Differences in change of post-operative antioxidant levels between laser-assisted lenticule extraction and femtosecond laser in situ keratomileusis.

To evaluate the change of total antioxidant capacity (TAC) and ascorbic acid (AA) between femtosecond laser in situ keratomileusis (FS-LASIK) and laser-assisted lenticule extraction (LALEX). A prospective non-randomized study was conducted, and 33 and 75 eyes that had undergone FS-LASIK or LALEX surgeries were enrolled, respectively. The tear films near corneal incisions were collected, and the concentrations of TAC and AA were determined. The generalized linear mixed model was adopted to calculate the adjusted odds ratio (aOR) with 95% confidence interval (CI) of TAC and AA between the two groups. The AA reduction was significant 1 month after the LALEX and FS-LASIK procedures (both p < 0.05), and the decrement in AA level was significantly larger in the FS-LASIK group compared to the LALEX group (p = 0.0002). In the subgroup analysis, the LALEX group demonstrated a lower decrement in TAC level in the individuals with dry eye disease (DED) than the FS-LASIK group (p = 0.0424), and the LALEX group demonstrated a significantly lower AA decrement in the participants with high myopia (p = 0.0165) and DED (p = 0.0043). The LALEX surgery causes lesser AA decrement compared to FS-LASIK surgery especially for the patients with DED.

Refractive outcomes using Barrett formulas and patient characteristics of cataract surgery patients with and without prior LASIK/PRK.

PURPOSE: The goal of this study is to describe characteristics of cataract surgery patients who previously underwent laser in situ keratomileusis/photorefractive keratectomy (LASIK/PRK) in comparison to non-LASIK/PRK cataract surgery patients including psychiatric comorbidities, as well as describe refractive prediction error after cataract surgery while accounting for axial length (AL) using the Barrett True-K and Barrett Universal II formulas. METHODS: This was a retrospective study of patients from the University of Colorado Cataract Outcomes Registry. The primary outcomes were refraction prediction error (RPE), mean absolute RPE, and median absolute RPE. Outcomes were stratified by five axial length groups. Univariate and multivariate models for RPE were stratified by the AL group. RESULTS: Two hundred eighty-one eyes with prior LASIK/PRK and 3101 eyes without are included in the study. Patients with prior LASIK/PRK were significantly younger: 67.0 vs 69.9 years, p < 0.0001. The LASIK/PRK group had significantly better mean pre-operative BCVA in comparison to the non-LASIK group, logMAR 0.204 vs logMAR 0.288, p = 0.003. The LASIK/PRK group had significantly lower rates of cardiovascular disease (18.5% vs 29.3%, p < 0.001), hypertension (49.1% vs 59.3%, p < 0.012), and type 2 diabetes (10.7% vs 26.0%, p < 0.001), and no significant difference in psychiatric disease. The absolute RPE was higher for the LASIK group for all ALs, but only significantly higher for eyes with AL less than 25 mm. CONCLUSION: Patient eyes with prior LASIK/PRK surgery undergoing cataract surgery were significantly younger, had significantly less comorbidities, and a significantly better pre-operative BCVA. Using the Barrett formulas, absolute prediction error for eyes with longer ALs was not significantly worse for LASIK/PRK eyes than those without and the difference was smaller for eyes with longer AL.

Surgical outcomes of laser in situ keratomileusis (LASIK) in patients with stable systemic disease.

PURPOSE: To evaluate the surgical outcome in terms of safety, efficacy, predictability, and retreatment rate of LASIK surgery in patients with controlled systemic diseases in comparison with healthy individuals. METHODS: The retrospective study included data from 1936 eyes of 976 patients with stable systemic diseases who underwent LASIK surgery between January 2016 and June 2019. The safety, efficacy, predictability of the surgery, and retreatment rate were evaluated in comparison with a control group comprising 1951 patients. The study was approved by the local ethics committee and adhered to the principles of the Declaration of Helsinki. Statistical analysis was performed using R team and the level of statistical significance was set at p < 0.05. RESULTS: All treatment groups demonstrated high safety and efficacy indices after LASIK surgery. Furthermore, the study arms demonstrated comparable predictability and retreatment rates to the control group in nearly all cases. Retreatment rates were significantly higher in the rheumatoid arthritis group (p = 0.03), while safety indices were significantly lower in the hay fever group compared to the control group (p = 0.004). No intra- or postoperative sight-threatening complications were documented. CONCLUSION: Our findings suggest that selected patients with stable systemic conditions can safely undergo LASIK surgery and achieve comparable outcomes to healthy individuals. Further research is needed to better understand the treatment outcomes in this challenging patient population.

