Knowledge, attitudes, and practices toward femtosecond laser small incision lenticule extraction surgery and postoperative care among recipients.

BACKGROUND: To investigate the knowledge, attitudes, and practices (KAP) of individuals who underwent small incision lenticule extraction (SMILE) surgery and explore the influencing factors. METHODS: This cross-sectional study was conducted from June 21, 2023, to August 13, 2023, at Xiangyang Central Hospital. The participants were patients who had undergone SMILE surgery. The self-designed questionnaire had a Cronbach's α = 0.849. Multivariable analyses were performed to determine the factors influencing the KAP scores. RESULTS: Finally, 485 valid questionnaires were analyzed. The median knowledge score was 14 (/17, 82.4%; IQR: 12-15). The median attitude score was 15 (/20, 75.0%; IQR: 14-16). The median practice score was 48 (/60, 80.0%; IQR: 42-54). The knowledge scores correlated to the attitude (r = 0.323, P < 0.001) and practice (r = 0.202, P < 0.001) scores, while the attitude scores correlated to the practice scores (r = 0.065, P < 0.001). College diploma (OR = 0.299, 95%CI: 0.110-0.812, P = 0.018), myopia for < 2 years (OR = 0.177, 95%CI: 0.060-0.526), and not receiving proper eye training (OR = 0.588, 95%CI: 0.402-0.862) were independently associated with knowledge. Being 19-30 years old (OR = 0.421, 95%CI: 0.235-0.756), being ≥ 31 years old (OR = 0.259, 95%CI: 0.111-0.601), myopia for 2-5 years (OR = 0.476, 95%CI: 0.232-0.978), myopia for 5-10 years (OR = 0.480, 95%CI: 0.263-0.875), and moderate myopia in the right eye (OR = 1.745, 95%CI: 1.024-2.974) were independently associated with attitude. Female gender (OR = 1.826, 95%CI: 1.196-2.787), being ≥ 31 years (OR = 2.587, 95%CI: 1.113-6.014), college diploma (OR = 3.436, 95%CI: 1.366-8.641), bachelor's degree (OR = 2.826, 95%CI: 1.214-6.581), and not having proper eye training (OR = 0.458, 95%CI: 0.310-0.677) were independently associated with practice. CONCLUSIONS: Patients who underwent SMILE had high KAP regarding SMILE. This study identified KAP items that would warrant education.

Three-year results of central corneal stromal thickness reduction in small-incision lenticule extraction for high myopia correction.

BACKGROUND: To investigate the long-term corneal stromal remodeling and central stromal thickness (CST) reduction accuracy after small-incision lenticule extraction (SMILE) for high myopia correction. METHODS: This prospective study included 30 patients (50 eyes) who had undergone SMILE. Measurements of CST reduction using optical coherence tomography were performed at 1 month, 6 months, 1 year, and 3 years after surgery. Correlations were performed between planned and achieved CST reductions. RESULTS: The study enrolled 50 eyes of 30 patients. The mean spherical equivalent was -9.25±1.52 D(diopters). The postoperative CST increased in the first month after surgery and remained stable for a year. Thereafter, it remained stable during follow-up from 1 to 3 years postoperatively. The predicted CST reduction was 146.4 ± 10.3 µm. The achieved CST reductions at 1 month, 6 months, 1 year, and 3 years after surgery were 135.3 ± 12.1 µm, 130.8 ± 10.6 µm, 125.9 ± 9.4 µm, and 122.2 ± 10.6 µm, respectively. An overestimation of CST reduction was observed three years after surgery. Correlation analysis revealed a strong correlation between planned and achieved CST reductions; however, no correlation was found between CST reductions predicted error and the planned CST reductions. CONCLUSION: During long-term follow-up, our findings revealed a significant stromal remodeling following SMILE in patients with high myopia. Therefore, clinicians should consider it when screening patients with high myopia for SMILE.

Epithelial Remodeling and Epithelial Wavefront Aberrometry after Spherical vs. Cylindrical Myopic Small Incision Lenticule Extraction (SMILE).

