Comparison of myopic astigmatic correction after cross-assisted SMILE, FS-LASIK, and transPRK

PURPOSE

To compare astigmatic correction among cross-assisted small-incision lenticule extraction (SMILE), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and transepithelial photorefractive keratectomy (transPRK).

SETTING

The Eye Hospital of Wenzhou Medical University, Zhejiang, China.

DESIGN

Prospective comparison study.

METHODS

154 right eyes of 154 patients with astigmatism of -1.00 to -2.75 diopters (D) were included in this study. 64 eyes, 42 eyes, and 48 eyes were receiving SMILE, FS-LASIK, and transPRK, respectively. The SMILE group used cross-axial alignment for head positioning for astigmatism correction. In the FS-LASIK and transPRK groups, static and dynamic cyclotorsion control were used. Changes in ocular parameters and vector analysis were assessed at 6 months postoperatively.

RESULTS

The safety and efficacy indices were comparable among the 3 groups at 6 months postoperatively. Residual astigmatism was smallest in the SMILE group (-0.23 ± 0.25 D) compared with that in FS-LASIK (-0.40 ± 0.28 D, P = .009) and transPRK groups (-0.42 ± 0.32 D, P = .001). 53 (82.8%), 36 (85.7%), and 37 (77.1%) eyes achieved an angle of error within ±5 degrees, respectively ( P = .55). Notably, vector analysis showed that the difference vector, the magnitude of the error, and its absolute value were significantly smaller in the SMILE group than those in the other groups ( P < .05). In addition, the higher-order aberrations, especially coma, were significantly induced postoperatively in each group ( P < .001).

CONCLUSIONS

Residual astigmatism magnitude was smallest by cross-assisted SMILE, followed by FS-LASIK and transPRK, and the astigmatism axial correction was comparable among groups.

The effect of different angle kappa on higher-order aberrations after small incision lenticule extraction

This study aimed to compare higher-order aberrations (HOAs) after small incision lenticule extraction (SMILE) in patients with different angle kappa. This is a retrospective report in which 341 right eyes of 341 patients who were subjected to SMILE, which used coaxially sighted corneal light reflex (CSCLR) as the treatment zone centered, treated by the same experienced surgeon (LHB) for correction of myopia and myopic astigmatism, preoperative and postoperative spherical equivalent (SE), angle kappa, total higher-order aberrations (total HOA), spherical aberration (SA), vertical coma (VC), horizontal coma (HC), oblique trefoil (OT), and horizontal trefoil (HT), were compared. SMILE showed outstanding performance in terms of safety, efficacy, and predictability. In addition, a comparison of preoperative and postoperative HOAs exhibited the difference of total HOA (P < 0.01), SA (P < 0.01), VC (P < 0.01), and HC (P < 0.01), which was statistically significant; however, for OT and HT with the longer follow-up time, the statistical difference gradually decreased. For stratification of angle kappa into groups based on decantation, angle kappa was divided into three major groups: r < 0.1 mm, 0.1 ≤ r < 0.2 mm, and r ≥ 0.2 mm; the changes of SA (F = 4.127, P = 0.021) and OT (F = 3.687, P = 0.031) exhibited significant difference after 1 year of SMILE. We performed a correlation analysis of all preoperative and postoperative parameters, and the results indicated that the preoperative total HOA was negatively correlated with preoperative cylindrical diopter (DC), and postoperative total HOA, SA, and coma were affected by spherical diopter (DS) and SE. Moreover, we also found a significant difference of SA and VC in the early postoperative with preoperative. SA was positively correlated with Y values and r of 1 year after SMILE. All of the analyzed parameters in the three groups, except for the trefoil, gradually increased over time; however, the trefoil could gradually stabilize over time. We also divided angle kappa into four groups by quadrants; the result showed that the effects of higher-order aberrations were markedly different from the various quadrants. Patients with large angle kappa were able to increase VC and SA postoperatively, and higher HOAs were more significant in patients with high myopia. The differences in quadrants exhibited a diversity of HOAs; this could be attributed to the corneal surface reestablishment and the alteration of angle kappa, but the trend was not apparent. Although all patients displayed increased HOAs after SMILE, the potential application of CSCLR as the treatment zone centered still showed excellent safety, efficacy, and predictability.

Comparison of the Clinical Effectiveness of Correcting Different Types of Astigmatism with Small Incision Lenticule Extraction

Few studies have reported the differential outcomes of Small Incision Lenticule Extraction (SMILE) on myopic astigmatism. Given this, we examined the effectiveness of SMILE for up to one year, comparing with-the-rule (WTR), against-the-rule (ATR), and oblique astigmatism, conducting a retrospective review of patients who underwent correction of myopic astigmatism using the 500-kHz VisuMax femtosecond laser (Carl Zeiss Meditec) at two refractive clinics in Poland between 2016-2017. Patients were aged ≥21 with stable refractive errors between -0.5 and -10.0 diopter (D) with astigmatism up to 5D. The mean age of the 209 patients (355 eyes) available was 32 years; 58.4% were female. Of these, 247 had WTR, 62 oblique, and 46 ATR astigmatism. The mean pre-operative spherical equivalent (SE) was -5.4 ± 2.57D and the cylinder -1.7 ± 1.0D. The mean SE for WTR reduced from -5.60 ± 2.37D to -0.31 ± 0.67D at 2 months and -0.38 ± 0.70D at 12 months; the mean cylinder improved from -1.90 ± 1.10D to -0.31 ± 0.39D and -0.36 ± 0.43D, respectively. Eyes with oblique astigmatism also improved from a mean SE of -5.8 ± 3.4 D to -0.82 ± 1.50D and -0.69 ± 1.15D and a cylinder of -1.4 ± 0.73D to -0.17 ± 0.33D at 2 months and -0.1 ± 0.32D at 12. For ATR, the mean SE improved from -4.0 ± 1.8D to -0.08 ± 0.22D and -0.04 ± 0.12D; and the mean cylinder from -1.25 ± 0.53 to -0.02 ± 0.09D -0.08 ± 0.21D at 2 and 12 months, respectively. There were statistically significant improvements in SE, manifest sphere and cylinder refraction, and UDVA and CDVA scores for each cylinder type at 2 months with ATR cylinders having better outcomes. Although missing data limited interpretation at one year, differences were maintained. The magnitude of error calculations suggests that WTR was more prone to under-correction, particularly for high astigmatism (>1.5D). SMILE for myopic astigmatism reliably corrects SE, irrespective of the subtype of astigmatism.

Vector analysis of astigmatism correction after PRK, FS-LASIK, and SMILE for myopic astigmatism

PURPOSE

To compare astigmatic correction among photorefractive keratectomy (PRK), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and small-incision lenticule extraction (SMILE).

METHODS

This prospective study enrolled 157 eyes that underwent three procedures (59 PRK, 47 FS-LASIK, and 51 SMILE) for the treatment of myopia with low to high astigmatism (- 0.25 to - 4.50 D). Ocular residual astigmatism (ORA) was calculated by vector analysis using refractive (RA) and corneal astigmatism. Vector analysis results were compared in different procedures in the two RA groups (low ≤ 1.00 D and high > 1.00 D) at 3 and 12 months postoperatively.

RESULTS

There were no significant between-group differences in postoperative safety and efficacy outcomes (all P > 0.05). No significant differences were found in postoperative cylinders between all surgical groups (all p > 0.05), except for 3 months postoperative ORA in FS-LASIK (P = 0.004). At 12 months, 77%, 59.2%, and 50% of eyes attain emmetropia in the FS-LASIK, SMILE, and PRK groups, respectively. Vector analysis showed comparable values for surgical induced astigmatism, target induced astigmatism, mean error, and angle of error between groups at 12 months. Significant differences were observed only in the correction index and difference vector parameters in the astigmatic > 1.00 D group at 3 months (P < 0.001), and FS-LASIK was preferable.

CONCLUSIONS

One-year outcomes revealed that PRK, FS-LASIK, and SMILE were all equally effective in correcting myopic astigmatism. However, FS-LASIK demonstrated more favorable astigmatism correction in eyes with astigmatism > 1.00D in early postoperatively.

Relationship between postoperative residual refractive error and preoperative corneal stiffness in small-incision lenticule extraction

PURPOSE

To explore the relationship between postoperative residual refractive error and preoperative corneal stiffness after small-incision lenticule extraction (SMILE).

SETTING

Hospital clinic.

DESIGN

Retrospective cohort study.