Comparison of clinical outcomes of a corneal wavefront- and topography-guided platforms for laser in situ keratomileusis on virgin eyes: an expanded cohort study.

PURPOSE: To compare the clinical outcomes of myopiacorrected with corneal-wavefront-guided (CWG) laser in situ keratomileusis (LASIK) with AMARIS 1050S (SCHWIND eye-tech-solutions GmbH & Co. KG) and corneal-topography-guided (CTG) LASIK with WaveLight EX500 (Alcon Laboratories, Fort Worth, TX). METHODS: In this prospective, pseudo-randomized expanded cohort study, a total of 266 patients were subjected to binocular LASIK surgery, either with WaveLight EX500 (WaveLight group) or Amaris 1050S (AMARIS group) platforms. Data related to right eyes were selected for analysis. Corneal higher-order aberration (HOA) was selected as the primary endpoint; while visual acuity and refraction were the secondary endpoints. All the endpoints were assessed at 3 months postoperatively. RESULTS: There were 134 eyes in the AMARIS group and 132 eyes in the WaveLight group. After 3 months of postoperative follow-up, spherical and coma aberrations were significantly lower (P < 0.05) in the WaveLight group (spherical aberration: - 0.104 ± 0.199 µm; coma aberration: - 0.117 ± 0.202 µm) in comparison with the AMARIS group (spherical aberrations: 0.254 ± 0.146 µm; coma aberrations: 0.316 ± 0.297 µm). In the AMARIS group, 96.3% of the eyes achieved an uncorrected distance visual acuity (UDVA) of 20/20 while in the WaveLight group, 96.2% of the eyes achieved an UDVA of 20/20. Furthermore, the mean postoperative manifest refraction spherical equivalent (MRSE) was - 0.02 ± 0.28 in the AMARIS group and - 0.05 ± 0.21 in the WaveLight group (P = 0.34). CONCLUSIONS: Both WaveLight EX500 and Amaris 1050S LASIK showed excellent refractive and visual outcomes. In addition, the WaveLight group showed minimal spherical and coma aberrations when compared to the AMARIS group.

Effective optical zone following small incision lenticule extraction: a review.

Small incision lenticule extraction (SMILE) is a "flapless" keratorefractive surgery with excellent safety, efficacy, stability, and predictability for myopia correction. A recent global multicenter study also reported good refractive outcomes for hyperopic SMILE. SMILE has shown advantages including improved biomechanical strength, fewer dry eye symptoms, less corneal denervation, and fewer surgery-induced higher-order aberrations over laser in situ keratomileusis (LASIK). However, night vision complaints, including glare, halos, and starbursts, could still occur after SMILE. These symptoms have been proven to be closely related to the effective optical zone (EOZ), which is defined as the achieved area of corneal ablation. A larger postoperative EOZ may indicate better visual quality, making EOZ an important safety parameter for keratorefractive surgeries. As SMILE has gained wider application globally, the EOZ following SMILE has also been increasingly studied in the field of refractive surgery. This review provides an update on topics related to the EOZ after SMILE, including its measurement and influencing factors, aiming to benefit the personalization of the surgical algorithm and ultimately improve the visual quality after the SMILE procedure.

Effect of preoperative pupil offset on corneal higher-order aberrations after femtosecond laser-assisted in situ keratomileusis.