Background/Objectives: To compare the epithelial thickness changes and the changes in epithelial wavefront aberrometry following spherical versus astigmatic myopic small incision lenticule extraction (SMILE). Methods: Eighty-six eyes of 86 patients who underwent SMILE were included in this retrospective study. A total of 43 eyes underwent myopic spherical correction (spherical group) and 43 eyes underwent myopic cylindrical correction (cylindrical group). The groups were matched according to the spherical equivalent of surgically corrected refraction. Subjective manifest refraction as well as high-resolution anterior segment optical coherence tomography (MS-39; CSO; Florence, Italy) were obtained preoperatively as well as 3 months postoperatively. The latter was utilized for computing epithelial wavefront aberrometry in addition to epithelial thickness mapping. Results: Epithelial thickness increased significantly in both groups after SMILE (p < 0.01). In the cylindrical group, epithelial thickening was more pronounced on the flat meridian compared to the steep meridian (p = 0.04). In both groups, epithelial wavefront aberrometry showed a significant postoperative increase in the epithelium's spherical refractive power, causing a myopization of -0.24 ± 0.42 diopters (D) in the spherical group (p < 0.01) and -0.41 ± 0.52 D in the cylindrical group (p < 0.0001). While no significant changes in epithelial cylindrical refractive power were observed in the spherical group, a significant increase was noted in the cylindrical group from -0.21 ± 0.24 D to -0.37 ± 0.31 D (p = 0.01). In both groups, epithelial higher-order aberrations increased significantly (p < 0.001). Conclusions: Postoperative epithelial remodeling after SMILE alters lower-order (sphere and cylinder) and higher-order aberrations of the corneal epithelial wavefront and might contribute to refractive undercorrection, especially in astigmatic corrections. Epithelial wavefront aberrometry can be used to quantify the refractive effect of epithelial remodeling processes after keratorefractive surgery.

Comparative Analysis of Visual Outcomes and Complications in Intraocular Collamer Lens, Small-Incision Lenticule Extraction, and Laser-Assisted In Situ Keratomileusis Surgeries: A Comprehensive Review.

This review provides a comparative analysis of visual outcomes and complications associated with three prominent refractive surgical techniques: intraocular collamer lens (ICL) implantation, small-incision lenticule extraction (SMILE), and laser-assisted in situ keratomileusis (LASIK). Refractive surgeries aim to correct myopia, hyperopia, and astigmatism, offering patients an alternative to corrective lenses. The review highlights the importance of comparing these procedures to guide clinical decision-making effectively. Each technique is described, emphasizing its unique advantages and considerations. While LASIK remains widely favored for its rapid visual recovery and high patient satisfaction, ICL is suitable for patients with higher refractive errors or corneal irregularities. Although relatively newer, SMILE shows promise with potential benefits such as corneal biomechanical stability and a reduced risk of dry eye syndrome. However, each procedure carries its distinct complications, reinforcing the need for personalized patient care and informed decision-making. Understanding these techniques' relative efficacy and safety profiles is essential for optimizing outcomes and enhancing patient satisfaction. Continued advancements in technology and surgical techniques promise further improvements in refractive surgery outcomes, underscoring the importance of ongoing research and innovation.

