Femtosecond lenticule extraction for the correction of myopia: preliminary 6-month results

Twelve-year global publications on small incision lenticule extraction: A bibliometric analysis

Purpose

To analyze the development process of small incision lenticule extraction (SMILE) surgery in a 12-year period.

Methods

We conducted a literature search for SMILE research from 2011 to 2022 using the Science Citation Index Expanded (SCIE) of the Web of Science Core Collection (WoSCC). The VOS viewer, and CiteSpace software were used to perform the bibliometric analysis. Publication language, annual growth trend, countries/regions and institutions, journals, keywords, references, and citation bursts were analyzed.

Results

A total of 731 publications from 2011 to 2022 were retrieved. Annual publication records grew from two to more than 100 during this period. China had the highest number of publications (n = 326). Sixty-five keywords that appeared more than four times were classified into six clusters: femtosecond laser technology, dry eye, biomechanics, visual quality, complications, and hyperopia.

Conclusion

The number of literatures has been growing rapidly in the past 12 years. Our study provides a deep insight into publications on SMILE for researchers and clinicians with bibliometric analysis for the first time.

Effect of preoperative keratometry on visual outcomes after small-incision lenticule extraction for myopia

PURPOSE

To investigate the relationship between preoperative keratometry (K) and postoperative refraction and compare the visual outcomes after small-incision lenticule extraction (SMILE) between preoperative flat and steep corneas.

METHODS

This study involved 814 consecutive eyes of 409 patients who underwent SMILE. A month later, a linear regression analysis of the relationship between preoperative K and the residual spherical equivalent (SE) along with eyes divided by a single standard deviation between flat and steep corneas (< 41.85 D, > 44.57 D, respectively) was conducted. Eyes were distinguished based on the degree of myopia.

RESULTS

One month after surgery, no significant correlation existed between mean preoperative K and residual SE (P = 0.459). Linear regression analysis showed a weak negative correlation between flat corneas (r2 = 0.042, P = 0.025) rather than steep corneas (P = 0.908). Eyes with preoperative low myopia (< 3.00 D) (r2 = 0.233, P = 0.001) had a weak correlation compared with moderate and high myopia (P = 0.272, P = 0.257, respectively). Twelve months later, the predictability, safety, and efficacy did not vary between preoperative flat and steep corneas (P > 0.05).

CONCLUSIONS

One month after SMILE for myopia, the corneas were flatter in the preoperative flat corneas or all the low myopic corneas, and they were more overcorrected. However, preoperative corneal curvature does not influence visual outcomes at 1 year after SMILE.

Bilateral Lenticule Creation Followed by Bilateral Lenticule Separation Improves Visual Outcomes After SMILE

PURPOSE

To explore the impact of different surgical sequences on the visual and refractive outcomes of bilateral small incision lenticule extraction (SMILE) surgery using propensity score matching (PSM) analysis.

METHODS

Participants who underwent uneventful SMILE between March 2018 and September 2019 were retrospectively analyzed and were divided into two groups: Sequence A (laser scanning [LS] of the right eye, manual separation lenticule [MSL] of the right eye, and LS and MSL of the left eye) and Sequence B (LS of the right eye, LS of the left eye, MSL of the left eye, and MSL of the right eye). PSM was conducted to minimize the effect of confounding factors on postoperative visual outcomes at days 1 and 7 and months 1, 3, and 6. Safety, efficacy, predictability, and stability were compared between groups.

RESULTS

Overall, 1,854 eyes of 927 participants were included (Sequence A, n = 280; Sequence B, n = 647). After PSM, there were no significant differences in baseline characteristics, and 534 eyes (267 patients) in the Sequence A group were matched (1:1) to the Sequence B group. The postoperative corrected distance visual acuity significantly differed between groups at 3 months (adjusted P = .007). The uncorrected distance visual acuity significantly differed between groups at all follow-up visits (adjusted P < .01). The safety index (1.341 ± 0.265 and 1.413 ± 0.294) and efficacy index (1.173 ± 0.191 and 1.251 ± 0.269) were different in the Sequence A and Sequence B groups, respectively, at 3 months (adjusted P < .01). No difference in visual outcomes was found between right and left eyes.

CONCLUSIONS

Patients who had bilateral lenticule creation followed by bilateral lenticule separation had better postoperative visual outcomes than those who underwent complete SMILE surgery in each eye separately. Regardless of the surgical sequence chosen for the SMILE procedure, there was no impact on outcomes between the right and left eyes. Adjusting the sequence of the surgical procedure may be a way to improve the visual results. [J Refract Surg. 2021;37(11):726-733.].

Mid-Infrared Few-Cycle Pulse Generation and Amplification

In the past decade, mid-infrared (MIR) few-cycle lasers have attracted remarkable research efforts for their applications in strong-field physics, MIR spectroscopy, and bio-medical research. Here we present a review of MIR few-cycle pulse generation and amplification in the wavelength range spanning from 2 to ~20 μm. In the first section, a brief introduction on the importance of MIR ultrafast lasers and the corresponding methods of MIR few-cycle pulse generation is provided. In the second section, different nonlinear crystals including emerging non-oxide crystals, such as CdSiP2, ZnGeP2, GaSe, LiGaS2, and BaGa4Se7, as well as new periodically poled crystals such as OP-GaAs and OP-GaP are reviewed. Subsequently, in the third section, the various techniques for MIR few-cycle pulse generation and amplification including optical parametric amplification, optical parametric chirped-pulse amplification, and intra-pulse difference-frequency generation with all sorts of designs, pumped by miscellaneous lasers, and with various MIR output specifications in terms of pulse energy, average power, and pulse width are reviewed. In addition, high-energy MIR single-cycle pulses are ideal tools for isolated attosecond pulse generation, electron dynamic investigation, and tunneling ionization harness. Thus, in the fourth section, examples of state-of-the-art work in the field of MIR single-cycle pulse generation are reviewed and discussed. In the last section, prospects for MIR few-cycle lasers in strong-field physics, high-fidelity molecule detection, and cold tissue ablation applications are provided.

Early Corneal Wound Healing Response After Small Incision Lenticule Extraction

PURPOSE

To evaluate the corneal wound healing response after small incision lenticule extraction surgery.

METHODS

Small incision lenticule extraction was performed in both eyes of 12 New Zealand White rabbits. The refractive spherical correction was set at -6.00 D. Two animals were analyzed at each time point (1 hour, 4 hours, 1 day, 3 days, 7 days, and 28 days). The corneas were evaluated using slit-lamp and in vivo confocal microscopy. After euthanatization, the corneal tissues were subjected to light microscopy, transferase 2'-Deoxyuridine 5'-Triphosphate (dUTP) nick end labeling assay, and immunofluorescence microscopy (CD11b, fibronectin, tenascin, alpha-smooth muscle actin [α-SMA]).