BACKGROUND: This study aimed to investigate the relationship between multiple higher-order aberrations (HOAs) subgroups and pupil offset, as well as to analyze the factors affecting postoperative corneal HOAs in patients with different degrees of refractive errors. METHODS: We enrolled 160 patients (316 eyes) aged ≥ 18 years who had undergone femtosecond laser-assisted in situ keratomileusis (FS-LASIK) treatment. Based on the relationship between the preoperative pupil offset and the postoperative ΔHOAs, all patients were divided into two groups: group I (pupil offset ≤ 0.20 mm) and group II (pupil offset > 0.20 mm). All of the eyes had low to high myopia with or without astigmatism (manifest refraction spherical equivalent (MRSE) < -10.00 D). Uncorrected distance visual acuity, corrected distance visual acuity, MRSE, pupil offset, central corneal thickness, corneal HOAs, vertical coma (Z3-1), horizontal coma (Z31), spherical aberration (Z40), trefoil 0° (Z33), and trefoil 30° (Z3-3) over a 6 mm diameter central corneal zone diameter were evaluated preoperatively and at 1 and 3 months postoperatively. RESULTS: Our result revealed significant differences in postoperative corneal total root mean square (RMS) HOAs, RMS vertical coma, RMS horizontal coma, RMS spherical aberration, and RMS trefoil 30° between group I and group II. ΔMRSE was found to be an effective factor for ΔRMS HOAs (R2 = 0.383), ΔRMS horizontal coma (R2 = 0.205), and ΔRMS spherical aberration (R2 = 0.397). In group II, multiple linear regression analysis revealed a significant correlation between preoperative pupillary offset and Δtotal RMS HOAs (R2 = 0.461), ΔRMS horizontal coma (R2 = 0.040), and ΔRMS trefoil 30°(R2 = 0.089). The ΔRMS vertical coma effect factor is the Y-component, and the factor influencing ΔRMS spherical aberration was ΔMRSE (R2 = 0.256). CONCLUSION: A small pupil offset was associated with a lower induction of postoperative corneal HOAs. Efforts to optimize centration are critical for improving surgical outcomes in patients with FS-LASIK.

Laser in situ keratomileusis versus Artisan lens implantation in correcting ametropia after penetrating keratoplasty for keratoconus.

PURPOSE: To compare the long-term safety and efficacy of laser in situ keratomileusis (LASIK) with Artisan phakic intraocular lens implantation to correct refractive errors after penetrating keratoplasty (PK) for keratoconus. METHODS: This retrospective comparative interventional case series included a total of 33 consecutive keratoconus eyes that had previous PK and received subsequent LASIK (n = 16) or Artisan lens implantation (n = 17) were included in this study. Outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive error, and complications. RESULTS: Postoperatively, the UDVA of ≥20/40 was achieved in none of the LASIK group compared to 62.5% of eyes in the Artisan group (P < 0.001); the respective values for CDVA of ≥20/40 were 87.5 and 94.1% (P = 0.51). Spherical equivalent refraction decreased from - 6.97 ± 1.50 D preoperatively to - 4.20 ± 2.05 D postoperatively in the LASIK group (P < 0.001) and from - 10.79 ± 2.15 D preoperatively to - 2.13 ± 1.23 D postoperatively in the Artisan group (P < 0.001). There was no significant change in the refractive astigmatism in LASIK group (P = 0.30) or Artisan group (P = 0.11). The efficacy and safety indices were significantly better for Artisan (0.82 ± 0.34 and 1.13 ± 0.30, respectively) than for LASIK (0.22 ± 0.17 and 0.85 ± 0.24, respectively, P ≤ 0.006 for both comparisons). While refractive error changed significantly from postoperative year 3 to the final visit in the LASIK group, it remained stable in the Artisan group through follow-up period. No significant complications were observed in any group. CONCLUSION: Artisan lens implantation provided superior and stable visual outcomes compared to LASIK for the management of post PK refractive errors in keratoconus eyes.

Comparison of corneal flap thickness predictability and architecture between femtosecond laser and sub-Bowman keratomileusis microkeratome in laser in situ keratomileusis.

PURPOSE OF THE STUDY: The purpose of the study is to assess and compare the corneal flap thickness predictability and uniformity between Visumax femtosecond laser and Moria sub-Bowman keratomileusis microkeratome in laser in situ keratomileusis procedure to correct myopic and myopic astigmatism refractive errors. METHODS: One hundred eyes from 100 patients were enrolled in this study. Only one eye (right eye) of each patient was chosen for this study. They were divided into two groups of equal size (50 each). Target flap thickness was 90 µm. Flap thickness was measured by anterior segment optical coherence tomography in 7 specified positions at 3 months postoperative. RESULTS: For femtosecond laser group, the average central flap thickness (CFT) was 91.35 µm ± 4.97. There was no statistically significant difference between the target flap thickness and the resultant flap thickness (p = 0.12). When the central, nasal and temporal thicknesses in the same flap were compared, there was no statistically significant difference among these measurements (p = 0.9). For the microkeratome group, CFT was 102.18 µm ± 5.63. There was statistically significant difference between the target flap thickness and the resultant flap thickness (p = 0.001). The central, nasal and temporal thicknesses were compared and there was a statistically significant difference (p = 0.000). CONCLUSIONS: Our study is among few studies in the literature comparing femtosecond laser flap to SBK microkeratome flap. Femtosecond laser creates more predictable flap thickness and more uniform flap architecture. Trial registration Trial registration number: NCT04684888. Trial Registration date: December 2020. Registered at www. CLINICALTRIALS: gov .