METHODS

Corneal stiffness was evaluated using the stress-strain index (SSI). Associations between postoperative spherical equivalent (SE) and corneal stiffness were determined using longitudinal regression analysis after adjustment for sex, age, preoperative SE, and other variables. The cohort was divided into halves to compare risk ratios for residual refraction in corneas with different SSI values. Low SSI values were defined as having less-stiff corneas and others as having stiffer corneas.

RESULTS

287 patients (287 eyes) were included. Greater undercorrection was found in less-stiff corneas across all follow-up timepoints (less-stiff corneas: 1 day: -0.36 ± 0.45 diopters [D], 1 month: -0.22 ± 0.36 D, and 3 months: -0.13 ± 0.15 D; stiffer corneas: -0.22 ± 0.37 D, -0.14 ± 0.35 D, and -0.05 ± 0.11 D, respectively). Postoperative refraction exhibited a mean 0.05 D undercorrection for every 0.1-unit decrease in the SSI after adjustment for variables. The SSI accounted for nearly 10% of the variance in refractive outcomes. Less-stiff corneas increased the risk ratio of postoperative absolute SE >0 D and ≥0.25 D by 2.242 (95% CI, 1.334-3.768) and 3.023 (95% CI, 1.466-6.233), respectively, compared with stiffer corneas.

CONCLUSIONS

Postoperative residual refractive error was associated with preoperative corneal stiffness. Patients with less-stiff corneas had a 2- to 3-fold increased risk of residual refractive error after SMILE. Preoperative analysis of corneal stiffness can help modify nomogram algorithms of surgery and improve the predictability of refractive outcomes.

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.

Comparison of objective and subjective visual quality after flapless laser vision correction for mild to moderate myopia: SMILE vs PRK

PURPOSE

To investigate the differences in surgical results and the objective and subjective quality of vision (QoV) of patients after small incision lenticule extraction (SMILE) versus alcohol-assisted photorefractive keratectomy (PRK).

METHODS

Medical records of patients treated with SMILE and PRK were retrospectively examined. Visual quality, biometric parameters, Strehl ratio (SR), and corneal higher-order aberrations (HOAs) within a 6.0 mm area were recorded. The effective optical zone (EOZ) and decentration were measured using a tangential pre-post operation difference map. Subjective QoV and operation satisfaction were evaluated 6 months postoperatively using the Quality of Vision questionnaire.

RESULTS

The study comprised 100 eyes treated with SMILE (preoperative mean spherical equivalent (SE), - 4.52 ± 0.81 dioptres (D)) and 69 eyes with PRK (mean SE, - 4.21 ± 1.25 D). Six months postoperatively, the EOZ reduction was significantly larger in the PRK group (P < 0.001). Decentrations were comparable between the groups. Regarding visual symptoms, monocular diplopia was more common following PRK (P = 0.02), and 98 (98.00%) SMILE-treated and 67 (97.10%) PRK-treated patients were satisfied with the QoV. Both groups demonstrated significant increases in total HOAs, coma, and spherical aberration (SA) at 6 months postoperatively compared to preoperatively (P < 0.001); these values were significantly higher in the PRK (P < 0.05) compared to the SMILE group. SR increased significantly only in the PRK group (P < 0.05).

CONCLUSION

Although EOZ was more consistent with anticipated treatment and HOAs were fewer in SMILE, high patient-reported satisfaction and good corneal optical quality were achieved in both groups, indicating that both SMILE and alcohol-assisted PRK are excellent options for mild to moderate myopia correction.

Long-term visual quality after small incision lenticule extraction (SMILE) and laser assisted subepithelial keratomileusis (LASEK) for low myopia

Background

Few studies have reported the visual outcomes of small-incision lenticule extraction (SMILE) and laser-assisted subepithelial keratomileusis (LASEK) for myopia correction. This study aims to compare the visual quality and corneal wavefront aberrations after SMILE and LASEK for low-myopia correction.

Methods

In this prospective study, we included 29 eyes of 29 patients who received SMILE and 23 eyes of 23 patients who received LASEK between June 2018 and January 2019. The following measurements were assessed: uncorrected (UDVA) and corrected (CDVA) distance visual acuity, manifest refraction, corneal wavefront aberrations, and subjective visual quality. All patients were followed up for two years.

Results

All procedures were uneventful. An efficacy index of 1.19 ± 0.17 was established in the SMILE group and 1.23 ± 0.20 in the LASEK group. No eyes lost more than two lines of CDVA. We found that 93% (27/29) of the treated eyes in the SMILE group and 91% (21/23) in the LASEK group had spherical equivalent (SE) within ± 0.25D. The increases in the total corneal spherical aberration and the corneal front spherical aberration were lower in the SMILE group than in the LASEK group (P < 0.01). In contrast, the increases in the total corneal vertical coma and the corneal front vertical coma in the SMILE group were greater than those in the LASEK group (P < 0.01).

Conclusion

Both SMILE and LASEK have good safety, stability, and patient-reported satisfaction for low myopia. SMILE induced less corneal spherical aberration but greater vertical coma than LASEK.

SMILE for the Treatment of Residual Refractive Error After Cataract Surgery

INTRODUCTION

In the context of managing patients' expectations and satisfaction regarding visual acuity after cataract surgery, we aimed to investigate the improvement in visual acuity and patient satisfaction after small-incision lenticule extraction (SMILE) in pseudophakic (trifocal intraocular lens, IOL) patients with residual myopic refraction after cataract surgery.

METHODS

Seventy-six patients (82 eyes) who underwent cataract surgery with ZEISS AT LISA tri 839MP IOL implantation were included in this retrospective study. The included patients were 56-79 years old, wanted spectacle independence, and had preoperative myopic refraction between - 1.0 and - 2.25 diopters (D) and astigmatism between - 0.75 and - 1.75 D. The treatment status of these patients was defined as trifocal IOL (n = 82). SMILE was performed in patients who were dissatisfied after cataract surgery, and these patients were followed up for 1 year on average. We evaluated visual acuity and satisfaction and further examined laser vision correction and satisfaction levels in patients who were dissatisfied after trifocal IOL implantation.

RESULTS

The possible reasons for patient dissatisfaction were reading books, using a computer, and driving at night. After SMILE, the residual myopic refractive error (spherical) decreased significantly from - 2.08 ± 0.28 [- 2.25 to - 1.0] preoperatively to - 0.25 ± 0.20 - 0.5 to 0] 1 year postoperatively (p < 0.001). Additionally, the uncorrected distance visual acuity increased from 0.65 ± 0.08 [0.52-0.7] logMAR preoperatively to 0.09 ± 0.02 [0.05-0.1] logMAR at 1 month postoperatively (p < 0.001), 0.09 ± 0.02 [0.05-0.1] logMAR at 6 months postoperatively, and 0.06 ± 0.02 [0.05-0.1] logMAR at 12 months postoperatively (p < 0.001). Patient satisfaction measures after SMILE (reading, night driving, and using a computer) were significantly improved.

CONCLUSION

SMILE is a reliable method for treating residual refraction after cataract surgery, as it provides results in the shortest time without complications and increases patient satisfaction.

TRIAL REGISTRATION

The protocol was registered on clinicaltrials.gov (NCT04693663).

Fresh Human Myopic Lenticule Intrastromal Implantation for Keratoconus Using SMILE Surgery in a Long-term Follow-up Study: Ultrastructural Analysis by Transmission Electron Microscopy

PURPOSE

To investigate new intrastromal histological structures that develop after myopic human lenticular implantation in keratoconus with femtosecond laser-assisted small incision lenticule extraction (SMILE) surgery using transmission electron microscopy.

METHODS

Sixty eyes with advanced keratoconus indicated for corneal transplantation were included in this study. Fresh myopic lenticular implants were placed in all eyes through SMILE surgery. Lenticular implants were extracted from patients with myopic refractive errors of the cornea, untreated keratoconus, and treated keratoconus following 1, 2, and 3 years of surgery. These five lenticular samples were examined under the electron microscope and compared.

RESULTS

Disorganized and thinned collagen fibers were observed in the stroma with degenerative stromal cells (telocyte-like cells and keratocytes) in the keratoconic cornea. Apoptotic bodies and cell debris were easily observed near the disorganized fibers. In contrast, the myopic refractive error of the control and treatment groups demonstrated well-organized parallel lamellar structures. Healthy keratocytes and telocyte-like cells were observed in samples obtained 1, 2, and 3 years after lenticular implantation. Thus, telocyte-like cells may be activated by appropriate stimuli, such as stem cells, and be involved in stromal regeneration.

CONCLUSIONS

Fresh myopic intrastromal lenticular implantation is a safe, economical, and reliable technique that leads to increased corneal thickness, improved visual acuity, and the regeneration of healthy keratocytes and telocyte-like cells that are involved in stromal regeneration. [J Refract Surg. 2022;38(8):520-528.].