RESULTS

The corneas did not show any opacity at any time point except at the side-cut incision. By contrast, there was obvious scar tissue at the side-cut incision. Scattered, hyperreflective spots were seen by confocal microscopy from 1 hour postoperatively. Transferase dUTP nick end labeling-positive keratocytes were abundant near the femtosecond laser incision area at 1 hour and reached a peak at 4 hours postoperatively and then decreased. Inflammatory cells migrated from the incision into the central cornea, and this process began 1 hour after surgery and peaked at 7 days. Extracellular matrix components were deposited at the beginning of day 1 postoperatively, and the distribution pattern differed between the central cornea and the incision site. α-SMA-positive myofibroblasts were only detected at the side-cut incision.

CONCLUSIONS

The scar tissue response in the peripheral cornea is related to the epithelium debridement. Inflammatory cells begin to be recruited by 1 hour after surgery. Therefore, it is necessary to implement antiinflammation interventions at a very early stage.

Application of the SMILE-derived lenticule in therapeutic keratoplasty

PURPOSE

To observe the clinical efficacy of the small incision lenticule extraction (SMILE)-derived lenticule patch graft in therapeutic keratoplasty, especially for the treatment of corneal microperforation or partial-thickness corneal defects.

METHODS

Corneal lenticule obtained from SMILE surgery with diameter greater than 6.5 mm and thickness greater than 100 μm was preserved in a balanced salt solution (Alcon Laboratories, Fort Worth, TX) containing 50 mg/mL penicillin, 50 mg/mL streptomycin, 100 mg/mL neomycin, and 2.5 mg/mL amphotericin for at least 3 months. Preoperatively, anterior segment optical coherence tomography was used to assess the depth of the ulcer and to decide the thickness of the lenticule. Patients were followed up on day 1 and then at 1, 3, and 6 months postoperatively.

RESULTS

Corneal perforation or defects were successfully patched in all 17 eyes; 8 eyes (47%) exhibited improvement postoperative corrected distance visual acuity. During the follow-up period of 6 months, there was no evidence of infection, relapse, or perforation detected in all eyes. Lenticule grafts were attached by graft beds very well and remain clear through to the last follow-up checkup in all eyes treated.

CONCLUSIONS

The lenticule patch graft seems to serve as a safe, feasible, and inexpensive surgical option for the treatment of keratohelcosis or partial-thickness corneal defects, especially in small perforation and defects. There are hopeful signs that SMILE-derived lenticule becomes a potential graft for therapeutic keratoplasty.

10-Year Results of FLEx Refractive Surgery

PURPOSE

To evaluate the 10-year results of femtosecond lenticule extraction (FLEx) for treatment of myopia and myopic astigmatism.

METHODS

This long-term follow-up of a prospective clinical trial was conducted at HELIOS Klinikum Erfurt and Phillips University of Marburg, Germany. In 2006, 108 eyes underwent the FLEx procedure. All patients were invited for reexamination 10 years after FLEx treatment for myopia and astigmatism. Visual acuity, objective and manifest refraction, intraocular pressure, and slit-lamp examination and side effects were documented. Main outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuity, objective and manifest refraction, and slit-lamp examination and side effects.

RESULTS

A total of 77 eyes of 40 patients of the original treatment group volunteered for a reexamination 10 years after surgery. The mean age of the patients was 45.9 years; 26 were women and 14 were men. UDVA was 0.09 ± 0.19 logMAR and CDVA was stable at -0.1 ± 0.09 logMAR. More than half of the eyes gained one or two Snellen lines, and none of the eyes lost two or more lines. Over the 10-year period, regression was 0.18 D.

CONCLUSIONS

FLEx has stable results 10 years after treatment for myopia and astigmatism. [J Refract Surg. 2019;35(11):707-711.].

Comparing Patient-Reported Outcomes of Laser In Situ Keratomileusis and Small-Incision Lenticule Extraction: A Review

PURPOSE

Laser in situ keratomileusis (LASIK) and small-incision lenticule extraction (SMILE) are popular refractive surgeries. The objective refractive outcomes of LASIK and SMILE have been studied extensively; both procedures have comparable safety, efficacy, and predictability. However, owing to various psychosocial factors, refractive patients may report dissatisfaction despite good postoperative vision. Hence the importance of studies on subjective patient-reported outcomes. This review discusses the role of psychometric-technique-based validated questionnaires when evaluating subjective outcomes. It also summarizes the literature on patient-reported outcomes for LASIK and SMILE.

DESIGN

A literature search was performed on PubMed database to identify studies that have assessed patient-reported outcomes for LASIK and SMILE.

RESULTS

Several studies have looked into patient-reported outcome measures for LASIK, but the number of equivalent studies for SMILE is limited. Questionnaires (validated and non-validated) are used to evaluate patient-reported outcomes. Validated questionnaires are designed based on psychometric techniques, such as Classic Test Theory, Item Response Theory, and Rasch analysis. The Quality of Life Impact of Refractive Correction (QIRC) questionnaire, a validated questionnaire administered to both LASIK and SMILE patients, suggests that both groups have comparable vision-related quality of life in the first few months postoperatively; but SMILE might confer a slight advantage in the later postoperative period (postoperative month 6).

CONCLUSIONS

Future LASIK-SMILE comparative studies utilizing standardized validated questionnaires for patient-reported outcome measures with longer follow-up durations would be a welcome contribution to this important aspect of refractive surgery.

The comparison of visual outcomes, aberrations, and Bowman's layer micro-distortions after femtosecond laser small-incision lenticule extraction (SMILE) for the correction of high and moderate myopia and myopic astigmatism

Background

This study compares the clinical outcomes of femtosecond laser small-incision lenticule extraction (SMILE) for the correction of myopia and myopic astigmatism greater than − 10 D, and − 10 D or less respectively.

Methods

60 eyes/patients were equally selected into group 1 (myopia and myopic astigmatism of − 10 D or less) and group 2 (myopia and myopic astigmatism of over − 10 D), both of which were treated with SMILE. Visual and refractive outcomes, corneal higher-order aberrations, and Bowman’s layer micro-distortions were evaluated preoperatively, 3 months, and 6 months postoperatively.

Results

LogMAR corrected distance visual acuity (CDVA) of group 1 and group 2 was − 0.069 ± 0.047 and − 0.053 ± 0.073 6 months postoperatively (P = 0.48). 100% eyes in group 1 and 97% in group 2 were within 1 D of targeted correction (P = 0.45). Meanwhile, 100% eyes in group 1 and 97% in group 2 had an uncorrected distance visual acuity of 20/25 or better (P = 0.20). Changes in corneal higher-order aberrations root mean square, coma, and trefoil were similar between the two groups but spherical aberration was higher in group 2 (P < 0.01). Micro-distortions were observed in 53% in group 1 and 77% in group 2. More micro-distortions were observed in group 2 (3.40 ± 2.66) than in group 1 (2.07 ± 2.29) (P = 0.041). The total number of micro-distortions was not correlated with postoperative CDVA (P = 0.77).