Evaluation of morphological features: femtosecond-LASIK flap vs. SMILE cap, and the effects on corneal higher-order aberrations.

PURPOSE: The aim of this study is to evaluate morphological features of corneal flap/cap and the correlations with corneal higher-order aberrations (HOAs) changes after femtosecond laser in situ keratomileusis (FS-LASIK) and small incision lenticule extraction (SMILE). METHODS: This was a retrospective study. Pre- and postoperative (1 and 3 months) corneal HOAs were assessed with Pentacam HR. The corneal flap/cap thickness at 32 points (± 1.5 mm, ± 2 mm, ± 2.5 mm, and ± 3 mm from the corneal vertex on meridian 0°/45°/90°/135°) were measured using anterior segment optical coherence tomography at 3 months postoperatively. Morphological features of corneal flap/cap including predictability (P), uniformity (U), and symmetry (S) were calculated and used for correlation analysis with corneal HOAs changes. RESULTS: Eighty-six eyes (44 patients) and ninety-six eyes (50 patients) were involved in FS-LASIK and SMILE groups, respectively. Significant thicker corneal flap/cap than the predicted was observed at each measuring point and meridian in both groups (difference > 2.225 µm, the within-subject standard deviation over 6-mm optical zone). There was no statistically significant difference in predictability of corneal flap/cap thickness, while U6 mm (P < .0001), U0 (P < .001), U45 (P = .002), U90 (P < .0001), U135 (P = .004), S6 mm (P < .0001), S0 (P < .001), and S90 (P < .0001) over 6 mm zone were less in SMILE than in FS-LASIK. The changes of corneal tHOAs, Z (3, - 1), Z (3, 1), and SA were significantly correlated with morphological features of corneal flap/cap. CONCLUSION: Both FS-LASIK and SMILE had good predictability in flap or cap thickness, while the uniformity and symmetry of SMILE cap were better than FS-LASIK flap. The quality of flap/cap was closely associated with the changes of corneal HOAs.

Clinical outcomes of single-step transepithelial photorefractive keratectomy and off-flap epipolis-laser in situ keratomileusis in moderate to high myopia: 12-month follow-up.

BACKGROUND: To compare the quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy (TPRK) and off-flap epipolis-laser in situ keratomileusis (Epi-LASIK) in moderate to high myopia. METHODS: In this prospective self-control study, we included patients with moderate to high myopia who were randomized to undergo TPRK in one eye and Epi-LASIK in the other eye. Twelve-month follow-up results for visual acuity, refraction, ocular high-order aberrations, contrast sensitivity, postoperative pain, epithelial healing, and haze grade were assessed. RESULTS: A total of 64 eyes (32 patients) were enrolled in the study. More eyes completed re-epithelialization in the TPRK group than in the Off-flap Epi-LASIK group 3-4 days postoperatively, while all eyes completed re-epithelialization by 7 days. More eyes achieved a visual acuity (both UDVA and CDVA) of better than 20/20 in the TPRK group than in the Off-flap Epi-LASIK group. The ±0.50 D predictability for correction of the spherical equivalent (SE) was higher in the eyes of the TPRK group (91%) than in those of the off-flap Epi-LASIK group (80%) 12 months after surgery. No significant differences in ocular aberrations, including coma, spherical, and trefoil, were found between the two groups at 12 months. There were also no significant differences in visual acuity, contrast sensitivity, pain, and haze grading between the two groups. CONCLUSIONS: Both TPRK and off-flap Epi-LASIK are safe, effective, and predictable treatments for moderate to high myopia with comparable surgical outcomes. TRIAL REGISTRATION: This study was retrospectively registered on ClinicalTrial.gov ( NCT05060094 , 17/09/2021).