Objective and Subjective Quality of Vision After SMILE for High Myopia and Astigmatism

PURPOSE

To report subjective and objective quality of vision (QoV) results for high myopic small incision lenticule extraction (SMILE) between -9.00 and -13.00 diopters (D).

METHODS

This was a prospective study recruiting 114 patients undergoing SMILE with attempted spherical equivalent refraction (SEQ) correction from -9.00 to -13.00 D, and cylinder up to 5.00 D. Patients were informed before surgery of the increased risk of QoV symptoms. Patients completed the Rasch validated QoV questionnaire. Objective QoV was assessed by corneal and whole eye aberrations, HD Analyzer Objective Scatter Index (OSI) (Keeler), and contrast sensitivity. Patient satisfaction was assessed on a scale from 0 (very dissatisfied) to 10 (very satisfied). Individual item and total Rasch-scaled scores for the three subscales (frequency, severity, and bothersomeness) of the QoV questionnaire were calculated before and 12 months after surgery.

RESULTS

The mean patient satisfaction score was 9.27 ± 1.18 (range: 2 to 10), 8 or higher in 93%, and 7 or higher in 98% of patients. One patient with a satisfaction score of 2 had a simple refractive error re-treatment and then reported a satisfaction score of 10. The total mean ± standard deviation Rasch-scaled QoV score for the frequency, severity, and bothersomeness subscales before surgery was 24 ± 19, 20 ± 16, and 19 ± 18, respectively. Scores increased after surgery to 41 ± 18, 32 ± 16, and 30 ± 21, respectively (P < .001). Corneal aberrations (6 mm, OSI) increased on average by 0.39 µm for spherical aberration, 0.41 µm for coma, and 0.56 µm for higher order aberrations root mean square. OSI increased on average by 0.58. There was a small but statistically significant improvement in contrast sensitivity at 3, 6, 12, and 18 cycles per degree. There were no statistically significant correlations found between subjective scores for starbursts and objective measurements.

CONCLUSIONS

Satisfaction was high following SMILE for high myopia. As expected, there was an increase in QoV symptoms, mainly glare and starbursts. The acceptance of QoV symptoms for high myopic SMILE was high, indicating that residual refractive error and visual acuity are the major drivers for patient satisfaction with appropriate preoperative informed consent. [J Refract Surg. 2022;38(7):404-413.].

Two-Year Visual Outcomes of Evolution Implantable Collamer Lens and Small Incision Lenticule Extraction for the Correction of Low Myopia

Purpose

To investigate the 2-year visual quality of Evolution Implantable Collamer Lens (EVO-ICL) and small incision lenticule extraction (SMILE) for the correction of low myopia.

Methods

In this prospective study, we included 25 eyes of 25 patients (7 men) who underwent EVO-ICL and 36 eyes of 36 patients (16 men) who underwent SMILE between January 2018 and December 2018. Subjective and objective visual outcomes were compared between ICL and SMILE. All patients were followed for 2 years.

Results

At the postoperative 2-year visit, the percentage of patients with uncorrected distance visual acuity (UDVA) greater than or equal to preoperative corrected distance visual acuity (CDVA) was comparable in the ICL group (80%, 20/25) and SMILE group (88.89%, 32/36). Spherical equivalent (SE) was within ± 0.50 D in 96% (24/25) of the ICL group and 94.44% (34/36) of the SMILE group. No eyes lost more than 2 lines of CDVA. Postoperative high-order aberrations (HOAs) were significantly increased in the ICL group (p < 0.01) and in the SMILE group (p < 0.01). The most common visual complaint was halo after ICL and starburst after SMILE. There was no correlation between HOAs and visual complaints (p > 0.05).

Conclusion

Evolution Implantable Collamer Lens provides comparable safety, efficacy, long-term visual stability, and high patient satisfaction when compared to SMILE in correcting low myopia. EVO-ICL could be a favorable alternative for low myopia.

Key messages What was known?

What this paper adds?

Comparison of visual outcomes between 120-µm and 140-µm cap thicknesses 12 months after small incision lenticule extraction

To compare visual and refractive outcomes as well as changes in high-order aberrations in patients with 120- versus 140-µm cap thicknesses 12 months after small incision lenticule extraction. Ninety-four patients were randomized to receive small incision lenticule extraction with either a 120-µm cap thickness (n = 47) or a 140-µm cap thickness (n = 47) to treat myopia or myopic astigmatism, if not both. In an analysis of right eyes only during the 12-month follow-up period, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive outcomes, and high-order aberrations were evaluated. The distribution of patients by age and sex between the groups did not differ significantly (P = .803 and P = .680, respectively). CDVA, spherical and cylindrical refraction, and changes in total high-order aberration, spherical aberration, coma, and trefoil were similar between the groups at 6 and 12 months, postoperatively. However, UDVA was statistically significantly higher in patients with 140-μm cap thicknesses than with 120-μm cap thicknesses at 6 and 12 months postoperatively (P < .001 and P < .001, respectively). Patients with 140-µm cap thickness showed greater improvement in UDVA than ones with 120-µm cap thickness at 12-month follow-up (P = .005). Both 120- and 140-μm cap thicknesses in small incision lenticule extraction were safe and effective thicknesses for correcting myopia or myopic astigmatism. The patients with 140-μm cap thickness had better improvement in UDVA after 12-month follow-up compared to patients with 120-μm cap thickness.

Vector analysis of moderate to high myopic astigmatism after small-incision lenticule extraction (SMILE): 12-month follow-up

PURPOSE

To evaluate the refractive outcomes of small-incision lenticule extraction (SMILE) surgery in moderate to high myopic astigmatism.

STUDY DESIGN

Prospective interventional case series.

METHODS

This study evaluated 111 eyes of 68 patients treated with femtosecond SMILE surgery for the correction of myopia and astigmatism. Inclusion criteria were myopia of - 0.5 D or more and astigmatism between - 1.0 D and -5.0 D. Refractive and visual measurements were obtained preoperatively, 1 and 12 month(s) postoperatively. Vector analysis was used to study the astigmatic outcomes at 12-month follow-up. Comparison of results in two groups of patients with astigmatism below and over 3.00 D was performed.

RESULTS

The preoperative mean spherical equivalent was -5.48 ± 2.17 D (range - 1.75 to - 10.00 D) and the mean cylinder was -2.02 ± 1.09 D (range - 1.00 to - 5.00 D). The mean postoperative cylinder value was -0.60 ± 0.52 D at 12-month visit. The 12-month safety and efficacy indices were 0.98 ± 0.07 and 0.97 ± 0.12, respectively. The high astigmatism group showed significantly lower safety and efficacy indices. The postoperative residual astigmatism was 0.5 D or less in 73% of the eyes. Higher amount of residual astigmatism was observed in the high astigmatism group. The angle of error was ± 5 degrees in 49% and ± 15 degrees in 87% of the eyes.

CONCLUSION

SMILE surgery is effective and safe method for correcting myopic astigmatism. Vector analysis indicated a tendency for the under correction of astigmatism in subjects with high astigmatism.

Refractive Outcomes After LASIK for the Treatment of Mixed Astigmatism with the Allegretto WaveLight EX500

INTRODUCTION

Treatment of mixed astigmatism with laser in situ keratomileusis (LASIK) is complex as the correction requires flattening the cornea in one meridian while steepening the cornea in the other meridian. The bitoric technique has become the most popular approach and has been tested across a variety of platforms. This study is the first to evaluate the results of mixed astigmatism treatment using the Allegretto WaveLight^® EX500.

METHODS

This study was a single-center, retrospective, noncomparative analysis of 400 eyes that underwent LASIK to correct for mixed astigmatism utilizing the EX500 excimer laser. Data on uncorrected distance visual acuity, corrected distance visual acuity, and spherical equivalent was analyzed at consecutive intervals (1, 3, 6, 9, and 12 months). Refractive measurements were used to perform a vector analysis.

RESULTS

Three and 12 months postoperatively, 71% and 74% of eyes had an uncorrected distance visual acuity (UDVA) of 20/20 or better and 99% and 100% of eyes had a UDVA of 20/40 or better, respectively. The postoperative UDVA was within one line of the corrected distance visual acuity (CDVA) in 88% and 93% of eyes at 3 and 12 months, respectively. At 3 months, 78% of eyes achieved refractive astigmatism no greater than 0.50 diopters and at 12 months, 80% achieved this. The mean spherical equivalent refraction was - 0.36 ± 0.57 D at 12 months after surgery. At the 12-month follow-up, the mean refractive cylinder was reduced by 87%, from - 2.79 to - 0.37 diopters. On vector analysis, 99% of eyes had an angle of error within ± 15° from the intended target at 3 and 12 months.