Conclusions

Visual outcomes showed similar results of SMILE for myopic correction of > − 10 D and ≤ − 10 D. Refractive outcomes showed slightly under-correction in higher myopic eyes. Higher myopic treatment tends to induce more spherical aberrations. Micro-distortions had no impact in visual and refractive outcomes.

Visual and optical quality outcomes of SMILE and FS-LASIK for myopia in the very early phase after surgery

BACKGROUND

Small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) are frequently used to treat myopia. However, little is known about the impact on recovery of these approaches in the very early postsurgical phase (within 24 h).

METHODS

To compare the efficacy of these two procedures for the treatment of myopia in the early phase after surgery, differences in visual acuity, OSI (objective scattering index), cutoff for modulation transfer function (MTF), and SR (Strehl ratio) between SMILE and FS-LASIK were evaluated at 0, 2, 4 and 24 h postoperatively using two-way analysis of variance (ANOVA).

RESULTS

No significant differences between SMILE and FS-LASIK in the MTF cutoff and SR were found (p > 0.05). However, at 2 h and 4 h after surgery, OSI values in the SMILE group were significantly higher than those in the FS-LASIK group, and visual acuity scores in the SMILE group were significantly poorer than those in the FS-LASIK group (p < 0.05). Regarding subjective symptoms, the number of patients complaining of eye dryness, blurred vision, foreign body sensation and eye soreness in the SMILE group were lower than the number in the FS-LASIK group.

CONCLUSIONS

In conclusion, visual and optical quality outcomes of FS-LASIK for myopia were better than those of SMILE in the very early phase after surgery, a difference that is attributable to the formation of interface haze.

TRIAL REGISTRATION

ChiCTR1900021451 .

Quality of life after refractive surgery: ReLEx SMILE vs Femto-LASIK

Purpose

The safety and effectiveness of complex myopic astigmatism correction using ReLEx SMILE or Femto-LASIK techniques have been well established. The purpose of the current study is to compare quality of life (QoL) outcomes following ReLEx SMILE or Femto-LASIK procedures in parallel with functional vision and anatomic outcomes of treated eyes.

Patients and methods

This prospective, consecutive series included 118 patients, 18–43 years of age, out of which 56 underwent ReLEx SMILE and 62 underwent Femto-LASIK surgery for correction of myopic astigmatism. All patients underwent standard comprehensive ophthalmic examinations, and additionally, completed The Quality of Life Impact of Refractive Correction Questionnaire to determine the impact the vision-correction treatment had on their QoL.

Results

In both treatment groups, the postoperative refractive outcomes were comparable, with visual acuity improvements for both groups noted the day following surgery. After laser correction of complex myopic astigmatism using Femto-LASIK and ReLEx SMILE methods, the overall QoL indicators are statistically significant (P<0.01) exceeding preoperative values 1 month after the operation and reaching the maximum values by the end of the observation period (P<0.0001).

Conclusion

The results of the study suggest that patients require some time to adapt to their new visual function and its impact on their daily living, delaying detectable improvements in QoL. Moreover, these results may suggest a higher satisfaction trend and long-term QoL in patients undergoing ReLEx SMILE in comparison to Femto-LASIK. Long-term results from the study demonstrated high patient satisfaction with both methods.

[Condition of corneal nerve fibers after laser keratorefractive surgery]

The article reviews studies dedicated to evaluation of corneal nerve fibers (CNF) after various laser keratorefractive methods of correcting refractive error based on confocal microscopy. The matter of studying the dynamics of the condition of CNF after laser keratorefractive techniques continues to be relevant and requires further research with regard to the prevalence of refractive errors on the one hand, and the future life of patients who undergo these procedures, on the other. Certain heterogeneity of the research results presented in this review can be partially explained by the subjective nature of the study algorithm (in particular, the need for manual tracing of nerve fibers) and the lack of objective quantitative indicators of CNF condition suitable for statistical processing.

Simulated night vision after small-incision lenticule extraction

PURPOSE

To describe simulated night vision, night-vision symptoms, and refractive outcomes after small-incision lenticule extraction.

SETTING

Tertiary referral eye center, Singapore.

DESIGN

Prospective case series.

METHODS

All patients had small-incision lenticule extraction using the Visumax 500 kHz femtosecond laser system. The main outcome measure was simulated night vision logMAR corrected distance visual acuity (CDVA) using the super vision test-night vision goggle vision chart at 12 months. Secondary outcomes measures included refractive outcomes (ie, efficacy, predictability, and safety) up to 12 months and vision-related symptoms assessed using a validated questionnaire.

RESULTS

The study comprised 50 eyes. Overall simulated night vision was not affected (mean CDVA 0.08 logMAR ± 0.1 [SD], P = .67; mean mesopic CDVA -0.02 ± 0.1 logMAR, P = .58) after small-incision lenticule extraction at the 12-month follow-up. In low myopia, simulated night vision improved from preoperatively (mean 0.099 ± 0.07) to 12 months postoperatively (mean 0.006 ± 0.09) (P = .008). Most patients reported mild or no night-vision symptoms 3 months after surgery (score range 1.6 to 2.2). At 12 months, the overall efficacy index was 0.98 ± 0.20, with 100% of eyes attaining an uncorrected visual acuity of 20/40 or better and 86% attaining 20/20 or better. Ninety-four percent eyes were within ±1.0 diopter of the attempted correction, and the overall safety index was 1.17 ± 0.17.

CONCLUSION

Small-incision lenticule extraction did not affect simulated night vision or contrast sensitivity, with patients reporting no or mild night-vision symptoms.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Hyperopic refractive correction by LASIK, SMILE or lenticule reimplantation in a non-human primate model

Hyperopia is a common refractive error, apparent in 25% of Europeans. Treatments include spectacles, contact lenses, laser interventions and surgery including implantable contact lenses and lens extraction. Laser treatment offers an expedient and reliable means of correcting ametropia. LASIK is well-established however SMILE (small-incision lenticule extraction) or lenticule implantation (derived from myopic laser-correction) are newer options. In this study we compared the outcomes of hyperopic LASIK, SMILE and lenticule re-implantation in a primate model at +2D/+4D treatment. While re-implantation showed the greatest regression, broadly comparable refractive results were seen at 3-months with SMILE and LASIK (<1.4D of intended), but a greater tendency to regression in +2D lenticule reimplantation. Central corneal thickness showed greater variation at +2D treatment, but central thickening during lenticule reimplantation at +4D treatment was seen (-17± 27μm LASIK, -45 ± 18μm SMILE and 28 ± 17μm Re-implantation; p <0.01) with expected paracentral thinning following SMILE. Although in vivo confocal microscopy appeared to show higher reflectivity in all +4D treatment groups, there were minimal and inconsistent changes in inflammatory responses between modalities. SMILE and lenticule re-implantation may represent a safe and viable method for treating hyperopia, but further optimization for lower hyperopic treatments is warranted.