Diffuse lamellar keratitis as a rare complication of diamond burr superficial keratectomy for recurrent corneal erosion: a case report.

BACKGROUND: To present a case with a history of laser in situ keratomileusis (LASIK) developing diffuse lamellar keratitis (DLK) after diamond burr superficial keratectomy (DBSK) for recurrent corneal erosion (RCE). CASE PRESENTATION: A 25-year-old man presented with multiple episodes of RCE one year after femtosecond-assisted LASIK for myopia correction. Because conservative treatments failed to halt the repetitive attack of RCE, he underwent epithelial debridement and DBSK. However, severe foreign body sensation and blurred vision developed on postoperative day one. The next day, slit lamp biomicroscopy revealed DLK manifested as diffuse granular infiltrates at the flap interface. After topical corticosteroid treatment, the inflammation resolved gradually, and his vision recovered to 20/20. CONCLUSIONS: Diffuse lamellar keratitis is a rare post-LASIK complication that can be triggered by DBSK, which causes impairment of the corneal epithelial integrity and subsequent inflammation at the flap interface. For post-LASIK patients with RCE, alternative treatments, such as anterior stromal puncture, may be considered to avoid extensive disruption of corneal epithelium and DLK development depending on the size and the location of the lesions.

Vector analysis of high astigmatism (≥ 2.0 diopters) correction after small-incision lenticule extraction with stringent head positioning and femtosecond laser-assisted laser in situ keratomileusis with compensation of cyclotorsion.

BACKGROUND: The purpose of this study was to compare the astigmatic correction by vector analysis in patients with high myopic astigmatism after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) with cyclotorsion compensation or small-incision lenticule extraction (SMILE) with stringent head positioning. SETTING: Beijing Aier-Intech Eye Hospital, Beijing, China. DESIGN: A retrospective case series. METHODS: Patients who had correction of myopic astigmatism of 2 diopters (D) or more treated with either FS-LASIK with cyclotorsion compensation or SMILE with stringent head positioning were included. The results of vision and refraction were analyzed and compared between groups with the right eye. RESULTS: The study enrolled 94 patients (41eyes in an FS-LASIK with compensation of cyclotorsion group and 53 eyes in a SMILE with stringent head positioning control group. The mean preoperative manifest cylinder was -2.65 ± 0.77D in the FS-LASIK group and 2.51 ± 0.56D in the SMILE group (P = 0.302). At 12 months, there was no significant between-group difference in uncorrected distance visual acuity (UDVA, P = 0.274) and postoperative spherical equivalent (SEQ) (P = 0.107). 46.3% and 24.5% of eyes in the FS-LASIK and SMILE groups were within 0.25 D were within 0.25D postoperative cylinder, respectively, and 78% and 66% of eyes in these two groups were within 0.5 D postoperative cylinder (P = 0.027, P = 0.202). The vector analysis showed comparable between-group target-induced astigmatism (TIA) (P = 0.114), surgically induced astigmatism (SIA) (P = 0.057), difference vector (DV, P = 0.069), and the angle of error (AE) (P = 0 .213) values. The index of success (IOS) was 0.18 in the FS-LASIK group and 0.24 in the SMILE group (P = 0.024), with a significant difference between the two groups. CONCLUSION: FS-LASIK with compensation of cyclotorsion showed a favorable correction of high myopic astigmatism (≥ 2.0 D) compared to SMILE with stringent head positioning at 12 months.

Traumatic displacement of laser in situ keratomileusis flaps: an integrated clinical case presentation.