CONCLUSION

Treatment of mixed astigmatism using the Allegretto WaveLight^® EX500 laser exceeded the industry standards of safety, efficacy, stability, and accuracy.

Comparison of Refractive Outcomes in Small-Incision Lenticule Extraction Performed with One or Two Incisions

Purpose

To retrospectively compare the refractive outcomes between two groups of small-incision lenticule extraction (SMILE), one with a single incision and the second one with dual-incisions.

Setting

Ebsar Eye Center, Benha, Qalyopia, Egypt.

Design

A retrospective cohort study.

Methods

This study was made up of two groups (162 eyes each): all eyes in group 1 had one SMILE cut at 120°, and all eyes in group 2 had double SMILE incisions, the first incision at 120° and the second one at 270°. Refractive outcomes between the two groups were compared at 3, 6, and 12 months after surgery.

Results

The mean preoperative refractive spherical equivalent (MRSE) was −5.75 ± 2.59 D and −6.38 ± 2.18 D in group 1 and 2, respectively (P = 0.73), and a cylinder of 1.25 ± 0.83 D and 0.75 ± 0.81 D, respectively (P = 0.85). At 12 months postoperatively, in group 1, 162 eyes (100%) achieved a UCVA of 20/25, 154 eyes (95.06%) achieved a UCVA of 20/20, and 110 eyes (67.90%) achieved 20/16. In group 2, 162 eyes (100%) achieved a UCVA of 20/25, 156 eyes (96.29%) achieved a UCVA of 20/20, and 113 eyes (69.75%) achieved 20/16. The mean MRSE at 12 months postoperatively was −0.25 ± 0.33 D in group 1 and −0.5 ± 0.33 D in group 2 (P = 0.62).

Conclusion

Dual-incision SMILE is safe and effective as single-incision SMILE, with a predictable and stable effect in correcting myopia and myopic astigmatism.

SmartSurfACE transepithelial photorefractive keratectomy with mitomycin C enhancement after small incision lenticule extraction

Background

To evaluate predictability, stability, efficacy, and safety of transepithelial photorefractive keratectomy (TPRK) using smart pulse technology (SPT) (SmartSurface procedure) of Schwind Amaris with mitomycin C for correction of post small incision lenticule extraction (SMILE) myopic residual refractive errors.

Method

This study is a prospective, non-comparative case series conducted at a private eye centre in Ismailia, Egypt, on eyes with post-SMILE myopic residual refractive errors because of undercorrection or suction loss (suction loss occurred after the posterior lenticular cut and the creation of side-cuts; redocking was attempted, and the treatment was completed in the same session with the same parameters) with myopia or myopic astigmatism. The patients were followed up post-SMILE for six months before the SmartSurface procedure, and then they were followed up for one year after that. TPRK were performed using Amaris excimer laser at 500 kHz. The main outcomes included refractive predictability, stability, efficacy, safety and any reported complications.

Results

This study included 68 eyes of 40 patients out of 1920 total eyes (3.5%) with post-SMILE technique myopic residual refractive errors. The average duration between the SMILE surgery and TPRK was 6.7 ± 0.4 months (range 6 to 8 months). The mean refractive spherical equivalent (SE) was within ± 0.50 D of plano correction in 100% of the eyes at 12 months post-TPRK. Astigmatism of < 0.50 D was achieved in 100% of the eyes. The mean of the residual SE error showed statistically significant improvement from preoperative − 1.42 ± 0.52 D to 0.23 ± 0.10 D (P < 0.0001). Uncorrected distance visual acuity (UDVA) (measured by Snellen's chart and averaged in logMAR units) was improved significantly to 0.1 ± 0.07 (P < 0.0001). UDVA was 0.2 logMAR or better in 100% of the eyes, 0.1 logMAR or better in 91.2% of the eyes, and 0.0 logMAR in 20.6% of the eyes. Corrected distance visual acuity (CDVA) remained unchanged in 79.4% of eyes. 14.7% of eyes gained one line of CDVA (Snellen). 5.9% of eyes gained two lines of CDVA (Snellen).

Conclusion

Transepithelial photorefractive keratectomy using smart pulse technology with mitomycin C enhancement after SMILE is a safe, predictable, stable, and effective technique.

7-Year Results of SMILE for High Myopia: Visual and Refractive Outcomes and Aberrations

PURPOSE

To evaluate the 7-year visual, refractive, and optical outcomes following small incision lenticule extraction (SMILE) for high myopia and myopic astigmatism.

METHODS

Sixty-nine eyes (69 patients) undergoing SMILE between March 2011 and January 2012 at Aarhus University Hospital were included. Preoperative, 3-month, 3-year, and 7-year evaluation included: manifest refraction and uncorrected (UDVA) and corrected (CDVA) distance visual acuities, total corneal refractive power (TCRP), average keratometry (Km), aberrations, and central corneal thickness (CCT).

RESULTS

Preoperative spherical equivalent averaged -7.53 ± 1.18 diopters (D). Twenty-seven eyes were targeted emmetropia. In the emmetropic eyes, the postoperative logMAR UDVA remained stable (P = .11). When including all eyes, UDVA became worse from 3 to 7 years (3 months: 0.050 ± 0.16 logMAR; 3 years: 0.044 ± 0.21 logMAR; 7 years: 0.131 ± 0.29 logMAR; P < .027), whereas CDVA remained stable (3 months: -0.07 ± 0.09 logMAR; 3 years: -0.09 ± 0.08 logMAR; 7 years: -0.09 ± 0.08 logMAR, P > .99). At 7 years, 59.4% and 81.2% were within ±0.50 and ±1.00 D of target refraction, respectively. Average refractive regression was significant from 3 months to 7 years (-0.34 ± 0.69 D) and from 3 to 7 years (-0.25 ± 0.41 D, P < .05). After exclusion of three outliers with high myopic correction (< 9.63 D) and considerable regression (<-1.50 D), the average regression over 7 years was -0.25 ± 0.49 D (P = .004) with no significant change from 3 to 7 years (P = .069). Average CCT, TCRP, and anterior Km significantly increased (P < .001), whereas the posterior Km and total corneal aberrations remained stable (P > .092).

CONCLUSIONS

The long-term visual outcome remained stable after SMILE, but with an average regression of -0.34 D over 7 years. A minor group with high myopic correction exhibited considerable refractive regression years after SMILE. [J Refract Surg. 2021;37(10):654-661.].

Options and results in managing suction loss during small-incision lenticule extraction

Suction loss is an intraoperative complication in small-incision lenticule extraction (SMILE) that presents a management challenge for the refractive surgeon. The purpose of this review is to evaluate the visual, refractive, and wavefront outcomes after suction loss across the different stages of SMILE with various respective surgical treatments. Surgical management options include immediate re-SMILE by redocking or delayed re-SMILE, with or without adjustment of the laser parameters, conversion to femtosecond laser in situ keratomileusis, transepithelial photorefractive keratectomy, refractive lenticule extraction, or pseudo-SMILE. The restart treatment module on VisuMax provides appropriate retreatment recommendation. Most retreatment options for suction loss, immediate or delayed, resulted in effective, safe, and predictable outcomes, and patients were satisfied with their outcomes. Based on available level II evidence, immediate re-SMILE with or without adjustment to the laser settings achieve favorable visual and refractive outcomes in handling this intraoperative complication across all stages of SMILE.

Direct Evidence of Symmetry between Bilateral Human Corneas in Biomechanical Properties: A Comparison Study with Fresh Corneal Tissue

Purpose. To investigate the difference between the eyes from the same human with respect to the biomechanical properties of fresh corneal tissues and investigate the assumption of similarity of the corneal biomechanical properties between the eyes. Methods. Strip specimens extracted through a small incision lenticule extraction (SMILE) surgery were tested using a uniaxial tensile test. The specimens were extracted vertically. Low-strain tangent modulus (LSTM), high-strain tangent modulus (HSTM), and tensile strength (${\sigma }_b$) were the biomechanical parameters used in the comparison of the eyes from the same human. Results. Ninety corneal specimens from 45 persons were included in this study. The LSTM of the left and right eyes were 1.34 ± 0.52 and 1.37 ± 0.46 MPa, while the HSTM were 50.53 ± 7.51 and 49.41 ± 7.01 MPa, respectively. There was no significant difference between the eyes in terms of LSTM, HSTM, and${\sigma }_b\left(P=0.813,0.335,\text{and\hspace{0.17em}}0.605,\text{resp}.\right)$. The LSTM and HSTM were significantly correlated with the spherical equivalent (SE) ($P\le 0.01,P=0.001$, resp.). Conclusions. The assumption that the corneal biomechanical properties of the eyes from the same human are similar has been confirmed for the first time using fresh human corneal tissue. This finding may be useful in further biomechanical studies.