Two-years results of small-incision lenticule extraction and wavefront-guided laser in situ keratomileusis for Myopia

PURPOSE

To compare the 2-years visual and refractive outcomes between small-incision lenticule extraction (SMILE) and wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopia and myopic astigmatism.

METHODS

Our retrospective case-control study examined 30 eyes of 30 patients with the manifest refraction spherical equivalent (MRSE) of -3.71 ± 1.83 dioptres (D) who underwent SMILE and 30 eyes of 30 patients with MRSE of -3.81 ± 1.40 D who underwent wavefront-guided LASIK. We assessed the 2-years clinical outcomes.

RESULTS

Logarithm of the minimal angle of resolution (LogMAR)-corrected distance visual acuity (CDVA) was -0.23 ± 0.07 in the SMILE group and -0.24 ± 0.07 in the wavefront-guided LASIK group 2 years postoperatively (p = 0.82). Logarithm of the minimal angle of resolution-uncorrected distance visual acuity (UDVA) was -0.18 ± 0.09 and -0.15 ± 0.11 (p = 0.30, respectively). In the SMILE and wavefront-guided LASIK groups 2 years postoperatively, 100% and 73% of eyes, respectively, were within 0.5 D of the prompted MRSE correction (p = 0.005). Changes in the MRSE of -0.10 ± 0.30 D and -0.23 ± 0.51 D occurred from 3 months to 2 years (p = 0.40, respectively). We found a significant correlation between myopic regression and the changes in the keratometric readings from 3 months to 2 years after wavefront-guided LASIK (r = -0.48, p = 0.002), but not after SMILE (r = -0.004, p = 0.90).

CONCLUSION

Small-incision lenticule extraction offers better refractive outcomes than wavefront-guided LASIK during a 2-years follow-up for the correction of myopia and myopic astigmatism.

Interface healing and its correlation with visual recovery and quality of vision following small incision lenticule extraction

Purpose:

To study the time course of interface healing and its correlation with visual acuity, modulation transfer function (MTF), and aberrations after myopic small-incision lenticule extraction (SMILE) correction.

Methods:

Seventy-eight eyes of 78 patients (1 eye per patient) with a mean age of 25.7 years and mean spherical equivalent (SE) of −3.74D, undergoing bilateral SMILE procedure, were included in this study. On postoperative day 1, 2 weeks, and 3 months, dilated retroillumination photographs were taken and morphology of corneal interface was graded by comparing them with 5 standard templates representing 5 grades of interface roughness (IRG): IRG – 0 (clear), IRG – 1 (mild), IRG – 2 (moderate), IRG – 3 (severe), and IRG – 4 (severe IRG with Bowman's folds in visual axis). Pearson's correlations were computed to study correlation associations, and Wilcoxon signed-rank test was used for intragroup comparison of means. P ≤ 0.05 was considered statistically significant.

Results:

At 3 months, 90.70% eyes were Grade 0 while 9.30% eyes still had Grade 2 interface granularity. Mean IRG significantly improved from 2.47 ± 0.57 at day 1 to 0.62 ± 0.53 at 3 months (P = 0.00). At day 1, pre-SE showed a significant positive correlation with IRG; however, mean postoperative corrected distant visual acuity (CDVA, in decimal), corneal Strehl ratio (SR), and MTF showed weak but significant negative correlation with IRG (r² = 0.28 for SE, −0.052 for CDVA, −0.017 for SR, and −0.39 for MTF, respectively, P < 0.05 for all correlations). At 2 weeks and 3 months, corneal MTF continued to show a significant negative correlation, whereas other parameters did not show any correlation with IRG.

Conclusion:

Visual quality and corneal MTF may be significantly affected by the IRG in the immediate postoperative period after SMILE and may take 3 months or more for complete recovery.

[Refractive lenticule extraction - The ReLEx/SMILE technique : Video article]

Refractive lenticule extraction (ReLEx/SMILE) is a refractive surgical method developed by the authors in stages primarily for correction of myopia and myopic astigmatism, in which a femtosecond laser is exclusively used. In the (ReLEx/SMILE) method a refractive lenticule is generated by the femtosecond laser, which is subsequently extracted through a small incision. Opening of the corneal surface with a flap and use of an excimer laser is no longer necessary. In 2013 the method was newly assessed and classified by the Joint Commisssion for Refractive Surgery (KRC) of the Professional Association of Ophthalmologists (BVA) and the German Ophthalmological Society (DOG). This article presents the individual stages of the technique in a video and possible errors and their avoidance are explained.

Visual outcomes after balanced salt solution infiltration during lenticule separation in small-incision lenticule extraction for myopic astigmatism

To evaluate the refractive outcomes of balanced salt solution infiltration during small-incision lenticule extraction (SMILE).This randomized prospective study enrolled 52 patients (104 eyes) with myopic astigmatism. Patients underwent SMILE to correct the myopic astigmatism in Daping Hospital of the Third Military Medical University between January and July 2013. One eye of each patient received traditional SMILE (control group) and the other received a modified SMILE procedure (liquid infiltration group). The corrected distance visual acuity (CDVA), postoperative uncorrected distance visual acuity (UDVA), refraction, wavefront aberration, intraocular pressure (IOP), modulation transfer function (MTF) cut-off frequency, and objective scattering index (OSI) were evaluated.UDVA in the liquid infiltration group was significantly higher than that in the control group at 1 day postoperatively, but not at 1 month after surgery. Moreover, OSI and MTF cut-off frequency in the liquid infiltration group were higher than those in the control group at early follow-up. However, no significant intergroup difference was observed in the OSI and MTF cut-off frequency at 3 months after surgery. In addition, the predictability was better in the liquid infiltration group than in the control group. The changes of horizontal coma in the liquid infiltration group were lesser than those in the control group. However, no intergroup difference was observed in the reduction of IOP at 1 month after surgery.The modified SMILE procedure results in better visual outcomes than did the traditional SMILE procedure when used for treating myopic astigmatism.

Small Incision Lenticule Extraction for Correction of Myopia and Myopic Astigmatism: First 24-Hour Outcomes

Purpose

To observe the first 24-hour (h) outcomes of the small incision lenticule extraction procedure (SMILE) for myopia and myopic astigmatism.