BACKGROUND: Traumatic dislocation of laser-assisted in situ keratomileusis (LASIK) corneal flaps is an uncommon postoperative complication that could occur any time after LASIK, and could be visually devastating. We evaluated the visual outcomes, corneal sensation, tear function, and dry eye questionnaire results of patients with traumatic dislocation of LASIK flaps, including one LASIK flap amputation. METHODS: This is a retrospective case series. Seven patients who were diagnosed with traumatic displacement of the LASIK flap and underwent flap replacement surgery between August 2014 and January 2019 were included.Patient's visual acuity, refraction, corneal sensitivity, non-invasive tear breakup time (NIBUT), tear meniscus height (TMH), and ocular surface disease index (OSDI) results were evaluated. RESULTS: The patients' mean age was 35.86 ± 5.84 years, and 42.9 % (3/7) were male. The mean duration from LASIK to trauma was 8.86 ± 2.48 years.The mean preoperative and postoperative six-month corrected distance visual acuity (CDVA) were 0.55 ± 0.34 and 0.02 ± 0.03, respectively. The mean spherical equivalent and astigmatism at six months postoperatively was - 1.0 ± 0.95 D and - 0.5 ± 0.25 D, respectively. The corneal flap was clear and well-positioned at the final follow-up (mean: 28.57 ± 6.9 months). 85.71 % (6/7) of the patients showed worse corneal sensation in the injured eye. Interocular OSDI discrepancy was less in those whose last visit was more than 30 months after the trauma. CONCLUSIONS: Postoperative CDVAat six months was improved, and the refractive data also showed some improvement. The corneal nerve and tear function recovery peaked before 30 months, while the OSDI continued to show a strong trend of improvement beyond 30 months.

Transient Alteration of Retinal Microvasculature after Refractive Surgery.

PURPOSE: The purpose of this study was to determine the retinal microvasculature in myopic patients after refractive surgery. METHODS: Thirty-six right eyes of 36 patients who undertook femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) were imaged using optical coherence tomography angiography preoperatively, 1-week, 1-month, and 3-month postoperation, respectively. Vessel density was analyzed after the correction of magnification, and results were correlated with clinical manifestations, including spherical equivalent (SE), amplitude of accommodation, intraocular pressure, and axial length. RESULTS: There was a significant decrease in microvascular density 1-week postoperation compared to preoperative measurement (p < 0.05), and it recovered 1-month postoperation. Microvascular densities in superficial vascular plexus (r = 0.528, p < 0.01), deep vascular plexus (r = 0.500, p < 0.01), and retinal vascular network (r = 0.390, p < 0.05) were all positively correlated with the decrease of the SE 1-week postoperation. CONCLUSION: The transient alteration of the retinal microvasculature after refractive surgery appeared to recover quickly, which may not impact the visual function after FS-LASIK.

Postoperative corneal biomechanics and influencing factors during femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and laser-assisted subepithelial keratomileusis (LASEK) for high myopia.

The purpose of this study is to compare the postoperative corneal biomechanics and assess the influence factors after femtosecond-assisted laser in situ keratomileusis (FS-LASIK) and laser-assisted subepithelial keratomileusis (LASEK) for high myopia. In this retrospective study, patients who completed 1-year follow-up were included. The corneal biomechanical parameters, including deformation amplitude ratio 2.0 mm (DA ratio 2.0 mm), integrated inverse radius (IntInv Rad), stiffness parameter at first applanation (SP-A1), and Ambrosio relational thickness through the horizontal meridian (ARTh), were measured with Corvis STII. We also investigated the relationship between these biomechanics and preoperative or intraoperative variables. Thirty eyes had FS-LASIK and 30 eyes had LASEK. The changes in DA ratio 2.0 mm, IntInv Rad, and SP-A1 after surgery were significantly smaller in the LASEK group than in the FS-LASIK group, while the change in the ARTh was not significantly different between groups. No significant differences were detected in the mean values of postoperative DA ratio 2.0 mm, IntInv Rad, and SP-A1 between LASEK and FS-LASIK, while significant difference was detected in the mean value of postoperative ARTh. There was a significant correlation between the resident stromal bed thickness and the postoperative DA ratio 2.0 mm, IntInv Rad, or SP-A1. The postoperative ARTh has shown significant correlation with postoperative central corneal thickness and the amount of myopic correction. The effect of LASEK on corneal biomechanics was smaller than FS-LASIK when the same central corneal thickness was consumed. LASEK may be performed with a lower risk of postoperative corneal ectasia than FS-LASIK.

Alteration of the pattern of regenerative corneal subbasal nerves after laser in-situ keratomileusis surgery.