Transformation of dominant eye after small incision lenticule extraction and its effect on visual quality / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To analyze the changes of the dominant eye in myopic patients after small incision lenticule extraction(SMILE)and its effect on visual quality.METHODS: Prospective clinical study. A total of 140 patients(280 eyes)who underwent SMILE operation to correct myopia in the First Affiliated Hospital of Xinjiang Medical University from June to December 2022 were selected. They were divided into dominant eye transformation group(46 cases, 92 eyes)and non-transformation group(94 cases, 188 eyes)according to whether the dominant eye transformation occurred during the follow-up in postoperative 3 mo. The uncorrected visual acuity(UCVA)of the two groups was evaluated, the subjective visual quality was evaluated by the quality of life impact of refractive correction(QIRC)scale, and the objective visual quality was evaluated by measuring the high-order aberrations of the whole eye before and at 1 and 3 mo after surgery.RESULTS: Before SMILE, the right type of dominant eye was 105 cases, left-type was 35 cases. There were 46 cases had change at 1 mo postoperatively, and there was no new change at 3 mo after operation than 1 mo after operation. There was no significant difference in UCVA and QIRC scale score between the two groups preoperatively and at 1 and 3 mo postoperatively(P&#x003E;0.05). Comparison of the dominant eye between the two groups: the total higher-order aberrations and spherical aberrations at 3 mo postoperatively were significantly higher than those in the non-transformed group(P=0.030, 0.046); Comparison of the non-dominant eye between the two groups: trefoil in the transformed group at 1 mo postoperatively was significantly higher than that in the non-transformed group(P=0.008). The binocular difference of trefoil in the transition group was significantly higher than that in the non-transition group at 1 mo after surgery(P=0.022), with no differences in the rest parameters.CONCLUSION: Some patients may experience a change in the dominant eye after SMILE surgery, with no significant impact on subjective visual quality. The decrease of objective visual quality in the early postoperative period may be an associated factor in the dominant eye transformation.

Comparison of effective optical zone and corneal high order aberration following small incision lenticule extraction for different degrees of myopia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To compare the effective optical zone(EOZ)and corneal high order aberrations(HOAs)after small incision lenticule extraction(SMILE)among low, moderate, and high myopic patients.METHODS:A total of 134 patients who had undergone SMILE at the Second People's Hospital of Foshan from February 2019 to February 2021 were recruited, with all right eyes enrolled. The patients were divided into low myopia group(SE &#x003E;-3.00 D), moderate myopia group(-6.00 D&#x003C; SE ≤-3.00 D), and high myopia group(SE ≤-6.00 D)according to the spherical equivalent(SE). The total HOA(tHOA), spherical aberration, coma, and EOZ were measured by Pentacam preoperatively and 1 mo postoperatively, and differences in tHOA, spherical aberration, coma, and EOZ among the three groups were analyzed.RESULTS: EOZ was smaller than programmed EOZ in all groups at 1 mo after SMILE. With the increase in corrected refractive error, the EOZ decreased further(P&#x003C;0.05); The tHOA, spherical aberration, and coma were significantly higher than their corresponding preoperative values in all groups at 1 mo after surgery, and there were statistical differences in the spherical aberration of all the groups at 1 mo after surgery(P&#x003C;0.05), except for that of the mild myopia group(P&#x003E;0.05). The tHOA, spherical aberration and coma increased with corrected refractive errors; the difference in tHOA and spherical aberration was statistically significant among the three groups(all P&#x003C;0.05). Coma in the high myopia group was significantly greater than that in the moderate myopia group and the mild myopia group(P&#x003C;0.05). In addition, the coma in the moderate myopia group and the mild myopia group was not statistically significant(P&#x003E;0.05).CONCLUSION: With the increase of the refractive power corrected by surgery, the postoperative EOZ reduced more after surgery, and the HOA of the cornea is increased; corneal HOA increases at 1 mo after SMILE.

