Comparing a new hydroexpression technique with conventional forceps method for SMILE lenticule removal

Modified Technique for Small-Incision Lenticule Extraction: Ye's Swing Technique

INTRODUCTION

This study aimed to evaluate the lenticule integrity and refractive outcomes of a new technique, Ye's swing technique, during small-incision lenticule extraction (SMILE).

METHODS

This prospective study enrolled patients who underwent the SMILE procedure using a modified technique for lenticule dissection. Per the standard SMILE procedure, the cap cut was opened using a hook, and an anterior dissection was performed with a counterclockwise swing, from 8 to 12 o'clock. A posterior dissection was then performed by swinging counterclockwise, leaving a thin band of the peripheral rim undissected, from 8 to 4 o'clock. The counterclockwise swing was continued to separate the edges of the rim from 4 to 12 o'clock, after which microforceps were used to extract the lenticules. The primary outcome measures were safety and lenticule integrity at the end of the surgery, and the secondary outcome measure was efficacy. Changes in the ocular parameters from the preoperative visit to 1 month postoperative, including uncorrected and corrected distance visual acuity, manifest refraction, lenticule quality, and lenticule residual, were assessed using optical coherence tomography.

RESULTS

A total of 246 patients (490 eyes) with myopia and myopic astigmatism were included in the present study. The dissected lenticules ranged in size from 52 to 148 µm. Postoperatively, the lenticule was completely and successfully extracted in all cases. There was no incisional edge tearing during lenticule separation.

CONCLUSIONS

Ye's swing technique is a safe and effective procedure for lenticule dissection and refractive outcomes. We have now adopted this technique as our routine method for performing the SMILE procedure.

Research Progress on Morphological Changes and Surgery-related Parameters of Corneal Cap in Small Incision Lenticule Extraction

Small incision lenticule extraction (SMILE) is an "all-in-one" surgical method for refractive correction. An advantage of the SMILE over traditional surgery is that it depends on the corneal cap's design. This review discusses the morphological evaluation of the corneal cap, selection of the corneal cap with different thickness and diameters, influence of the corneal cap design on retreatment, and management of corneal cap-related complications. The following points should be recognized to define the correct morphology and design of the operation-related parameters of the corneal cap during SMILE: (1) the thickness and diameter of the corneal cap are predictable and influence postoperative visual quality, (2) the change in anterior surface curvature of the corneal cap should be considered in the design of nomogram value, (3) for patients with moderate myopic correction, early visual quality is better with a 6.9-mm than with a 7.5-mm diameter corneal cap, (4) there is no significant difference in visual quality or biomechanics among corneal caps with different thickness; (5) primary corneal cap thickness plays an important role in the SMILE retreatment, (6) a 7.78-mm diameter corneal cap has a greater risk of suction loss than a 7.60-mm diameter corneal cap, (6) if suction loss occurs when lenticular scanning exceeds 10%, then SMILE can be continued by changing corneal cap thickness, (7) preventive collagen cross-linking with SMILE caps are 90-120 μm thick and 7-7.8 mm in diameter, and (8) properly treating SMILE-related complications ensures better postoperative results. The data presented herein shall deepen the understanding of the importance of the corneal cap during SMILE and provide diversified analysis for personalized operational design of corneal cap parameters.

Corneal lenticule extraction assisted by a low-energy femtosecond laser

A lenticule of intrastromal corneal tissue was cut together with 2 small incisions of 3.0 mm using a low-energy femtosecond laser system, FEMTO LDV Z8; 1 incision led to the posterior plane and 1 to the anterior, allowing dissection of the lenticule. When needed, recentering of the treatment area was possible without repeating the docking stage. Five eyes were operated, and a complete dissection and removal of the lenticule was achieved in all cases without any intraoperative complications. In addition, at postoperative day 1, all patients had a clear cornea. In conclusion, guided lenticule extraction using a low-energy femtosecond laser was a promising and easy procedure.

Inverse centripetal dissection: A rescue technique for mis-dissected lenticule during SMILE

Management of mis-dissected lenticule during Small-incision lenticule extraction (SMILE) is technically challenging and might be experienced more by novice surgeons especially in eyes with low refractive errors and thin lenticules. Presently, we describe a rescue method of inverse centripetal dissection (ICD) to manage mis-dissected lenticules. In this technique, after inadvertent dissection of posterior plane prior to anterior plane, the double-ended SMILE dissector is rotated along its shaft axis clockwise from the left upper margin of the mis-dissected lenticule to form an inversely folded lenticule which is then subsequently dissected centripetally till midline. This is then extracted by performing lenticulorrhexis with a pair of microforceps. We performed this technique in 10 eyes of 10 patients and the lenticule extraction was accomplished successfully in all eyes. At six months follow-up, the uncorrected visual acuity was 20/20 with a clear interface in all eyes. The ICD approach might serve as a useful rescue technique for managing mis-dissected lenticules.