PURPOSE: Corneal nerves exhibit high plasticity, which allows successful reinnervation after nerve damage caused by laser in-situ keratomileusis (LASIK) surgery. This study aimed to examine corneal subbasal nerve orientation during regeneration after LASIK. METHODS: This study involved 20 healthy, myopic subjects who had undergone bilateral Femto-LASIK 12-16 months prior with a superior hinge position. The corneal subbasal nerve plexus at the central, mid-temporal and mid-superior cornea on the right eye were imaged using in vivo confocal microscopy. Global nerve fibre orientation (indicating the overall pattern) and variation of nerve fibre orientation (indicating the consistency of the orientation) was determined using customised MATLAB™ software (www.mathworks.com/products/matlab.html). Differences in nerve orientation variables between groups were examined using the Mann-Whitney U test. Linear mixed models with Bonferroni adjustment were conducted to examine differences between corneal regions, and over time, after LASIK. RESULTS: There were no differences between post-LASIK and control groups in global nerve orientation at any of the examined corneal regions. The post-LASIK subjects had a greater variation of nerve orientation at the central (p = 0.007) and temporal (p = 0.049) cornea than the controls. There was a difference in global nerve fibre orientation between corneal regions (p < 0.001) in the controls but not in the post-LASIK group. The variation of nerve fibre orientation was higher at the central, compared to the temporal and superior cornea after LASIK (p < 0.001), although there were no differences between corneal regions in controls. CONCLUSIONS: Our results demonstrate that there was an increased variability in the corneal subbasal innervation patterns following LASIK when compared to controls.

Comparison of refractive outcomes and high-order aberrations after small incision lenticule extraction and wavefront-guided femtosecond-assisted laser in situ keratomileusis for correcting high myopia and myopic astigmatism.

PURPOSE: To compare the results of using small incision lenticule extraction (SMILE) and wavefront-guided femtosecond-assisted laser in situ keratomileusis (WFG FS-LASIK) to correct high myopia and myopic astigmatism. MATERIAL AND METHODS: The 94 eyes of 47 patients with high myopia or myopic astigmatism, if not both, who had undergone SMILE were compared with the 94 eyes of 47 patients with high myopia or myopic astigmatism, also if not both, who had undergone WFG FS-LASIK. Only eyes with high myopic or myopic astigmatism errors greater than - 6.0 diopter (D) spherical refraction and 0-3 D cylindrical refraction were included. Values of uncorrected distance visual acuity, corrected distance visual acuity, efficacy index, safety index, predictability, and high-order aberration between the patient groups were compared. RESULTS: The SMILE and WFG FS-LASIK groups did not significantly differ according to sex or age. Values of preoperative and postoperative spherical refraction, cylindrical refraction, spherical equivalent, uncorrected distance visual acuity, and corrected distance visual acuity between the groups also did not significantly differ nor did values of predictability, the efficacy index, or the safety index. SMILE induced more coma and trefoil (p < 0.001), whereas WFG FS-LASIK induced more spherical aberration (p < 0.001). CONCLUSION: Both SMILE and WFG FS-LASIK are efficient, safe, predictable procedures for correcting high myopia and myopic astigmatism. SMILE may induce more coma and trefoil, whereas WFG FS-LASIK may induce more spherical aberration.

Effect of neuroprotective citicoline eye drops on macular microcirculation.

BACKGROUND AND OBJECTIVE: To use optical coherence tomography (OCTA) examination of the retinal microvascular structures to evaluate the effect of neuroprotective eye drops (citicoline, OMK1®) administered for laser in situ keratomileusis (LASIK) surgery. PATIENTS AND METHODS: This prospective study included 45 patients treated with citicoline after LASIK and 48 patients not treated with citicoline after LASIK as a control group. In both groups, the foveal avascular zone (FAZ), retinal superficial vascular density (SVD), and deep vascular density (DVD) in the foveal and parafoveal areas were measured preoperatively and at 1 and 3 months postoperatively using OCTA. RESULTS: No significant difference was detected between the groups in terms of preoperative SVD or DVD in the foveal and parafoveal zones and all quadrants (superior, inferior, temporal, and nasal) (P > 0.05). Similarly, no significant difference was detected between the citicoline group and control group in terms of SVD or DVD in the foveal and parafoveal zones at 1 and 3 months after LASIK (P > 0.05). CONCLUSIONS: Despite their neuroprotective effect, topical citicoline drops had no significant effect on the superficial and deep microvascular structures of the retina or choriocapillaris.

Predictors affecting myopic regression in - 6.0D to - 10.0D myopia after laser-assisted subepithelial keratomileusis and laser in situ keratomileusis flap creation with femtosecond laser-assisted or mechanical microkeratome-assisted.