Comparison of early visual quality in patients with moderate myopia using different optical zones in small incision lenticule extraction (SMILE)

Background

The early visual qualities of patients with moderate myopia were evaluated after small incision lenticule extraction (SMILE) using different optical zones.

Methods

In this retrospective case study, 27 cases (51 eyes) were selected, including 10 cases in Group A (19 eyes), 6.6–6.8 mm in the optical zone, 10 cases in Group B (19 eyes), 6.4–6.5 mm in the optical zone, and 7 cases in Group C (13 eyes),6.1–6.3 mm in the optical zone. The following items were examined preoperatively and 1 month postoperatively: uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), spherical, cylinder, central corneal thickness (CCT), corneal mean curvature (CMC), total ocular aberrations (TA), total low order aberrations (tLOAs), defocus, astigmatism and total high order aberrations (tHOAs), spherical, coma, trefoil, modulation transfer function (MTF), MTF_cutoff, SR, objective scatter index (OSI), point scatter function at 50 and 10% (PSF50%, PSF10%), and contrast visual acuity of 100, 20, and 9% (VA100%, VA20%, and VA9%). We compared the three groups by Kruskal-Wallis test. Wilcoxon signed ranks test was used for each group before and 1 month after surgeries. P< 0.05 was considered statistically significant.

Results

There was no significant difference in UCVA, BCVA, CCT, cylinder, and CMC in three groups preoperatively and 1 month postoperatively (P> 0.05). Comparison of the aberrations of the three groups showed statistically significant difference only in TA, tLOA, defocus, astigmatism and SA preoperatively, and trefoil 1 month postoperatively(P< 0.05). The postoperative TA, tLOAs, defocus, astigmatism and trefoil of the three groups were lower than those before surgeries (P< 0.05). The postoperative tHOAs of Group B and C was lower than those before surgeries (P< 0.05). The MTF results showed that before surgeries, there were significant differences in three groups (P< 0.05) in spatial frequencies 5~15 cycles per degree (cpd), and no differences in 20~30 cpd(P> 0.05), while no difference were observed in all spatial frequencies postoperatively (P> 0.05). Comparing the preoperative and postoperative MTF values for each group, the results showed that there was a significant difference in Group C at 5~20 cpd after surgeries(P< 0.05). There was no significant difference in MTF_cutoff, SR, OSI, PSF50%, PSF10%, VA100%, VA20%, and VA9% in the three groups preoperatively (P> 0.05). One month after surgeries, higher VA9% values were measured for Group C compared to Group A and B (P < 0.05). There was no significant difference in each group before and after surgeries (P> 0.05).

Conclusion

SMILE could improve the visual qualities of patients with moderate myopia. Reducing the surgical optical zone will only affect night vision slightly.

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.

Refractive and visual outcomes of small incision lenticule extraction (SMILE) in eyes with thin corneas

OBJECTIVES

To report the refractive and visual outcomes of small incision lenticule extraction (SMILE) with the thinnest corneal thickness (CCT) of less than 500 µm and evaluate it in terms of safety and efficacy.

SETTING

Refractive Surgery Clinic of University of Health Sciences Beyoglu Eye Training and Research Hospital, Istanbul, Turkey.

DESIGN

Retrospective case series.

METHODS

The pre-and-postoperative examinations of all patients with thin corneas (preoperative CCT <500 µm) who underwent the SMILE procedure and had a minimum of 24 months of follow-up records were reviewed from medical files. The main outcome measures of the refractive and visual outcomes and the effect on corneal high order aberrations (HOAs) were evaluated.

RESULTS

The study included 55 eyes of 39 patients. The mean preoperative uncorrected visual acuity (UDVA) was 1.3 ± 1.5 logMAR, and the mean postoperative UDVA was significantly improved to 0.05 ± 0.80 logMAR at the last visit (p < 0.001). At the last follow-up, 84% of the eyes were within ± 0.50D, and 96% of the eyes were within ±1.00D of attempted SE refraction. The HOAs of coma (p < 0.001), secondary astigmatism (p = 0.015), spherical aberration (p < 0.001), and RMS (p < 0.001) aberrations increased significantly from the baseline to the postoperative last visit. The increase in trefoil was not significant (p = 0.32). No sight threatening complications or ectasia were observed during the follow-up time.

CONCLUSION

SMILE is a safe and effective technique with long-term stability for treatment of myopia in eyes with a thin cornea, and satisfactory results can be obtained if candidates for surgery are selected carefully with particular emphasis on normal preoperative corneal topography.

Outcomes of Small Incision Lenticule Extraction with Dual-Incisions in Myopic Patients

Purpose

To assess the stability, safety, predictability, and efficacy of small incision lenticule extraction (SMILE) with dual-incisions in myopic patients.

Setting

Ebsar Eye center, Benha, Qalyopia, Egypt.

Design

Single-center, retrospective, COHORT study.

Patients and Methods

The study was conducted as a retrospective non-comparative analysis of the records of 105 eyes of 53 patients treated by the SMILE with a dual-incisions technique for a mean spherical myopic error of -5.05 ± 1.93 D (range: -1.38 to -9.0 D) with or without astigmatism and the mean astigmatism of -0.90 ± 0.83 D. The mean LogMAR corrected distance visual acuity (CDVA) was -0.04 ± 0.07.

Results

One month after surgery, the mean refractive error was -0.03 ± 0.56 D (range: 0.88 to -1.50 D), and the mean postoperative astigmatism was 0.20 ± 0.31 D. The mean LogMAR UDVA was 0.07 ± 0.18 in the last follow-up visit, 12 months after surgery. At the end of the follow-up period, approximately 91.43% of patients had unchanged CDVA or gained one or more lines, 8.57% lost one line of CDVA, and 0.0% lost 2 lines.

Conclusion

SMILE with dual-incisions is effective and safe, with a stable and predictable outcome for correction of myopia and myopic astigmatism.

Advantages of Small Incision Lenticule Extraction (SMILE) for Mass Eye and Ear Special Issue

This review summarizes the advantages of Small-incision lenticule extraction (SMILE), including improved patient intraoperative experience, improved postoperative ocular surface, low incidence of regression, low re-treatment rates, and advantageous biomechanical corneal stability. Visual and refractive outcomes are similar to those achieved with LASIK, notably in large population studies. Since the inception of SMILE almost 10 years ago, the procedure has been rapidly growing in popularity. With the implementation of the novel SMILE technology in their practice, refractive surgeons generate excitement and potential for expanding the refractive market. Other parts of the world, including Asia, Europe, and Russia, SMILE has become the most popular refractive procedure performed. It is speculated that as SMILE continues to grow in popularity in the US since FDA approval in 2016 and more refractive surgeons implement this technology into their practice, it will drive an increase in the refractive market similar to what is seen in other countries.

Refractive surgery beyond 2020

Refractive surgery refers to any procedure that corrects or minimizes refractive errors. Today, refractive surgery has evolved beyond the traditional laser refractive surgery, embodied by the popular laser in situ keratomileusis or 'LASIK'. New keratorefractive techniques such as small incision lenticule extraction (SMILE) avoids corneal flap creation and uses a single laser device, while advances in surface ablation techniques have seen a resurgence in its popularity. Presbyopic treatment options have also expanded to include new ablation profiles, intracorneal implants, and phakic intraocular implants. With the improved safety and efficacy of refractive lens exchange, a wider variety of intraocular lens implants with advanced optics provide more options for refractive correction in carefully selected patients. In this review, we also discuss possible developments in refractive surgery beyond 2020, such as preoperative evaluation of refractive patients using machine learning and artificial intelligence, potential use of stromal lenticules harvested from SMILE for presbyopic treatments, and various advances in intraocular lens implants that may provide a closer to 'physiological correction' of refractive errors.

The best optical zone for small-incision lenticule extraction in high myopic patients

Small-incision lenticule extraction (SMILE) is an effective and safe procedure for the correction of myopia due to minimally invasive and noncorneal flap surgery. However, the SMILE procedure has certain requirements for corneal cap thickness, attempted refractive correction, residual stromal bed thickness, and optical zone diameter, which sometimes make surgeons hesitant to choose SMILE or other refractive surgeries. The requirements limit its use in patients with high myopia. The purpose of this review was to find the optimal parameters of SMILE through discussing the best optical zone for high myopic patients, the visual quality of different optical zones, the choice of corneal cap thickness, and their effects on corneal biomechanical parameters, so surgeons can provide reference recommendations for patients with high myopia in choosing a reasonable and safe procedure.