Advances in refractive corneal lenticule extraction

Refractive errors are the leading cause of reversible visual impairment worldwide. In addition to the desired spectacle independence, refractive procedures can improve quality of life, working ability, and daily working performance. Refractive corneal lenticule extraction (RCLE) is a relatively new technique, dependent only on a femtosecond laser (FS). This leads to potential benefits over laser-assisted in situ keratomileusis (LASIK) including a quicker recovery of dry eye disease, a larger functional optical zone, and no flap-related complications. SMILE, available with the VisuMax FS (Carl Zeiss Meditec AG, Jena, Germany), is the most established RCLE application, offering visual and refractive outcomes comparable to LASIK. SmartSight (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany) and CLEAR (Ziemer Ophthalmic Systems AG, Port, Switzerland) are two new RCLE applications that received Conformité Européenne (CE) approval in 2020. In this article, we review refractive and visual outcomes, advantages, and disadvantages of RCLE and also report on the latest advances in RCLE systems.

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.

Effect of corneal stromal pocket irrigation in small-incision lenticule extraction

Objectives

To investigate the effect of corneal stromal pocket irrigation after small-incision lenticule extraction (SMILE) on visual acuity, intraocular pressure (IOP), corneal parameters and complications after surgery.

Methods

A total of 242 eyes of 121 patients undergoing SMILE were enrolled in this prospective controlled study, and it was designed for one eye to randomly undergo SMILE with balanced salt solution irrigation of the corneal stromal pocket, while the other eye was not. The uncorrected distance visual acuity (UDVA) and slit lamp examination were recorded at 1 hour, 1 day, 1 week, and 1 month. Postoperative corneal density, corneal biomechanical, corneal endothelial cell number, and anterior OCT images were compared at 1 day, 1 week, and 1 month.

Results

Compared with the nonirrigation group, the irrigation group showed significantly higher UDVA at 1 day postoperatively (P < 0.05), but there was no significant difference during the rest of the postoperative period (1 hour, 1 week, and 1 month). In addition, no significant differences were found in IOP, corneal density, corneal biomechanics, corneal endothelial cells, and corneal morphology. No visual decline or severe postoperative complications were found in the patients in this study.

Conclusions

Interlamellar irrigation did not affect IOP, corneal parameters, morphology, complications, or UDVA at 1 hour, 1 week, and 1 month after the operation, but it may promote UDVA 1 day after the operation.

Astigmatism Correction Using SMILE

Small incision lenticule extraction (SMILE) was introduced in the recent decade for the treatment of myopia and myopic astigmatism. This flap-free technique has a high efficacy and safety profile and also carries potential advantages over laser in situ keratomileusis such as a better corneal biomechanical stability, reduction in dry eyes rate, and the avoidance of flap complications. However, there have been concerns regarding the precision of astigmatism correction that undercorrection has been reported to be apparent. Various factors that affect astigmatism correction have been identified in the literature. The purpose of this review is to discuss the factors that affect astigmatism correction in SMILE and several techniques to improve the refractive outcomes.

Flushing versus not flushing the interface during small-incision lenticule extraction

PURPOSE

To assess the differences in outcomes between interface flushing with a balanced salt solution after refractive lenticule removal in simultaneous uneventful bilateral small-incision lenticule extraction (SMILE).

SETTING

Six study centers in Germany.

DESIGN

Prospective case series.

METHODS

Patients with myopia or myopic astigmatism of similar magnitude in both eyes with a spherical equivalent less than or equal to 10.0 diopters (D), preoperative corrected distance visual acuity (CDVA) of 0.80 decimal or better, and anisometropia less than or equal to 2.0 D were enrolled and followed for 3 months. One eye of each patient was treated with interface flushing after dry extraction of the lenticule. Flushing was performed with 1.0 cc balanced salt solution using a single-use 27-gauge cannula. The uncorrected distance visual acuity (UDVA) at 1 day, 1 week, and 3 months; the CDVA at 3 months; and postoperative differences at the slitlamp examination were recorded. Statistical analyses were performed with logarithm of the minimum angle of resolution values using paired t tests. The P value for significance was less than 0.05.

RESULTS

The study analyzed 470 eyes. One day postoperatively, the mean UDVA was 0.81 in the non-flush group and 0.83 in the flush group (P = .110). At the last visit 3 months postoperatively, the mean UDVA was 1.04 and 1.05, respectively (P = .172). No significant differences in the rate of postoperative complications were found.

CONCLUSION

Interface irrigation with 1.0 cc of balanced salt solution after the removal of the refractive lenticule has neither advantages nor disadvantages in terms of visual recovery, postoperative complications, or final visual acuity.

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.