Clinical effect of cross positioning method for correcting low and moderate astigmatism during small incision lenticule extraction / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To evaluate the clinical outcomes of using the cross-positioning method for correcting low and moderate astigmatism during small incision lenticule extraction(SMILE)surgery with Alpins vector analysis.METHODS: A total of 50 patients(81 eyes)with low and moderate astigmatism with the rule ≤1.50 D who underwent SMILE surgery at the laser myopia treatment center of Xi'an No.1 Hospital from May 2022 to November 2022 were included in the prospective randomized controlled study, and they were divided into two groups according to the random table, with 25 case(41 eyes)in cross-positioning group and 25 cases(40 eyes)in control group. In the cross-positioning group, the patients' head position was adjusted based on the cross intersection lines before the standard SMILE procedure, aligning the lateral canthi with the horizontal line and the midpoint of the eyebrows and the nose bridge with the vertical line. Postoperative visual acuity and refractive results at 3 mo were observed in both groups, and astigmatic changes were analyzed and evaluated using the Alpins vector analysis method.RESULTS: During the follow-up period, 6 cases(11 eyes)in the cross-positioning group were lost to follow-up, while in the control group, 8 cases(14 eyes)were lost to follow-up, with 19 cases(30 eyes)and 17 cases(26 eyes)finally included in the cross-positioning group and the control group, respectively. At 3 mo postoperatively, the uncorrected visual acuity(UCVA)of both groups' operated eyes was ≥1.0, and no serious complications occurred, with no significant differences in UCVA, best corrected visual acuity(BCVA), spherical power, and spherical equivalent between the cross-positioning group and the control group(all P&#x0026;#x003E;0.05). The cylindrical power in the cross-positioning group was 0.00(0.00, 0.00)D, which was lower than -0.13(-0.50, 0.00)D in the control group(P=0.01). The vector analysis results showed that the difference vector(DV)in the cross-positioning group was lower than that in the control group [0.00(0.00, 0.00)vs 0.13(0.00, 0.50), P=0.01], and the index of success(IOS)was better than that of the control group [0.00(0.00, 0.00)vs 0.18(0.00, 0.77), P&#x0026;#x003C;0.01]. At 3 mo postoperatively, 26(87%)and 15(58%)eyes in the cross-positioning group and control groups achieved an angle of error(AE)within ±5°, respectively.CONCLUSION: The cross positioning method was used to calibrate the patients' head position during SMILE surgery, which reduced the axial position error and improved the accuracy of SMILE in correcting low and moderate astigmatism.

Effect of small incision lenticule extraction on the treatment of myopia patients and the impact on corneal biomechanics / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To investigate the effect of small incision lenticule extraction(SMILE)on the treatment of myopia patients, and the impact on corneal biomechanics.METHODS:Retrospective study. A total of 120 myopic patients(240 eyes)who were scheduled to undergo corneal refractive surgery in Anyang Eye Hospital from January 2020 to December 2021 were selected. The patients were divided into SMILE group(64 patients, 128 eyes)and transepithelial photorefractive keratectomy(TransPRK)group(56 patients, 112 eyes)according to the surgical treatment method. The two groups were compared in terms of uncorrected visual acuity, corneal biomechanics, corneal endothelial cell count, posterior corneal surface height and corneal surface regularity index at 1, 7 d, 1, 3, 6 mo and 1 a after surgery, and surgical complications.RESULTS:The uncorrected visual acuity of the SMILE group at 1, 7 d and 1 mo after surgery was better than that of the TransPRK group(all P&#x003C;0.001), but there was no statistically significant difference between the groups at 3, 6 mo and 1 a after surgery(all P&#x003E;0.05). Compared with preoperative values, corneal-compensated intraocular pressure, Goldmann-correlated intraocular pressure, corneal resistance factor, and corneal hysteresis in both groups showed a first decreasing and then increasing trend after surgery. The corneal-compensated intraocular pressure, Goldmann-correlated intraocular pressure, corneal resistance factor, and corneal hysteresis in the SMILE group at 1, 7 d and 1 mo after surgery were higher than those in the TransPRK group(all P&#x003C;0.05), but there was no statistically significant difference between the groups at 3, 6 mo and 1 a after surgery(all P&#x003E;0.05). There were no significant changes of corneal endothelial cell count and corneal posterior surface height in the two groups after surgery(all P&#x003E;0.05). Furthermore, corneal surface regularity index of the two groups showed a first increasing and then decreasing trend after surgery, with no statistically significant difference between the groups(P&#x003E;0.05), and there was no statistically significant difference in the incidence of postoperative complications between the groups(P&#x003E;0.05).CONCLUSION:Compared with TransPRK, SMILE has less influence on corneal biomechanics, and better visual recovery in the early stage. There is no difference in long-term visual acuity between the two surgeries, and both have good safety and effectiveness.

Comparison of different corneal residual bed thickness after small incision lenticule extraction (SMILE).