Six modes of corneal topography for evaluation of ablation zones after small-incision lenticule extraction and femtosecond laser-assisted in situ keratomileusis

PURPOSE

To evaluate the ablation zone diameter (AZD) using six modes of corneal topography after small-incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for myopia and to compare the programmed and postoperative AZDs METHODS: This retrospective comparative study included 86 right eyes in 86 patients who underwent SMILE or FS-LASIK at the Shandong Eye Institute between June 2016 and August 2017. Data were collected preoperatively and at 1, 3, and 6 months postoperatively using the Pentacam system. The AZD was determined using six modes of corneal topography: postoperative axial curvature topography (PACT), postoperative tangential curvature topography (PTCT), difference-axial curvature topography (DACT), difference-tangential curvature topography (DTCT), postoperative front elevation topography (PFET), and difference-corneal thickness topography (DCTT). The difference between the programmed and postoperative AZDs was compared between the groups of two surgical procedures.

RESULTS

At 3 months, the AZDs measured by PTCT, DTCT, and PFET after SMILE showed a significant decrease, while the AZD by DACT revealed an increase (P < 0.001), and the AZDs measured by PACT, PTCT, DACT, DTCT, PFET, and DCTT after FS-LASIK were all significantly decreased (P < 0.001), as compared with the programmed ablation zone values. The AZDs measured by DACT and DTCT after 3 months were larger in the SMILE group (P < 0.001); likewise, the differences between the programmed and postoperative AZDs were lower in the SMILE group (P < 0.001). Furthermore, PACT, PTCT, DACT, DTCT, and PFET indicated acceptable inter-observer reliability (ICC > 0.75).

CONCLUSIONS

In the treatment of myopia, the achieved topographic ablation zones after FS-LASIK were smaller than the theoretically designed ones. The AZDs after SMILE were larger than those after FS-LASIK, with an equivalent programmed value. The DACT may be more suitable for measuring postoperative ablation zones in clinic with clearer borders and favorable repeatability. This method may be potential for the measurement of ablation zones and further research on the visual quality after refractive surgery.

The Effect of Intraoperative Angle Kappa Adjustment on Higher-Order Aberrations Before and After Small Incision Lenticule Extraction

PURPOSE

To compare higher-order aberrations (HOAs) after small incision lenticule extraction (SMILE) in patients with and without intraoperative angle kappa adjustments.

METHODS

This is a retrospective case series. One hundred six eyes of 106 patients who underwent SMILE at Tianjin Eye Hospital (Tianjin Medical University, Tianjin, China) for correction of myopia and myopic astigmatism were divided into 2 groups. The first group consisted of eyes with intraoperative angle kappa adjustment and the second group consisted of eyes without adjustment. Preoperative and postoperative visual outcome, refraction, and HOA measurements at 1 and 3 months were compared.

RESULTS

At the pupil size of 6 mm, vertical coma at 1 and 3 months after SMILE for the angle kappa-adjusted group was 0.153 ± 0.107 and 0.157 ± 0.094 μm, which were significantly lower than those of the nonadjusted group (0.204 ± 0.117 and 0.203 ± 0.113 μm, respectively) (P = 0.026 at 1 mo, P = 0.047 at 3 mo). The change in vertical coma between preoperative and postoperative measurements was 0.011 ± 0.136 and 0.023 ± 0.129 μm at 1 and 3 months postoperatively for the angle kappa-adjusted group, which were lower than those of the nonadjusted group (0.082 ± 0.165 and 0.085 ± 0.150 μm, respectively) (P = 0.023 at 1 mo, P = 0.045 at 3 mo). Subgroup analysis for eyes with large angle kappa demonstrated that the vertical coma was significantly less in the angle kappa-adjusted group at both 1 and 3 months (P = 0.009, P = 0.043, respectively). No significant correlation was observed between angle kappa and HOAs in the angle kappa-adjusted group.

CONCLUSIONS

Adjustment of angle kappa during SMILE resulted in less HOAs. It would provide more insight on how to optimize treatment centration in SMILE.

Applying Machine Learning Techniques in Nomogram Prediction and Analysis for SMILE Treatment

PURPOSE

To analyze the outcome of machine learning technique for prediction of small incision lenticule extraction (SMILE) nomogram.

DESIGN

Prospective, comparative clinical study.

METHODS

A comparative study was conducted on the outcomes of SMILE surgery between surgeon group (nomogram set by surgeon) and machine learning group (nomogram predicted by machine learning model). The machine learning model was trained by 865 ideal cases (spherical equivalent [SE] within ±0.5 diopter [D] 3 months postoperatively) from an experienced surgeon. The visual outcomes of both groups were compared for safety, efficacy, predictability, and SE correction.

RESULTS

There was no statistically significant difference between the baseline data in both groups. The efficacy index in the machine learning group (1.48 ± 1.08) was significantly higher than in the surgeon group (1.3 ± 0.27) (t = -2.17, P < .05). Eighty-three percent of eyes in the surgeon group and 93% of eyes in the machine learning group were within ±0.50 D, while 98% of eyes in the surgeon group and 96% of eyes in the machine learning group were within ±1.00 D. The error of SE correction was -0.09 ± 0.024 and -0.23 ± 0.021 for machine learning and surgeon groups, respectively.

CONCLUSIONS

The machine learning technique performed as well as surgeon in safety, but significantly better than surgeon in efficacy. As for predictability, the machine learning technique was comparable to surgeon, although less predictable for high myopia and astigmatism.

[SMILE keratorefractive surgery technique]

Small incision lenticule extraction (SMILE) keratorefractive surgery technique is a laser surgery alternative to common methods that doesn't require laser ablation of the cornea. Despite its novelty, SMILE technique has already demonstrated positive clinical results comparable to Photorefractive Keratectomy (PRK) and Laser-Assisted in Situ Keratomileusis (LASIK), which led to its widespread application in clinical practice. Compared with other keratorefractive techniques, SMILE has a number of distinct advantage including high biomechanical stability of the cornea, low risk of dry eye syndrome, absence of a corneal flap and associated complications, preservation of corneal epithelium. The article describes the most common SMILE modifications, its weak points and possible complications, as well as methods of additional correction of remaining ametropy.

Unwanted Astigmatism and High-order Aberrations One Year after Excimer and Femtosecond Corneal Surgery

SIGNIFICANCE

Small incision lenticule extraction (SMILE) is advanced as the most minimally invasive and least traumatic corneal procedure for correcting refractive errors using a single laser. Although SMILE obtains similar results to femtosecond laser in situ keratomileusis (LASIK) with spherical myopia, it has deficiencies in astigmatism correction.

PURPOSE

The purpose of this study was to compare refractive outcomes and high-order aberrations (HOAs) between SMILE and femtosecond LASIK corneal procedures at 1 year post-operative.

METHODS

Ninety-two patients (181 eyes) with myopia/myopic astigmatism underwent either SMILE (group 1) or femtosecond LASIK (group 2). The refractive target was to achieve emmetropia in all cases. Data were analyzed to determine significance of change in refraction and HOAs. Furthermore, astigmatism was subjected to vector analysis using the Thibos (calculation of change, Δ, in J0 and J45 values) and Alpins (calculation of difference, ΔC, between target-induced astigmatism [TIA] and surgically induced astigmatism) methods.

RESULTS

Forty-five patients (89 eyes) from group 1 and 47 patients (92 eyes) from group 2 completed the study. The main significant (P ≤ .001) findings were as follows: (a) residual astigmatism was greater in group 1; (b) group 1, ΔJ0 = 1.015J0 + 0.040 (R = 0.861), ΔJ45 = 1.082J45 + 0.019 (R = 0.792), ΔC = 0.401TIA + 0.323 (R = 0.489), and mean spherical aberration increased from -0.003 (SD, ±0.059; 95% confidence interval [CI], -0.015 to 0.009) to 0.028 μm (SD, ±0.041; 95% CI, -0.037 to -0.020); and (c) group 2, ΔJ0 = 0.952J0 - 0.005 (R = 0.921), ΔJ45 = 0.962J45 - 0.002 (R = 0.923), ΔC = 0.187TIA + 0.101 (R = 0.272), mean coma reduced from 0.114 (SD, ±0.087; 95% CI, 0.096 to 0.132) to 0.077 μm (SD, ±0.059; 95% CI, 0.065 to 0.089), and trefoil from 0.089 (SD, ±0.049; 95% CI, 0.079 to 0.0990) to 0.056 μm (SD, ±0.047; 95% CI, 0.046 to 0.066).

