angle of resolution (logMAR) uncorrected distance visual acuity and LogMAR corrected distance visual acuity were -0.16±0.11 and -0.22±0.07, respectively, 1 year postoperatively. At 1 year, all eyes were within±0.5 D of the targeted correction. Manifest refraction changes of -0.05±0.32 D occurred from 1 week to 1 year postoperatively (p=0.20, Wilcoxon signed-rank test). The endothelial cell density was not significantly changed from 2804±267 cells/mm(2) preoperatively to 2743±308 cells/mm(2) 1 year postoperatively (p=0.12). No vision-threatening complications occurred during the observation period.

CONCLUSIONS

SMILE performed well in the correction of myopia and myopic astigmatism, and no significant change in endothelial cell density or any other serious complications occurred throughout the 1-year follow-up period, suggesting its viability as a surgical option for the treatment of such eyes.

Effect of Intraoperative Corneal Stromal Pocket Irrigation in Small Incision Lenticule Extraction

This study aimed at evaluating the effect of intraoperative corneal pocket irrigation in small incision lenticule extraction (SMILE) and compares it to that in femtosecond laser-assisted in situ keratomileusis (FS-LASIK). Sixteen rabbit eyes underwent a SMILE procedure, with 8 eyes having corneal pocket irrigation, while the other 8 eyes were without irrigation. Another 16 eyes underwent a FS-LASIK procedure for comparison, with 8 eyes having flap irrigation, while the other 8 eyes were without irrigation. The results showed that the changes in the total corneal thickness, anterior and posterior lamellar thickness, measured by the anterior segment optical coherence tomography, were comparable between the SMILE with and without irrigation groups, suggesting that the irrigation did not lead to significant changes in the corneal thickness. However, at postoperative 8 hours, in vivo confocal microscopy showed that the interface reflectivity in the SMILE with irrigation group was significantly higher than that in other three groups. The presence of interface fluid was further confirmed by the identification of fluid pockets with undulated collagen shown on histological section in the post-SMILE with irrigation eyes. Our findings might contribute to the occurrence of post-SMILE delayed immediate visual quality recovery and further clinical study is required.

Anterior and Posterior Corneal Astigmatism after Refractive Lenticule Extraction for Myopic Astigmatism

Purpose. To assess the amount and the axis orientation of anterior and posterior corneal astigmatism after refractive lenticule extraction (ReLEx) for myopic astigmatism. Methods. We retrospectively examined 53 eyes of 53 consecutive patients (mean age ± standard deviation, 33.2 ± 6.5 years) undergoing ReLEx to correct myopic astigmatism (manifest cylinder = 0.5 diopters (D)). Power vector analysis was performed with anterior and posterior corneal astigmatism measured with a rotating Scheimpflug system (Pentacam HR, Oculus) and refractive astigmatism preoperatively and 3 months postoperatively. Results. Anterior corneal astigmatism was significantly decreased, measuring 1.42 ± 0.73 diopters (D) preoperatively and 1.11 ± 0.53 D postoperatively (p < 0.001, Wilcoxon signed-rank test). Posterior corneal astigmatism showed no significant change, falling from 0.44 ± 0.12 D preoperatively to 0.42 ± 0.13 D postoperatively (p = 0.18). Refractive astigmatism decreased significantly, from 0.92 ± 0.51 D preoperatively to 0.27 ± 0.44 D postoperatively (p < 0.001). The anterior surface showed with-the-rule astigmatism in 51 eyes (96%) preoperatively and 48 eyes (91%) postoperatively. By contrast, the posterior surface showed against-the-rule astigmatism in all eyes preoperatively and postoperatively. Conclusions. The surgical effects were largely attributed to the astigmatic correction of the anterior corneal surface. Posterior corneal astigmatism remained unchanged even after ReLEx for myopic astigmatism.

Effect of femtosecond laser setting on visual performance after small-incision lenticule extraction for myopia

AIM

To compare the effect of the two femtosecond laser settings on visual performance after small-incision lenticule extraction (SMILE) for myopia and myopic astigmatism.

METHODS

Forty-four eyes of 22 consecutive patients who underwent SMILE with an energy level of 140 nJ (spot distance 3.0 µm) in one eye, and with an energy level of 170 nJ (spot distance 4.5 µm) in the other eye, the eyes being randomly assigned. Preoperatively, 1 week, and 1 and 3 months postoperatively, the values of the modulation transfer function (MTF) cutoff frequency, Strehl ratio, objective scattering index (OSI) and Optical Quality Analysis System (OQAS) values (OVs) for these eyes were quantitatively assessed using an Optical Quality Analysis System (Visiometrics).

RESULTS

No significant differences were detected between the two groups in the visual and refractive outcomes, or in the MTF cutoff frequency, the Strehl ratio, the OSI, the OV 100%, the OV 20% or the OV 9% at any time point before or after surgery.