PURPOSE: To evaluate the corneal biological parameters stability between the different corneal residual bed thickness (RBT) after Small Incision Lenticule Extraction (SMILE). METHODS: In this prospective clinical trial, 127 eyes of 64 patients underwent SMILE. According to the corneal RBT, the patients were divided into the 250-270 µm, 270-290 µm and 290-310 µm groups. Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) and Scheimpflug camera (Pentacam; Oculus Optikgeräte GmbH, Wetzlar, Germany) measurements were performed preoperatively, 1 day, 1week, 1month and 3 months after surgery. RESULTS: The keratometer values among the three groups were no significant differences in postoperative periods (each P > 0.05), except the corneal thickness values (each P < 0.05). In the 250-270 µm and 270-290 µm groups, the keratometer and corneal thickness values were decreased at postoperative 1 week and increased at 1 and 3 months. The 290-310 µm group significantly higher posterior maximum elevation (PME) than the 250-270 µm group at 1 and 3 months (P = 0.022, 0.022, respectively), and higher preoperative thinnest point (PTE) at 1 week and 1 month (P = 0.013, 0.035, respectively). The PME of the 290-310 µm group was higher than the 270-290 µm group at 3 months (P = 0.045), and higher PTE at 1 week and 3 months (P = 0.022, 0.02, respectively). In all three groups, the maximal deformation amplitude (DA) was significantly higher at 1 and 3 months compared to postoperative 1 day and 1 week, and the IOP was decreased at 1 month then recovered at 3 months (each P < 0.05).The DA of the 250-270 µm group was significantly higher than the 290-310 µm group at postoperative 1 week, 1 and 3 months (P = 0.001, 0.01, 0.02, respectively). The change of the posterior corneal elevation and biomechanical parameters values were no significant differences among the three groups in postoperative periods (each P > 0.05). CONCLUSIONS: The range of 250-310 µm RBT was safe and stable at the early postoperative of SMILE. The RBT may be positively correlated with the posterior corneal elevation.

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.

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.

Intensive topical steroid regimen for enhanced very early recovery after small incision lenticule extraction.

OBJECTIVE: This study aims to investigate the topical steroid regimen after small incision lenticule extraction (SMILE) for its effect on very early restoration of visual quality. METHODS: A total of 180 patients (360 eyes) who underwent SMILE were enrolled. These patients were randomly assigned to three groups, with 60 patients in each group. The only difference among these three groups was the administration of 0.1% fluorometholone (FML) eye drops within two hours after SMILE: no FML in group A, 0.1% FML once every hour in group B and 0.1% FML once every half hour in group C. The corrected distance visual acuity (CDVA), objective scattering index (OSI), modulation transfer function (MTF) cut-off, Strehl ratio (SR) and incidence of subjective symptoms were evaluated preoperatively, at 2, 4 and 24 h and one week after SMILE. RESULTS: The CDVA, MTF cut-off and SR values were significantly higher in group C, when compared to the other two groups, at 2 and 4 h after SMILE (p < 0.05). Furthermore, the OSI and incidence of subjective symptoms were significantly lower in group C, when compared to the other two groups, at 2 and 4 h after SMILE (p < 0.05). However, no significant differences in CDVA, MTF cut-off, SR, OSI and the incidence of subjective symptoms were detected among the three groups at 24 h and one week after SMILE (p > 0.05). CONCLUSION: The administration of 0.1% FML eye drops every half hour within two hours after SMILE accelerates the restoration of visual and optical quality, and reduces the incidence of subjective symptoms during the very early phase after surgery.

Subjective patient-reported visual quality after small-incision lenticule extraction and its correlation to the objective one.