Methods

Fifty-three eyes (27 patients) scheduled for SMILE were followed immediately (0 h), 2, 4, 6, and 24 h after SMILE. Uncorrected visual acuity (UCVA), conjunctival congestion, pain level, and corneal edema, thickness, and densitometry were recorded.

Results

At 2 h after SMILE, 15.1% of eyes had ≤0.1 LogMAR UCVA; this increased to 62.3%, 98.1%, and 100% at 4, 6, and 24 h, respectively. Some eyes (33.96%) had mild corneal edema immediately after surgery. No 6 h postoperative edema was observed. In the first 24 h after SMILE, corneal thickness gradually decreased. Postoperative corneal densitometry values were significantly higher than preoperative values but gradually decreased during the first postoperative 24 h.

Conclusions

In the first postoperative 24 h, UCVA and corneal status (edema and densitometry) improved quickly.

[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.

Refraction outcomes after suction loss during small-incision lenticule extraction (SMILE)

Purpose

To evaluate refractive outcomes of two management approaches after suction loss during the small-incision lenticule extraction (SMILE) technique.

Patients and methods

This retrospective and comparative study was conducted at the El-Gowhara Private Eye Center. It included 26 consecutive eyes of patients who experienced suction loss during the SMILE technique. Patients were divided into two groups by the technical difficulties in redocking: in group A (12 eyes) suction loss occurred after the posterior lenticular cut and the creation of side-cuts, then suction was reapplied, and the procedure was completed; in group B (14 eyes) suction loss occurred after the posterior lenticular cut and the creation of side-cuts, then the procedure was postponed for 24 hours and completed with the same parameters. Manifest refraction outcomes were measured and compared 6 months postoperatively.

Results

This study included 26 eyes with suction loss during the SMILE technique: five patients with suction loss in both eyes, nine patients with suction loss in the right eye and seven patients with suction loss in the left eye. The incidence of suction loss in this study was 2.7%. At the postoperative 6-month follow-up time, there were statistically significant differences in refraction outcomes between the two groups, with a hyperopic shift in group A compared with group B.

Conclusion

A good refraction outcome can be achieved with appropriate management of suction loss during the SMILE technique, and it is recommended to postpone the treatment if this happens.

Small-incision lenticule extraction versus femtosecond lenticule extraction for myopic: a systematic review and Meta-analysis

AIM

To examine differences in efficacy, accuracy, safety, aberrations and corneal biomechanical between Small incision lenticule extraction (SMILE) and femtosecond lenticule extraction (FLEx) for myopia.

METHODS

Comprehensive studies were conducted on the PubMed, MEDLINE, EMBASE, and Cochrane Controlled Trials Register before 31 July, 2015. Meta-analyses were performed on the primary outcomes [loss of ≥2 lines of corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA) ≥20/20, spherical equivalent (SE) within ±0.50 diopters (D), final refractive SE], secondary outcomes were high-order aberrations (HOAs) and corneal biomechanical [central corneal thickness (CCT), corneal hysteresis (CH) and corneal resistance factor (CRF)].

RESULTS

Seven trials describing a total of 320 eyes with myopia were included in this Meta-analysis. No significant differences were found in the efficacy [UDVA weighted mean difference (WMD) -0.01; 95%CI: -0.04 to 0.01; P=0.37, UDVA ≥20/20, OR 1.49; 95%CI: 0.78 to 2.86; P=0.23], accuracy (SE WMD -0.03; 95%CI: -0.12 to 0.07; P=0.58, SE within ±0.5 D OR 1.25; 95%CI: 0.34 to 4.65; P=0.74), HOAs (WMD -0.04; 95%CI: -0.09 to 0.01; P=0.14) and CCT WMD 1.83; 95%CI: -7.07 to 10.72; P=0.69, CH WMD -0.01; 95%CI: -0.42 to 0.40; P=0.97, CRF WMD 0.17; 95%CI: -0.33 to 0.67; P=0.50) in the last fellow-up. But for safety, FLEx may achieve fewer CDVA lost two or more two lines (OR 11.11; 95%CI: 1.27 to 96.86; P=0.03) than SMILE, however CDVA (WMD 0.00; 95%CI: -0.03 to 0.02; P=0.77) is similar.

CONCLUSION

SMILE and FLEx are comparable in terms of both efficacy, accuracy, aberrations and corneal biomechanical measures in the follow-up, but FLEx seems to be better in safety measures. The results should be interpreted cautiously since relevant evidence is still limited, although it is accumulating. Further large-scale, well-designed randomized controlled trials are urgently needed.

Vision-related quality of life and visual outcomes after small-incision lenticule extraction and laser in situ keratomileusis

PURPOSE

To compare vision-related quality of life (VRQoL) scores and clinical outcomes between small-incision lenticule extraction and laser in situ keratomileusis (LASIK).

SETTING

Singapore National Eye Centre, Singapore.

DESIGN

Prospective study.

METHODS

Patients had small-incision lenticule extraction using the Visumax 500 kHz femtosecond laser; or LASIK excimer ablation with the Wavelight Allegretto 400 Hz laser. Primary outcomes were 3-month predictability, efficacy, and safety. Secondary outcomes were intraoperative experience, visual symptoms, and VRQoL (validated Quality of Life Impact of Refractive Correction [QIRC] questionnaire) in 25 a subgroup of patients in each group. Following Rasch analysis, "Functional" and "Emotional," QIRC dimensions were analysed separately.

RESULTS

At 3 months, predictability (82.5% versus 85.3%, ±0.5 diopters attempted correction, P =.453), safety index (1.13 ± 0.19 [SD] versus 1.07 ± 0.16, P = .158), and efficacy index (0.91 ± 0.21 versus 0.97 ± 0.19; P = .002) were found when comparing small-incision lenticule extraction (172 eyes) and LASIK (matched 688 eyes). Intraoperative experience between groups was not statistically different; visual fluctuations (P = .020) and episodes of visual blurring (P = .008) were greater after small-incision lenticule extraction than after LASIK at 1 month but not at 3 months. There was no difference in "functional" (66.7 ± 15.7 versus 55.3 ± 22.2, P = .064) and "emotional" (42.7 ± 23.2 versus 37.9 ± 23.8, P = .394) QIRC dimensions between the 2 groups (25 patients in each group) at 3 months.

CONCLUSION

The study, 3-month predictability, safety, and VRQL scores were not statistically different between small-incision lenticule extraction and LASIK.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Efficacy, safety, predictability, aberrations and corneal biomechnical parameters after SMILE and FLEx: Meta-analysis

AIM

To identify possible differences of efficacy, safety, predictability, higher-order aberrations and corneal biomechnical parameters after small-incision lenticule extraction (SMILE) and femtosecond lenticule extraction (FLEx).