CONCLUSIONS

In comparison with SMILE, femtosecond LASIK offered better precision in the overall control of astigmatism and HOAs.

Features of Femtosecond Correction of High Myopia through Small Access

Aim. To modify the calculated parameters of the lenticle extraction refractive surgery through a small access (SMILE), evaluate its safety and clinical efficacy in correcting high myopia.

Materials and methods. 34 patients (68 eyes) underwent surgery by a modified SMILE technology under local anesthesia. In all cases, the patients had a high degree of myopia, in 37 % in combination with astigmatism.

Uncorrected visual acuity before surgery averaged 0.05 ± 0.11, best corrected visual acuity of 0.94 ± 0.1, the pre-operative spherical refraction component was –7.23 ± 0.75, the cylindrical component was –0.48 ± 0.59.

During the operation, to obtain the maximum possible refraction result using the proposed method, the standard operation parameters were changed: the corneal flap thickness was reduced to 100 μm, the neural optical layer by 5 μm, the diameter of the optical zone depended on the residual cornea thickness, which should exceed 280–290 μm. Corneal access was increased by 15–20 degrees.

Results. The next day after surgery, monocular uncorrected visual acuity in distance in 73 % of patients was 0.8 or higher, and in 41 % of cases it was equal to or exceeded 1.0. The spherical equivalent on the first day after surgery had a slight hypermetropic shift, which was completely leveled by the year of follow-up. During the surgical intervention and in the postoperative period, no complications were noted.

Conclusion. Using the proposed algorithm for calculating the refractive effect of the operation SMILE with a high degree of myopia allows obtaining a high refractive effect and avoiding possible complications.

Clinical outcomes of small incision lenticule extraction versus advanced surface ablation in low myopia

PURPOSE

To compare the visual and refractive outcomes of small incision lenticule extraction and advanced surface ablation for low myopia or myopic astigmatism.

METHODS

Retrospective, observational case series of our first 50 consecutive small incision lenticule extraction patients compared to refraction-matched 50 advanced surface ablation treatments with attempted spherical equivalent correction ⩽-3.5 D, astigmatism ⩽-1.5 D, and corrected distance visual acuity of 1.0 (decimal scale) or better. Only one eye per patient was included.

RESULTS

Small incision lenticule extraction: mean attempted spherical equivalent correction was -2.80 ± 0.63 D. Uncorrected distance visual acuity was 0.85 and 1.0 at days 1 and 5, respectively. At 3 months, mean spherical equivalent refraction was 0.02 ± 0.32 D (range: -0.5 to +0.75 D), mean cylinder was -0.24 ± 0.21 D (range: 0 to -0.75 D), mean uncorrected distance visual acuity was 1.27, mean efficacy index was 0.96, and mean safety index was 1.05. Uncorrected distance visual acuity was same or better than corrected distance visual acuity in 96%, astigmatism ⩽0.5 D in 98% and ⩽1 D in 100% of eyes, respectively. Advanced surface ablation: mean attempted spherical equivalent correction was -2.75 ± 0.5 D. Uncorrected distance visual acuity was 0.72 and 0.61 at days 1 and 5, respectively. At 3 months, mean spherical equivalent refraction was 0.22 ± 0.32 D, mean cylinder was -0.27 ± 0.27 D, mean uncorrected distance visual acuity was 1.21, mean efficacy index was 1.03, and mean safety index was 1.08.

CONCLUSION

Small incision lenticule extraction for low myopia was found to be safe and effective with outcomes at 3 months similar to those obtained with advanced surface ablation while offering a quicker visual recovery.

[Algorithm for choosing parameters for relex smile surgery]

Presently ReLEx Smile as a method of vision correction in refractive surgery is becoming increasingly popular in Russia and abroad.

PURPOSE

to develop an algorithm for planning the surgery and choosing its parameters, and to assess the efficacy, safety and predictability of the results in the 6-month follow-up period.

MATERIAL AND METHODS

The study involved 80 patients (159 eyes) with myopia of various degrees with a mean age of 33±6 years (25 to 44 years old). Preoperative BCVA was 0.99±0.04 (0.8 to 1.0), spherical equivalent (SE) was -5.14±1.9 (-10.0 to -1.5). All surgeries were planned and performed according to the developed algorithm.

RESULTS

Results were analyzed 6 months postop. The average SE after the surgery was -0.08 D (-0.75 to +0.5). 79.5% of patients (126 eyes) were within ±0.5 D from target refraction, 6% of patients (10 eyes) received 1-2 lines of BCVA, in 87% (138 eyes) BCVA remained unchanged, 6% of patients (10 eyes) lost 1-2 lines of BCVA. 95% of patients (151 eyes) had UCVA of 0.8 and higher 6 month after the surgery, and 79% (125 eyes) achieved 1.0 vision. No significant intraoperative and postoperative complications had occurred.

CONCLUSION

ReLEx Smile is an effective, safe and predictable method of myopia correction. The newly developed algorithm reduces the risks of complications. It may be recommended for practical use by surgeons performing ReLEx Smile.

Adjustment of Spherical Equivalent Correction According to Cap Thickness for Myopic Small Incision Lenticule Extraction

PURPOSE

To evaluate the amount of spherical equivalent correction for three different cap thicknesses (120, 130, and 140 µm) during myopic small incision lenticule extraction (SMILE) and determine the association between the amount of spherical equivalent correction and several variables in each cap thickness group.

METHODS

In this retrospective, comparative, observational case series study, the authors compared refractive errors, keratometric values, laser setting (sphere correction, cylinder correction, spherical equivalent correction, optical zone, and cap diameter), and spherical aberration measured preoperatively and at 3 months postoperatively between three different cap thickness groups: 120 µm (n = 554), 130 µm (n = 377), and 140 µm (n = 90). Multiple linear regression analyses were used to determine the associations between the amount of spherical equivalent correction and several variables, including age, preoperative spherical equivalent, optical zone diameter, central corneal thickness, preoperative mean keratometric values, and preoperative corneal asphericity.

RESULTS

According to cap thickness, attempted correction is adjusted to achieve the same refractive outcomes for different cap thicknesses. There were significant differences in the amount of sphere correction and spherical equivalent correction, as well as lenticule thickness, among subgroups. Changes in keratometric values, corneal asphericity, and spherical aberration were also significantly different among subgroups (all P < .001). Changes in keratometric values, corneal asphericity, and spherical aberration significantly increased as cap thickness increased. Preoperative spherical equivalent mainly influenced the amount of spherical equivalent correction in each group.

CONCLUSIONS

Dioptric adjustment of spherical equivalent correction according to cap thickness is essential to obtain similar refractive outcomes in myopic SMILE procedures. [J Refract Surg. 2019;35(3):153-160.].

Clinical outcomes of mechanical and transepithelial photorefractive keratectomy in low myopia with a large ablation zone

PURPOSE

To evaluate the clinical outcomes, vector parameters, and aberrations between mechanical photorefractive keratectomy (PRK) and transepithelial PRK in eyes with low myopia.

SETTING

Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, Korea.

DESIGN

Retrospective, comparative case series.

METHODS

Eighty-four eyes of 84 patients with low myopia (≤2.00 diopters) were treated with mechanical or transepithelial PRK (41 eyes and 43 eyes, respectively), with the application of a large optical zone (OZ). Visual acuity, manifest refraction, slitlamp evaluation, autokeratometry, corneal topography, and the evaluation of corneal wavefront aberrations were measured preoperatively and at 1, 3, and 6 months after surgery. The efficacy, predictability, vector parameters, corneal aberrations, and safety at 6 months after surgery were compared between the two treatment groups.

RESULTS

The mean uncorrected distance visual acuity was comparable, at -0.13 ± 0.05 (SD) and -0.15 ± 0.05, in the mechanical and transepithelial PRK groups, respectively, at 6 months after surgery. The safety and efficacy indices, vector parameters, and aberrometric values were also comparable between the two groups. The OZ was large in both groups (7.09 ± 0.20 mm and 7.12 ± 0.27 mm in the mechanical PRK and transepithelial PRK groups, respectively), and showed no significant difference between groups. The corneal total root-mean-square higher-order aberrations and coma significantly reduced after treatment in both groups, and spherical aberrations significantly decreased after transepithelial PRK.

CONCLUSIONS

Mechanical and transepithelial PRK with a large OZ provided effective and safe outcomes for the correction of low myopia without differences in visual acuity and refractive outcomes between procedures.