PURPOSE: The purpose of the study was to characterize the subjective visual quality and satisfaction following small-incision lenticule extraction (SMILE) and to identify its influential factors. SETTING: Peking University Third Hospital, Beijing, China. DESIGN: This was a retrospective observational study. METHODS: Patients who had simultaneous binocular SMILE for myopia and myopic astigmatism were included 6 months postoperatively, and the patient-reported outcome questionnaire was employed for the assessment of visual quality in real-life situations. Examinations with SIRIUS combined corneal topography and tomography were performed including the parameters of Strehl ratio (SR), corneal higher-order aberrations (HOAs) within 6.0-mm area, kappa angel, and thinnest corneal thickness. Decentration and effective optical zone (EOZ) were measured based on a tangential pre-post-operation difference map. Binary logistic regression analysis was performed for predictors of patient-reported visual quality. RESULTS: Clinical data from 97 cases were analyzed retrospectively. Overall satisfaction was 96.91% (94/97). Fluctuation in vision and glare is the most frequent and dominant visual symptoms. SR value increased non-significantly compared with preoperative (P> 0.05). A statistically significant (P < 0.05) increase in total HOAs, spherical aberration, and coma was noted. SR and HOAs were not correlated with the degree of visual symptoms (P > 0.05). No objective parameter was found to be associated with patient-reported visual quality after SMILE (P> 0.05). CONCLUSION: The high patient-reported satisfaction confirmed the ideal effect on visual quality following SMILE in real-life situations, though some objective optical performances were not satisfying. It is very tolerant toward patients' conditions and mild deviations, and this study did not find factors affecting visual performances.

Analysis of the correlation between biomechanical properties and corneal densitometry in myopic eyes.

Background: To investigate the correlation between corneal biomechanical characteristics (in vitro and in vivo) and corneal densitometry in myopia. Methods: The Pentacam (Oculus, Wetzlar, Germany) corneal densitometry (CD) and Corvis ST (Oculus, Wetzlar, Germany) exams were conducted prior to surgery for myopic patients who were intended to undergo small-incision lenticule extraction (SMILE). CD values (grayscale units, GSUs), and in vivo biomechanical parameters were obtained. The stromal lenticule was subjected to a uniaxial tensile test to obtain the elastic modulus E in vitro. We exam the correlations among in vivo, in vitro biomechanical characteristics and CD values. Results: In this study, 37 myopic patients (63 eyes) were included. The mean age of participants was 25.14 ± 6.74 years (range:16-39 years). The mean CD values of the total cornea, anterior layer, intermediate layer, posterior layer, 0-2 mm region and 2-6 mm region were 15.03 ± 1.23 GSU, 20.35 ± 1.98 GSU, 11.76 ± 1.01 GSU, 10.95 ± 0.83 GSU, 15.57 ± 1.12 GSU and 11.94 ± 1.77 GSU, respectively. Elastic modulus E (in vitro biomechanical indicator) was negatively correlated with intermediate layer CD (r = -0.35, p = 0.01) and 2-6 mm region CD (r = -0.39, p = 0.00). A negative correlation was also found between 0-2 mm central region CD and in vivo biomechanical indicator SP-HC (r = -0.29, p = 0.02). Conclusion: In myopic patients, densitometry is negatively correlated with biomechanical properties both in vivo and in vitro. With an increase in CD, the cornea deformed more easily.

Interface Fluid Syndrome Masquerading as Diffuse Lamellar Keratitis After Small Incision Lenticule Extraction.

A 34-year-old male with no past medical or ocular history underwent bilateral uncomplicated small incision lenticule extraction (SMILE). On day 1, uncorrected distance visual acuity (UDVA) was 20/25 in the right eye (OD) and 20/20 in the left eye (OS). The intraocular pressure (IOP) was 12 mmHg in both eyes (OU). On day 17, UDVA was 20/70 OD and 20/30+2 OS. Slit-lamp examination (SLE) revealed diffuse 2+ haze at the interface suspicious for diffuse lamellar keratitis (DLK). Topical difluprednate was added twice a day (BID). Vision decreased by day 20 with a significant myopic shift and 3+ interface haze OU. A washout of the interface was performed. Topical steroids were increased with oral prednisone. One day after the washout, vision and interface haze improved. On day 3 status post washout, UDVA decreased to 20/70 OD and 20/50 OS. IOP was 42 mmHg OU. A diagnosis of interface fluid syndrome (IFS) was confirmed. All steroids were stopped while adding ocular hypotensive medication. One month later, visual acuity was 20/20 OU with a complete resolution of interface haze. Only a handful of IFS has been documented in SMILE, an incidence that may increase as SMILE becomes more common. Among all SMILE cases, IFS was most commonly associated with steroid-induced ocular hypertension and a myopic shift around 21 days postoperatively. A fluid cleft at the interface may not always be visible with SLE, masquerading as DLK. Scheimpflug densitometry and anterior segment optical coherence tomography (AS-OCT) may aid in quantifying interface edema needed to confirm a diagnosis when IOP is unclear. A corneal washout can immediately improve corneal edema, but the preferred treatment is discontinuing all steroid medication and starting glaucoma drops.