METHODS

A systematic literature retrieval was conducted in Medline, Embase and the Cochrane Library, up to October, 2015. The included studies were subject to a Meta-analysis. Comparison between SMILE and FLEx was measured as pooled odds ratio (OR) or weighted mean differences (WMD). Of 95% confidence intervals (CI) were used to analyze data.

RESULTS

A total of seven studies were included. Firstly, there were no differences in uncorrected distance visual acuity (UDVA) 20/20 or better (OR, 1.37; 95% CI, 0.69 to 2.69; P=0.37) and logMAR UDVA (WMD, -0.02; 95% CI, -0.05 to 0.01; P=0.17) after SMILE versus FLEx. We found no differences in corrected distance visual acuity (CDVA) unchanged (OR, 0.98; 95% CI, 0.46 to 2.11; P=0.97) and logMAR CDVA (WMD, -0.00; 95% CI, -0.01 to 0.01; P=0.90) either. Secondly, we found no differences in refraction within ±1.00 D (OR, 0.98; 95% CI, 0.13 to 7.28; P=0.99) and ±0.50 D (OR, 1.62; 95% CI, 0.62 to 4.28; P=0.33) of target postoperatively. Thirdly, for higher-order aberrations, we found no differences in the total higher-order aberrations (WMD, -0.04; 95% CI, -0.09 to 0.01; P=0.14), coma (WMD, -0.04; 95% CI, -0.09 to 0.01; P=0.11), spherical (WMD, 0.01; 95% CI, -0.02 to 0.03; P=0.60) and trefoil (WMD, -0.00; 95% CI, -0.04 to 0.03; P=0.76). Furthermore, for corneal biomechanical parameters, we also found no differences (WMD, 0.08; 95% CI, -0.17 to 0.33; P=0.54) after SMILE versus FLEx.

CONCLUSION

There are no statistically differences in efficacy, safety, predictability, higher-order aberrations and corneal biomechnical parameters postoperative between SMILE and FLEx.

Short term effects of small incision lenticule extraction surgery on corneal endothelium

AIM

To assess the effects of small incision lenticule extraction (SMILE) surgery on the corneal endothelium at 1d to 1mo postoperatively.

METHODS

A retrospective, observational study was conducted on 47 patients (47 eyes) who received SMILE surgery. Patients were grouped according to contact lens wear condition. The corneal endothelium was examined preoperatively and at 1d, 1wk and 1mo postoperatively. The corneal endothelium was analyzed for endothelial cell density (ECD), percentage of hexagonal cells, and coefficient of variation (CV) of cell size.

RESULTS

There were no significant decrease in the ECD, percentage of hexagonal cells or increase in CV at 1d, 1wk and 1mo postoperatively (P>0.05). However, there was a small increase of ECD by 2.88% in contact lens wearers (78.26±113.62 cell/mm(2), P<0.05).

CONCLUSION

SMILE has no significant adverse effects on the corneal ECD and morphology during 1mo follow-up time.

Small incision lenticule extraction (SMILE) in 2015

Small incision lenticule extraction (SMILE) represents a recent addition to the refractive surgeon's range of procedures. Although there remains a number of similarities to existing techniques in terms of patient selection and treatment parameters, consideration is required to optimise patient outcomes and satisfaction. Here, we review the selection criteria, contraindications, indications and existing published safety and efficacy outcomes.

SMILE Procedures With Four Different Cap Thicknesses for the Correction of Myopia and Myopic Astigmatism

PURPOSE

To study the feasibility of performing myopic femtosecond small incision lenticule extraction (SMILE) with four different cap thicknesses (130, 140, 150, and 160 μm).

METHODS

In this retrospective, comparative, non-randomized clinical trial, a refractive lenticule of intrastromal corneal tissue was cut with the VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Jena, Germany) using different depths of the non-refractive lenticule cut. Manifest refraction, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and Objective Scattering Index (OSI) were evaluated. Minimum follow-up time was 1 year.

RESULTS

Ninety-four eyes of 47 patients with myopia with (14 patients) and without (33 patients) astigmatism were treated. One year after the surgery, mean log-MAR UDVA, logMAR CDVA, SE, and OSI were 0.07 ± 0.12, 0.01 ± 0.37, 0.07 ± 0.57, and 0.88 ± 0.17, respectively (P < .05). There were no significant statistical differences in logMAR UDVA, logMAR CDVA, SE, or OSI (P > .05) variables when the different groups were compared for the same periods of time.

CONCLUSIONS

No differences in visual acuity, refractive outcomes in optical visual quality, or complications were observed when using SMILE at four different depths.

Contralateral Eye Comparison Between Femtosecond Small Incision Intrastromal Lenticule Extraction at Depths of 100 and 160 μm

PURPOSE

To compare the visual results, higher-order aberrations, and corneal biomechanical properties of femtosecond small incision lenticule extraction (SMILE) at depths of 100 and 160 μm.

METHODS

A prospective comparative interventional clinical trial of a series of patients who underwent SMILE. In the right eye, a refractive lenticule was created at a depth of 100 μm, and in the left eye, a depth of 160 μm was used. Manifest refraction, uncorrected visual acuity, total high-order aberrations (THOA), and corneal biomechanical properties of both eyes were evaluated 1 month postoperatively.

RESULTS

Thirty patients with bilaterally stable refractive errors were included in this study. One month postoperatively, mean corneal hysteresis was 9.71 ± 0.68 in the right eyes and 9.97 ± 0.77 in the left eyes, whereas the mean corneal resistant factor was 9.13 ± 1.04 and 9.31 ± 0.92 in the right and left eyes, respectively. Both corneal hysteresis and corneal resistant factor showed statistically significantly higher values in the left eyes (lenticule at a depth of 160 μm). No statistically significant differences were found between the right and the left eyes regarding manifest refraction, uncorrected visual acuity, and THOA.

CONCLUSIONS

Creating the refractive lenticule at a depth of 160 μm in SMILE had less effect on the corneal biomechanics than did creating a lenticule at a depth of 100 μm with no statistically significant differences in the refractive outcome and THOA between both groups.

Comparison of Early Changes in Ocular Surface and Inflammatory Mediators between Femtosecond Lenticule Extraction and Small-Incision Lenticule Extraction

Purpose

To evaluate the short-term changes in ocular surface measures and tear inflammatory mediators after femtosecond lenticule extraction (FLEx) and small-incision lenticule extraction (SMILE) procedures.

Methods

Eighteen subjects (18 eyes) underwent FLEx and 23 subjects (23 eyes) underwent SMILE in this single-center and prospective study. Central corneal sensitivity, Schirmer I test (SIT), noninvasive tear breakup time (NI-TBUT), tear meniscus height, corneal fluorescein (FL) staining, and ocular surface disease index (OSDI) were assessed in all patients. Concentrations of interleukin-1α (IL-1α), tumor necrosis factor-α (TNF-α), nerve growth factor (NGF), interferon-γ (IFN-γ), transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) in collected tears were measured by multiplex antibody microarray.