15-Month Visual Outcomes and Corneal Power Changes of SMILE in Treating High Myopia With Maximum Myopic Meridian Exceeding 10.00 D

PURPOSE

To evaluate the long-term visual and refractive outcomes, optical quality, and stability of the cornea and axial length after small incision lenticule extraction (SMILE) for the correction of high myopia with a maximum myopic meridian exceeding 10.00 diopters (D).

METHODS

Via a prospective cohort study, 53 eyes (53 patients) with a maximum myopic meridian exceeding 10.00 D were corrected with a VisuMax femtosecond laser (version 3.0; Carl Zeiss Meditec AG, Jena, Germany) at the Zhongshan Ophthalmic Center of Sun Yat-sen University. Refractive outcomes, aberrations, axial length, and corneal curvature were evaluated preoperatively and at 1, 3, and 15 months postoperatively.

RESULTS

At 15 months postoperatively, the efficacy and safety indexes were 0.91 ± 0.25 and 1.15 ± 0.18, respectively. A total of 72% of eyes were within ±0.50 D and 89% were within ±1.00 D of the attempted spherical equivalent, respectively. From 1 to 15 months postoperatively, the significant regression was -0.24 ± 0.28 D (P < .001) on manifest refraction and -0.43 ± 0.54 D (P < .001) on anterior corneal curvature. In addition, a significant increase of 0.20 µm (P = .016) was observed in the spherical aberration. No significant change was observed in posterior corneal curvature (P > .999), including mean keratometry or astigmatism, or in the ocular axis length from 1 to 15 months postoperatively (26.82 ± 0.93 and 26.82 ± 0.95 mm, respectively, P > .99).

CONCLUSIONS

SMILE had long-term safety, efficacy, and predictability when treating high myopia with a maximum myopic meridian exceeding 10.00 D. Both a manifest refraction regression of -0.24 D and a significant spherical aberration increase of 0.20 µm were observed between 1 and 15 months postoperatively, due to the increased anterior corneal curvature. [J Refract Surg. 2019;35(1):31-39.].

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.

A Multicenter Study on Early Outcomes of Small-Incision Lenticule Extraction for Myopia

This study was aimed to investigate the early clinical outcomes of small-incision lenticule extraction (SMILE) to correct both myopia and myopic astigmatism at major clinical centers in Japan. This case series consisted of two hundred fifty-two eyes of 130 consecutive patients who underwent SMILE surgery (29.5 ± 6.3 years, mean age ± standard deviation), with spherical equivalents of -4.33 ± 1.61 D. We determined the safety, efficacy, predictability, stability, and adverse events of this procedure. Corrected distance visual acuity significantly improved, from -0.18 ± 0.04 preoperatively to -0.19 ± 0.07 logMAR postoperatively (paired t-test, p < 0.001). Uncorrected distance visual acuity also significantly improved, from 1.05 ± 0.26 preoperatively to -0.15 ± 0.11 logMAR postoperatively (p < 0.001). 88% and 98% of eyes were within ± 0.5 and 1.0 D of the targeted correction, respectively. Changes in manifest spherical equivalent from 1 week postoperatively were 0.02 ± 0.35 D (p = 0.127). No vision-threatening complications were observed in any of the cases. SMILE performed well in the correction of myopic refractive errors, and we experienced no severe complications in this series, indicating its feasibility as a surgical option for the treatment of these eyes.

Incidence and Outcomes of Sterile Multifocal Inflammatory Keratitis and Diffuse Lamellar Keratitis After SMILE

PURPOSE

To report the incidence outcomes of sterile multifocal inflammatory keratitis and diffuse lamellar keratitis (DLK) after small incision lenticule extraction (SMILE) in a large population.

METHODS

This was a retrospective review of a population of 4,000 consecutive eyes treated by SMILE at the London Vision Clinic using the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). The inclusion criterion was to have presented with inflammatory keratitis after SMILE. In some cases after SMILE, the inflammatory keratitis presented as sterile multifocal interface keratitis uncharacteristic of classic DLK. The incidence was measured and categorized as primary or secondary by presenting appearance, grade, and time to presentation. Patients were observed for 1 year after surgery and standard outcomes analysis was performed.

RESULTS

Of the 4,000 eye population, there were 18 cases (0.45%) of DLK grade 1 or 2. All cases were managed and resolved with topical steroid therapy. Of these, 12 cases (67%) were of classic appearance and 6 cases (33%) presented as sterile multifocal inflammatory keratitis. DLK was primary in nature in 11 cases (61%) and secondary in 7 cases (39%). Postoperative uncorrected distance visual acuity was 20/20 or better in 93% of eyes. No patients lost any lines of corrected distance visual acuity and there was no change in contrast sensitivity.

CONCLUSIONS

DLK occurred after SMILE with an incidence of 0.45% in this population. Topical steroid therapy resolved the DLK in all cases with no sequelae and no adverse effect on refractive or visual outcome at 1 year postoperatively. A unique type of DLK presentation can occur after SMILE, characterized by multiple focal sterile inflammatory spots. Management is the same as for classic DLK, but with a lower threshold for performing an interface washout. [J Refract Surg. 2018;34(11):751-759.].

Corneal higher-order aberrations of the anterior surface, posterior surface, and total cornea after small incision lenticule extraction (SMILE): high myopia versus mild to moderate myopia

Background

To investigate corneal higher-order aberrations (HOAs) of the anterior surface, posterior surface, and total cornea after small incision lenticule extraction (SMILE) in high myopic and mild to moderate myopic patients.

Methods

This retrospective study included 197 eyes (101 patients) undergoing SMILE surgery. According to the preoperative spherical equivalent (SE), treated eyes were divided into two groups: a high myopic group (more than − 6.0 D, Group H) and a mild to moderate myopic group (less than − 6.0 D, Group M). Corneal HOAs of the anterior surface, posterior surface, and total cornea were measured using a Scheimpflug camera preoperatively and 3 months postoperatively. Pearson’s correlation analysis was conducted to determine relationships between corneal aberrations and the SE.

Results

There were no significant differences in third-order to eight-order aberrations (RMS HOAs) of the anterior surface, posterior surface, and total corneal between the two groups before SMILE surgery. However, after SMILE, anterior and total corneal HOAs, especially vertical coma and spherical aberrations, significantly increased in both groups (p < 0.0167), whereas posterior corneal HOAs remained relatively stable (p > 0.0167). The induction of HOAs was significantly greater in Group H than Group M postoperatively (p < 0.0167). Changes in anterior surface and total corneal HOAs, especially vertical coma and spherical aberrations, were related to the SE (p < 0.05).

Conclusions

Anterior and total corneal HOAs, particularly vertical coma and spherical aberrations, significantly increased after SMILE in both groups, whereas posterior corneal HOAs remained stable. Aberration changes were related to SE.

Trial registration

Retrospectively registered. ChiCTR-ORC-17011040. Registered 1 April 2017. Name of registry: The observation of clinical results after corneal refractive surgery. Data of enrolment of the first participant to the trial: 15 December 2016.

Visual and Refractive Outcomes of Small-Incision Lenticule Extraction in High Myopia: 5-Year Results

Purpose

To report long-term visual and refractive results of small-incision lenticule extraction (SMILE) in treatment of high myopia.

Materials and Methods

Medical records of patients who underwent SMILE for surgical correction of myopia or myopic astigmatism were retrospectively reviewed. Only patients with a preoperative spherical equivalent of subjective manifest refraction (SE) ≥ 6 D and a postoperative follow-up of 5 years were included in the study. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and SE were analyzed preoperatively and at 1-, 3-, and 5-year postoperative periods.

Results

Thirty-seven eyes of 37 patients were included in the study. The mean attempted SE was −7.47 ± 1.10 D (range −6.00 to −10.00 D). At the 5-year visit, the mean difference between achieved and attempted SE was −0.43 ± 0.47 (0.50 to −1.25 D). Mean postoperative UDVA and CDVA were 0.20 ± 0.18 and 0.06 ± 0.08 logMAR, respectively. At the 1-year visit, 70% and 97% of the eyes were within ±0.50 D and ±1.00 D of the intended correction. At the 5-year follow-up, 59% and 92% percent of the eyes were within ±0.50 D and ±1.00 D of the intended SE, respectively. At the 5-year visit, the efficacy index was 0.89 ± 0.26 and the safety index was 1.16 ± 0.20. Fifty-four percent of the eyes gained one or more lines of CDVA.

Conclusion

SMILE with an intended correction of up to a spherical equivalent of 10 D is safe and effective. However, there is regression of the refractive effect over extended follow-up.