Higher-order aberrations and visual quality after incision lenticule extraction surgery with intraoperative angle kappa adjustments between small and large kappa patients: A 2-year follow-up.

Purpose: To evaluate the postoperative visual outcomes, that is, corneal higher-order aberrations (HOAs) and visual quality, of patients with an angle kappa greater than 0.30 mm who underwent angle kappa adjustment during small-incision lenticule extraction (SMILE) 2 years after surgery compared to eyes with an angle kappa less than 0.30 mm. Methods: This was a retrospective study and included 12 patients from October 2019 to December 2019 who underwent the SMILE procedure for correction of myopia and myopic astigmatism and had one eye with a large kappa angle and another eye with a small kappa angle. Twenty-four months after surgery, an optical quality analysis system (OQAS II; Visiometrics, Terrassa, Spain) was used to measure the modulation transfer function cutoff frequency (MTFcutoff), Strehl2D ratio, and objective scatter index (OSI). HOAs were measured with a Tracey iTrace Visual Function Analyzer (Tracey version 6.1.0; Tracey Technologies, Houston, TX, USA). Assessment of subjective visual quality was achieved using the quality of vision (QOV) questionnaire. Results: At 24 months postoperatively, the mean spherical equivalent (SE) refraction was - 0.32 ± 0.40 and - 0.31 ± 0.35 in the S-kappa group (kappa <0.3 mm) and the L-kappa group (kappa ≥0.3 mm), respectively (P > 0.05). The mean OSI was 0.73 ± 0.32 and 0.81 ± 0.47, respectively (P > 0.05). There was no significant difference in MTFcutoff and Strehl2D ratio between the two groups (P > 0.05). Total HOA, coma, spherical, trefoil, and secondary astigmatism were not significantly different (P > 0.05) between the two groups. Conclusion: Adjustment of angle kappa during SMILE helps reduce the decentration, results in less HOAs, and promotes visual quality. It provides a reliable method to optimize the treatment concentration in SMILE.

The dynamic changes and influencing factors of visual symptoms after small incision lenticule extraction.

BACKGROUND: To investigate the dynamic changes and influencing factors of visual symptoms after small incision lenticule extraction (SMILE). METHODS: This was a prospective observational study. Visual symptoms including glare, haloes, starbursts, hazy vision, fluctuation, blurred vision, double vision and focusing difficulties were evaluated before and 1, 3, 6 months after SMILE using a questionnaire. Generalized linear mixed models were used to assess the effects of preoperative characteristics and objective visual quality parameters on postoperative visual symptoms. RESULTS: 73 patients/146 eyes were enrolled. Preoperatively, the most common symptoms were glare (55% of eyes), haloes (48%), starbursts (44%) and blurred vision (37%). At 1 month postoperatively, the incidence and extent scores of glare, haloes, hazy vision and fluctuation rose significantly. At 3 months, the incidence and extent scores of glare, haloes and hazy vision restored to baseline. And at 6 months, the extent scores of fluctuation returned to baseline. Other symptoms (e.g., starbursts) did not change before and 1, 3, 6 months after SMILE. Preoperative visual symptoms were associated with postoperative symptoms, as patients with a symptom preoperatively had higher postoperative scores for that symptom. Age was related to postoperative extent of double vision (coefficient = 0.12, P = 0.046). There were no significant associations between postoperative visual symptoms and preoperative SE, scotopic pupil size, angle kappa (with intraoperative adjustment), postoperative HOAs or scattering indexes. CONCLUSIONS: The incidence and extent scores of hazy vision, glare, haloes and fluctuation increased at the first month after SMILE, and recovered to baseline at 3 or 6 months. Preoperative visual symptoms were associated with the postoperative symptoms and should be fully considered before SMILE.