CONCLUSIONS

SMILE with energy settings of 140 and 170 nJ was effective for the correction of myopia and myopic astigmatism. It is indicated that the differences in laser setting (140 nJ, spot distance 3.0 µm vs 170 nJ, spot distance 4.5 µm) did not significantly affect the optical quality including the intraocular scattering of eyes undergoing SMILE.

CLINICAL TRIAL NUMBER

The protocol was registered with University Hospital Medical Information Network Clinical Trial Registry (UMIN000016241).

New instruments for lenticule extraction in small incision lenticule extraction (SMILE)

Small incision lenticule extraction (SMILE) is an alternative to Laser-Assisted in situ Keratomileusis (LASIK) for correction of myopia. In cases where surgeons inadvertently dissect the posterior surface first, identification of the anterior surface and subsequent removal become difficult since the anterior surface of the lenticule is compacted against the anterior stromal surface. This may result in incomplete lenticule removal, and a remnant of intrastromal lenticule in SMILE may lead to visual sequelae. In order to aid surgeons in lenticule removal, we have designed and developed 5 novel SMILE lenticule strippers to locate and extract the lenticules more easily. The aim of this study was to investigate and compare the efficacy and quality of these lenticule strippers in assisting SMILE. Thirty porcine eyes were used. The ease of extraction and removal of the lenticule with different strippers was graded by an experienced SMILE surgeon, the extracted lenticule circularity was evaluated by calculating the lenticule circularity, and the intactness of the extracted lenticule edge was assessed using scanning electron microscopy. We found these novel strippers can be of great help to improve the safety and quality of SMILE surgery, particularly in those cases of difficult lenticule extraction.

Small incision lenticule extraction (SMILE) history, fundamentals of a new refractive surgery technique and clinical outcomes

This review summarizes the current status of the small incision lenticule extraction (SMILE) procedure. Following the early work by Sekundo et al. and Shah et al., SMILE has become increasingly popular. The accuracy of the creation of the lenticule with the VisuMax femtosecond laser (Carl Zeiss Meditec) has been verified using very high-frequency (VHF) digital ultrasound and optical coherence tomography (OCT). Visual and refractive outcomes have been shown to be similar to those achieved with laser in situ keratomileusis (LASIK), notably in a large population reported by Hjortdal, Vestergaard et al. Safety in terms of the change in corrected distance visual acuity (CDVA) has also been shown to be similar to LASIK. It was expected that there would be less postoperative dry eye after SMILE compared to LASIK because the anterior stroma is disturbed only by the small incision, meaning that the anterior corneal nerves should be less affected. A number of studies have demonstrated a lower reduction and faster recovery of corneal sensation after SMILE than LASIK. Some studies have also used confocal microscopy to demonstrate a lower decrease in subbasal nerve fiber density after SMILE than LASIK. The potential biomechanical advantages of SMILE have been modeled by Reinstein et al. based on the non-linearity of tensile strength through the stroma. Studies have reported a similar change in Ocular Response Analyzer (Reichert) parameters after SMILE and LASIK, however, these have previously been shown to be unreliable as a representation of corneal biomechanics. Retreatment options after SMILE are discussed. Tissue addition applications of the SMILE procedure are also discussed including the potential for cryo-preservation of the lenticule for later reimplantation (Mohamed-Noriega, Angunawela, Lim et al.), and a new procedure referred to as endokeratophakia in which a myopic SMILE lenticule is implanted into a hyperopic patient (Pradhan et al.). Finally, studies reporting microdistortions in Bowman's layer and corneal wound healing responses are also described.

Correction of myopic astigmatism with small incision lenticule extraction

PURPOSE

To evaluate the outcome after small incision refractive lenticule extraction (SMILE) in patients with myopic astigmatism.

METHODS

Seven hundred seventy-five eyes from 403 patients with myopia treated with SMILE for a cylinder of 0.75 diopters (D) or more were identified from patient records. Six hundred sixty-nine eyes were defined as receiving low (< 2.5 D) and 106 eyes as receiving high (⩾ 2.5 D) astigmatic correction. Patients were examined before and 3 months after surgery. SMILE was performed with a Visumax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). Preoperative and postoperative refractions were converted to polar values. Induced torsion and achieved corrections of sphere and cylinder were determined.

RESULTS

In low astigmatism, the mean preoperative spherical equivalent (SE) was -7.57 ±1.67 D and the cylinder was -1.22 ± 0.49 D. Three months after surgery, SE was -0.19 ± 0.48 D from target, astigmatism was 0.17 ± 0.42 D undercorrected, and a small but significant torsion of the cylinder axis corresponding to 0.05 ± 0.37 D was found. The astigmatic undercorrection measured 13% per diopter of attempted correction. In high astigmatism, preoperative SE was -5.91 ± 2.56 D and cylinder was -3.22 ± 0.67 D. After surgery, the average astigmatic undercorrection was 0.59 ± 0.65 D, equivalent to 16% per diopter of attempted correction. No undercorrection in SE occurred and no torsion was found.