Results

Central corneal sensitivity was reduced in both groups, but the scores in the SMILE group were higher than those in the FLEx group at all time points postoperatively (P<0.01). Lower FL scores and longer NI-BUT were observed in the SMILE group 1 week after surgery (P<0.05). OSDI scores in both groups increased rapidly at 1 day and 1 week postoperatively, then returned to their preoperative levels within 1 month (P<0.05). There were no significant differences in SIT or tear meniscus height between the two groups. Lower and faster recovery of tear NGF, TGF-β1 and IL-1α concentration were found in the SMILE group compared to the FLEx group postoperatively. No significant difference was found in tear TNF-α, IFN-γ and MMP-9 for either group before or after surgery. Tear NGF, TGF-β1 and IL-1α show a correlation with ocular surface changes after FLEx or SMILE surgery.

Conclusion

SMILE has superiority over FLEx in early ocular surface changes and NGF, TGF-β1 and IL-1α may contribute to the process of ocular surface recovery.

Trial Registration

ClinicalTrials.gov NCT02540785

Posterior Corneal Elevation after Small Incision Lenticule Extraction for Moderate and High Myopia

Purpose

To investigate the changes of posterior corneal elevation after small incision lenticule extraction (SMILE) for moderate and high myopia.

Methods

In this prospective study, fifty consecutive eyes of thirty patients (10 male, 20 female) who underwent SMILE for myopia and myopic astigmatism were included. Eyes were divided in two groups based on the preoperative spherical equivalent refraction: high myopia group (32 eyes, range -6.25D to -10.00D) and moderate myopia group (18 eyes, range -3.00D to -6.00D). Posterior corneal surfaces were measured by a Scheimpflug camera (Pentacam, Oculus Germany) preoperatively and 1 month, 3 months, 6 months and 12 months postoperatively. Posterior central elevation (PCE) and posterior mean elevation (PME) at 17 predetermined points in the central-4mm area above the best-fit sphere were analyzed.

Results

No significant difference in the amount of posterior corneal elevation changes in the high myopia group was noted over time (P = 0.23 and P = 0.94 for PCE and PME, respectively). Similarly, the changes in the moderate myopia group before and after SMILE were not significant either (P = 0.34 and P = 0.40 for PCE and PME). A statistically significant correlation was found between the residual bed thickness and the shift of the PCE in the high myopia group at 12 months postoperatively (r = 0.53, P = 0.01).

Conclusions

The results of this study suggest that the posterior corneal surface remain stable within one year after SMILE for both moderate and high myopia. The changes of PCE correlate to the residual bed thickness for high myopia. Long-term changes of posterior corneal surface need further investigation.

Ultrastructural Changes and Corneal Wound Healing After SMILE and PRK Procedures

PURPOSE

To compare keratocyte activation, cellular morphologic changes and wound healing after SMILE and PRK procedures using transmission electron microscope (TEM).

METHODS

In this study, 22 New Zealand white rabbits (10- to 15-week old) were used. The right eyes of all animals underwent SMILE procedure and the left eyes underwent PRK procedure. Cornea samples taken 1 day and 1 week postoperatively were examined using TEM.

RESULTS

Using TEM 1 day after SMILE procedure, the organization of collagen fibers seemed to have been preserved without thermal alterations. Keratocyte activation was observed in the anterior stroma. Disrupted collagen arrangement and debris of cells are visible in the area of damage, and some phagocytic cells and a large number of secondary lysosomes are visible in those cells. At the perimeter zone of the interface, many coenocytes and collagen fragments could be found within the phagocytic cell. One week after SMILE procedure, potential lacuna could be discerned. A large part of the interface of the lenticule extracted had an appearance of clearly being adhered to some mucus secretions. One day after PRK procedure, an irregular epithelial surface was visible using TEM. Keratocytes had been activated and the rough endoplasmic reticulum in those cells had expanded. One week after PRK procedure, the epithelial surface still was irregular and keratinization of the epithelium was still visible in some areas. Corneal endothelium cells were mildly damaged and some vacuoles within the cytoplasm could be discerned. In the anterior stroma, some unhealthy activated keratocytes could still be observed. New collagen fibrils were found present near the activated keratocytes.

CONCLUSION

Using TEM, keratocyte activation could still be observed after SMILE compared to after PRK procedure. Fewer cellular ultrastructural changes were seen after SMILE procedure. Unlike in PRK procedure, no damaged epithelium and endothelium were found after SMILE.

Corneal tissue interactions of a new 345 nm ultraviolet femtosecond laser

PURPOSE

To assess the suitability of a new 345 nm ultraviolet (UV) femtosecond laser for refractive surgery.

SETTING

Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany.

DESIGN

Experimental study.

METHODS

Twenty-five porcine corneas were used for stromal flap or lamellar bed creation (stromal depth, 150 μm) and 15 rabbit corneas for lamellar bed creation near the endothelium. Ultraviolet femtosecond laser cutting-line morphology, gas formation, and keratocyte death rate were evaluated using light and electron microscopy and compared with a standard infrared (IR) femtosecond laser. Endothelial cell survival was examined after application of a laser cut near the endothelium.

RESULTS

Flaps created by the UV laser were lifted easily. Gas formation was reduced 4.2-fold compared with the IR laser (P = .001). The keratocyte death rate near the interface was almost doubled; however, the death zone was confined to a region within 38 μm ± 10 (SD) along the cutting line. Histologically and ultrastructurally, a distinct and continuous cutting line was not found after UV femtosecond laser application if flap lifting was omitted and standard energy parameters were used. Instead, a regular pattern of vertical striations, presumably representing self-focusing induced regions of optical tissue breakdown, were identified. Lamellar bed creation with standard energy parameters 50 μm from the endothelium rendered the endothelial cells intact and viable.

CONCLUSION

The new 345 nm femtosecond laser is a candidate for pending in vivo trials and future high-precision flap creation, intrastromal lenticule extraction, and ultrathin Descemet-stripping endothelial keratoplasty.

FINANCIAL DISCLOSURES

Mr. Klenke and Ms. Skerl were paid employees of Wavelight GmbH when the study was performed. Dr. Seiler is a scientific consultant to Wavelight GmbH. No other author has a financial or proprietary interest in any material or method mentioned.

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.

Treatment of corneal perforation with lenticules from small incision lenticule extraction surgery: a preliminary study of 6 patients

PURPOSE

To evaluate the use of lenticules extracted using small incision lenticule extraction (SMILE) surgery as a surgical alternative for wound closure in corneal perforation.