SMILE lenticule versus amniotic membrane graft (AMG) augmented with platelet-rich plasma (PRP) for the treatment of perforated corneal ulcer.

PURPOSE: To evaluate the safety and efficacy of stromal lenticule obtained from small-incision lenticule extraction (SMILE) surgery versus amniotic membrane graft (AMG) augmented with platelet-rich plasma (PRP) for the treatment of perforated corneal ulcers and compare the results between the two groups. PATIENTS AND METHODS: This is a comparative retrospective study that included 40 eyes with medium-sized corneal perforations, which were classified into two equal groups of 20 eyes each; group (A) was treated with SMILE lenticule graft and group (B) was treated with AMG augmented with PRP. Pre- and postoperative evaluations were carried out using both slit-lamp (SL) examination and anterior segment optical coherence tomography (AS-OCT), including closure of perforation, complete healing, and best corrected visual acuity (BCVA). RESULTS: Complete closure of the perforation was achieved in both groups. However, healing was faster in the SMILE lenticule group than in the AMG with PRP group (P < 0.05). Complete healing was achieved in both groups: 100% in SMILE lenticule group and 95% in AMG with PRP group (P > 0.05). Both groups had few insignificant complications (30% in each), which were managed. CONCLUSION: Both methods achieved adequate healing of corneal perforations within few weeks without significant complications. However, the stromal lenticule obtained from small-incision lenticule extraction (SMILE) surgery tended to be safer with faster healing than AMG with PRP.

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.

Comparison of Postoperative Safety, Efficacy, and Visual Quality after SMILE for Myopic Patients with Different Corneal Thicknesses.

PURPOSE: To investigate the safety, efficacy, and visual quality of small incision lenticule extraction (SMILE) in different corneal thickness patients with myopia or myopic astigmatism. METHODS: This prospective cohort study included 191 right eyes of 191 patients. Eyes were divided into three groups according to preoperative central corneal thickness (CCT) (Preoperative central corneal thickness (CCT) was the group indicator.) There were 31 eyes in the thin cornea group (CCT ≤500 um (µm), TC), 94 eyes in the moderate corneal thickness group (CCT ≥501 um (µm) and ≤550 um (µm), MD) and 66 eyes in the thick cornea group (CCT ≥550 um (µm), TK). Comparisons in uncorrected (UDVA) and best-corrected distance visual acuity (BDVA), manifest refractive spherical equivalent (SE), preoperative mesopic/photopic contrast sensitivity (CS), ocular higher-order aberrations (HOAs) at a 6mm analytical pupil diameter, and visual quality questionnaires were made (performed) among the three groups during the postoperative six months. Subgroup analyses were made based on preoperative SE. RESULTS: The safety indices at six months were 1.15 ± 0.18, 1.14 ± 0.17, and 1.18 ± 0.17, respectively (p = 0.374), and the efficacy indices at six months were 1.07 ± 0.25, 1.12 ± 0.22, and 1.11 ± 0.21, respectively (p = 0.599). The postoperative SE was -0.07 ± 0.52D, -0.14 ± 0.38D, and -0.05 ± 0.46D after SMILE in the three groups, respectively (p = 0.376). No significant difference was found in mesopic/photopic CS, HOAs, and visual quality among different corneal thickness groups and SE groups. Postoperative SE and efficacy indices were the lowest in thin cornea eyes with ultra-high myopia (over -9.00 D). CONCLUSIONS: SMILE provides comparable safety, efficacy, and visual quality results in different corneal thickness patients. Those with myopia higher than -9.00 D had less efficacy after surgery, especially in thin cornea patients.