CONCLUSIONS

SMILE in myopic astigmatism offers predictable correction of SE, but a small, significant undercorrection of the astigmatic error. The undercorrection increases with the attempted treatment. Only very little rotation of the cylinder axis was found.

Past and present of corneal refractive surgery: a retrospective study of long-term results after photorefractive keratectomy and a prospective study of refractive lenticule extraction

Surgical correction of refractive errors is becoming increasingly popular. In the 1990s, the excimer laser revolutionized the field of corneal refractive surgery with PRK and LASIK, and lately refractive lenticule extraction (ReLEx) of intracorneal tissue, using only a femtosecond laser, has become possible. Two new procedures were developed, ReLEx flex (FLEX) and ReLEx smile (SMILE). Until this thesis, only a few long-term studies of PRK with a relatively limited number of patients had been published; therefore, this thesis intended to retrospectively evaluate long-term outcomes after PRK for all degrees of myopia for a large number of patients. Furthermore, a prospective contralateral eye study comparing FLEX and SMILE, when treating high to moderate degrees of myopia, had not been performed prior to this study. This was the second aim of this thesis. In the first study, results from 160 PRK patients (289 eyes) were presented. Preoperative spherical equivalent ranged from -1.25 to -20.25 D, with 78% having low myopia (<-6 D). Average follow-up time was 16 years (range 13-19 years), making this the longest published follow-up study on PRK patients. Outcomes from eyes with low myopia were generally superior to outcomes from eyes with high myopia, at final follow-up. Seventy-two percent were within ± 1.00 D of target refraction, as compared to 47% of eyes with high myopia. However, results from a subgroup of unilateral treated PRK patients indicated that refraction at final follow-up was affected by myopic progression. Fifty percent of eyes with low myopia had uncorrected 20/20 distance visual acuity or better, as compared to 22% of eyes with high myopia. Haze did not occur if attempted corrections were <-4 D, and only eyes with high myopia lost two lines or more of CDVA (corrected distance visual acuity). Eighty-one per cent were satisfied or very satisfied with their surgery.

CONCLUSION

The results support the continued use of the excimer laser for corneal surface ablation as a treatment option for correction of low degrees of myopia, and as the treatment of choice for subgroups of refractive patients (thin corneas, etc.). The results also highlight that treatment of higher degrees of myopia with standard PRK should only be done today under special circumstances, due to low refractive predictability, and high risk of corneal haze. Technological advances since then should be taken into account when comparing these results with contemporary techniques. In the second study, 35 patients were randomized to receive FLEX in one eye and SMILE in the other. Preoperative spherical equivalent refraction ranged from -6 to -10 D with low degrees of astigmatism. A total of 34 patients completed the 6 month follow-up period. Refractive and visual outcomes were very similar for the two methods, as well as tear film measurements and changes in corneal biomechanics. Ninety-seven percent were within ± 1.00 D of target refraction, no eyes lost two lines or more of CDVA, and contrast sensitivity was unaffected after both procedures. The changes in higher-order aberrations were also very similar. There were also no differences in tear film parameters 6 months after surgery, although less postoperative foreign body sensation was reported within the first week after surgery in SMILE eyes. Corneal sublayer pachymetry measurements demonstrated equally increased epithelial thickness 6 months after surgery. Contrary to expectations, it was not possible to measure the theoretical biomechanical advantages of a small corneal incision in SMILE as compared to a corneal flap in FLEX. The main differences between FLEX and SMILE were found when the corneal nerves and intraoperative complications were evaluated. Thus, corneal sensitivity was better preserved and corneal nerve morphology was less affected after SMILE, but intraoperative complications occurred more frequently, although without visual sequela. Finally, 97% were satisfied or very satisfied with both their surgeries.

CONCLUSION

The results support the continued use of both FLEX and SMILE for treatment of up to high degrees of myopia. Overall, refractive and visual results for both procedures were good and similar, but from a biological point of view, the less invasive SMILE technique is more attractive, as demonstrated in this study, despite being slightly more surgically demanding than FLEX.

Advances in Refractive Surgery

PURPOSE

The objective of this study was to review advances in the field of refractive surgery as reported in the peer-reviewed literature over the previous year.

DESIGN

This was a literature review.

METHODS

We conducted a PubMed search for terms related to refractive surgery and reviewed prominent international ophthalmic journals published from May 2012 through April 2013. All pertinent articles were reviewed, and selected articles with the greatest relevance were included.

RESULTS

Many studies over the previous year have highlighted progress in the field of refractive surgery; topics included keratoconus screening, photorefractive keratectomy and laser in situ keratomileusis, corneal cross-linking, small-incision lenticule extraction, phakic intraocular lenses, corneal inlays, presbyopic corneal treatments, and femtosecond laser-assisted astigmatic keratotomy.

CONCLUSIONS

The field of refractive surgery continues to provide exciting developments. Improvements in established procedures and promising new surgical options make the current climate an appealing one for refractive surgeons and patients.