METHODS

Corneal lenticules obtained through SMILE surgery with central thickness >100 μm were fixed over corneal perforation sites using 10-0 nylon interrupted stitches. Patients were monitored for a minimum of 1 year and were assessed using slit-lamp microscopy, fluorescein, digital tonometry, and best spectacle-corrected visual acuity (BSCVA) measurements. Postoperative complications throughout the study period were recorded.

RESULTS

Corneal perforations were successfully sealed in all 6 patients; 3 patients (50%) exhibited improved postoperative BSCVA. Between 3 and 4 weeks after the operation, part of the lenticules became incorporated into the corneal stroma and complete reepithelialization was achieved. During the follow-up period of 12 months, no evidence of infection, relapse, or perforation was detected in any patient.

CONCLUSIONS

These preliminary findings suggest that the use of corneal lenticules may be a safe and effective surgical alternative for corneal perforation closure, with potential clinical application as relatively simple and inexpensive temporary measures to improve the condition of the cornea for further definitive interventions.

Postoperative ocular higher-order aberrations and contrast sensitivity: femtosecond lenticule extraction versus pseudo small-incision lenticule extraction

PURPOSE

To evaluate and compare changes in contrast sensitivity and ocular higher-order aberrations (HOAs) after femtosecond lenticule extraction (FLEx) and pseudo small-incision lenticule extraction (SMILE).

SETTING

Singapore National Eye Centre, Singapore.

DESIGN

Retrospective case series.

METHOD

Patients had femtosecond lenticule extraction (Group 1) or pseudo small-incision lenticule extraction (Group 2) between March 2010 and December 2011. The main outcome measures were manifest refraction, HOAs, and contrast sensitivity 1, 3, 6, and 12 months postoperatively.

RESULTS

Fifty-two consecutive patients (102 eyes) were recruited, 21 patients (42 eyes) in Group 1 and the 31 patients (60 eyes) in Group 2. The uncorrected and corrected distance visual acuities were significantly better in Group 2 than in Group 1 at 12 months (P = .032). There was no significant increase in 3rd- or 4th-order aberrations at 1 year and no significant difference between the 2 groups preoperatively or postoperatively. At 1 year, there was a significant increase in mesopic contrast sensitivity in Group 2 at 1.5 cycles per degree (cpd) (P = .008) that was not found in Group 1, and photopic contrast sensitivity at 6.0 cpd was higher in Group 2 (P = .027).

CONCLUSIONS

These results indicate that refractive lenticule extraction is safe and effective with no significant induction of HOAs or deterioration in contrast sensitivity at 1 year. Induction of HOAs was not significantly different between both variants of refractive lenticule extraction. However, there was significant improvement in photopic contrast sensitivity after pseudo small-incision lenticule extraction, which persisted through 1 year.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Evaluation of a 345 nm Femtosecond Laser for Corneal Surgery with Respect to Intraocular Radiation Hazard

PURPOSE

We report our findings from a preclinical safety study designed to assess potential side effects of corneal ultraviolet femtosecond laser treatment on lens and retina.

METHODS

Refractive lenticules (-5 dpt) with a diameter of 6 mm were created in the right cornea of eight Dutch Belted rabbits. Radiant exposure was 0.5 J/cm² in two animals and 18 J/cm² in six animals. The presence of lens opacities was assessed prior to and up to six months following laser application using Scheimpflug images (Pentacam, Oculus) and backscatter analysis (Opacity Lensmeter 702, Interzeag). Ganzfeld flash and flicker electroretinogram (ERG) recordings were obtained from both eyes prior to and up to six weeks following laser application. At the study endpoint, retinas were examined by light microscopy.

RESULTS

Independent of energy dose applied, no cataract formation could be observed clinically or with either of the two objective methods used. No changes in ERG recordings over time and no difference between treated and untreated eye were detected. Histologically, retinal morphology was preserved and retinal pigment epithelium as well as photoreceptor inner and outer segments appeared undamaged. Quantitative digital image analysis did not reveal cell loss in inner or outer nuclear layers.

CONCLUSIONS

Our analysis confirms theoretical considerations suggesting that ultraviolet femtosecond laser treatment of the cornea is safe for intraocular tissues. Transmitted light including stray light induces no photochemical effects in lens or retina at energy levels much higher than required for the clinical purpose. These conclusions cannot be applied to eyes with pre-existing retinal damage, as these may be more vulnerable to light.

Refractive lenticule extraction: transition and comparison of 3 surgical techniques

PURPOSE

To describe the transition and outcomes of 3 refractive lenticule extraction (ReLEx) techniques: femtosecond lenticule extraction (FLEx), small-incision lenticule extraction (SMILE), and pseudo small-incision lenticule extraction.

SETTING

Singapore National Eye Center, Singapore.

DESIGN

Prospective comparative case series.

METHODS

Refractive lenticule extraction was performed between March 1, 2010, and November 1, 2012, using the Visumax 500 kHz femtosecond laser system. The main outcome measures were the refractive efficacy, predictability, and safety over 12 months.

RESULTS

The study enrolled 88 eyes. All 3 refractive lenticule extraction techniques yielded good refractive outcomes and stability over 12 months. Three months postoperatively, the mean overall efficacy index of refractive lenticule extraction was 0.89±0.22 (SD), with 95.5% of eyes attaining an uncorrected distance visual acuity (UDVA) of better than 20/40 and 60.2% of better than 20/20. Of all eyes, 95.5% were within ±1.00 diopter (D) and 78.4% within ±0.50 D of the attempted correction. The mean overall safety index was 1.06±0.17. At 3 months, all small-incision lenticule extraction eyes and 96.7% of pseudo small-incision lenticule extraction eyes had a UDVA of 20/40 or better, while femtosecond lenticule extraction eyes had a lower efficacy index (87.0%). However, efficacy was comparable in all 3 groups by 12 months (mean 0.87±0.04 [standard error of the mean]; P=1.00).

CONCLUSION

The efficacy, safety, and predictability profiles of the 3 refractive lenticule extraction techniques were good over a 12-month follow-up.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

The evolution of corneal and refractive surgery with the femtosecond laser

The use of femtosecond lasers has created an evolution in modern corneal and refractive surgery. With accuracy, safety, and repeatability, eye surgeons can utilize the femtosecond laser in almost all anterior refractive procedures; laser in situ keratomileusis (LASIK), small incision lenticule extraction (SMILE), penetrating keratoplasty (PKP), insertion of intracorneal ring segments, anterior and posterior lamellar keratoplasty (Deep anterior lamellar keratoplasty (DALK) and Descemet's stripping endothelial keratoplasty (DSEK)), insertion of corneal inlays and cataract surgery. As the technology matures, it will push surgical limits and open new avenues for ophthalmic intervention in areas not yet explored. As we witness the transition from femto-LASIK to femto-cataract surgery it becomes obvious that this innovation is here to stay. This article presents some of the most relevant advances of femtosecond lasers to modern corneal and refractive surgery.

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.