PURPOSE: To investigate the predictive factors of postoperative myopic regression among subjects who have undergone laser-assisted subepithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK) flap created with a mechanical microkeratome (MM), and LASIK flap created with a femtosecond laser (FS). All recruited patients had a manifest spherical equivalence (SE) from - 6.0D to - 10.0D myopia. METHODS: This retrospective, observational case series study analyzed outcomes of refraction at 1 day, 1 week, and 1, 3, 6, and 12 months postoperatively. Predictors affecting myopic regression and other covariates were estimated with the Cox proportional hazards model for the three types of surgeries. RESULTS: The study enrolled 496 eyes in the LASEK group, 1054 eyes in the FS-LASIK group, and 910 eyes in the MM-LASIK group. At 12 months, from - 6.0D to - 10.0D myopia showed that the survival rates (no myopic regression) were 52.19%, 59.12%, and 58.79% in the MM-LASIK, FS-LASIK, and LASEK groups, respectively. Risk factors for myopic regression included thicker postoperative central corneal thickness (P ≦ 0.01), older age (P ≦ 0.01), aspherical ablation (P = 0.02), and larger transitional zone (TZ) (P = 0.03). Steeper corneal curvature (Kmax) (P = 0.01), thicker preoperative central corneal thickness (P < 0.01), smaller preoperative myopia (P < 0.01), longer duration of myopia (P = 0.02), with contact lens (P < 0.01), and larger optical zone (OZ) (P = 0.02) were protective factors. Among the three groups, the MM-LASIK had the highest risk of postoperative myopic regression (P < 0.01). CONCLUSIONS: The MM-LASIK group experienced the highest myopic regression, followed by the FS-LASIK and LASEK groups. Older age, aspheric ablation used, thicker postoperative central corneal thickness, and enlarging TZ contribute to myopic regression; steeper preoperative corneal curvature (Kmax), longer duration of myopia, with contact lens, thicker preoperative central corneal thickness, lower manifest refraction SE, and enlarging OZ prevent postoperative myopic regression in myopia from - 6.0D to - 10.0D.

Comparison of visual quality after Femto-LASIK and TransPRK in patients with low and moderate myopia.

PURPOSE: To compare the visual quality after surgery of femtosecond-assisted laser in situ keratomileusis (Femto-LASIK) and transepithelial photorefractive keratectomy (TransPRK) in low and moderate myopia patients. METHODS: A prospective controlled study was performed on 114 eyes of 62 patients with low to moderate myopia, including 64 eyes of 36 cases in Femto-LASIK group and 50 eyes of 26 cases in TransPRK group. The uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), residual spherical equivalent (SE), wavefront aberration and contrast sensitivity were examined and analyses preoperatively, 1 month and 3 months postoperatively. RESULTS: The UCVA over 0.8 was 100% in two groups at 1 month and 3 months postoperatively. Femto-LASIK group (96.49%) had a higher percentage than TransPRK group (67.39%) of UCVA over 1.0 at 1 month postoperatively (p < 0.001), but it was similar in two groups (97.78%, 90.48%) at 3 months postoperatively (p = 0.15). Femto-LASIK group (77.19%, 86.67%) had a higher percentage than TransPRK group (30.43%, 52.38%) of UCVA over 1.2 at 1 month and 3 months postoperatively (p < 0.001, p = 0.001). The SE of Femto-LASIK group was 0.07 ± 0.21 D, 0.02 ± 0.23 D at 1 month and 3 months postoperatively, and of TransPRK group was 0.11 ± 0.31 D, 0.14 ± 0.38 D; two groups had no significant differences (p = 0.57, p = 0.08). The safety index was 2.0 in Femto-LASIK group and 1.6 in TransPRK, while the efficacy index was 1.67 and 0.4, respectively. The vertical coma, spherical and higher-order aberrations of Femto-LASIK group were 0.37 ± 0.54 µm, 0.31 ± 0.27 µm, 0.89 ± 0.49 µm at 1 month postoperatively, and of TransPRK group were 0.12 ± 0.38 µm, 0.14 ± 0.28 µm, 0.71 ± 0.26 µm. There was significant difference between two groups at 1 months postoperatively (p < 0.001, p = 0.001, p = 0.006), but no significant difference at 3 months (p > 0.05). The contrast sensitivity without glare in 18 c/d spatial frequencies of Femto-LASIK group was 1.08 ± 0.26 at 1 month postoperatively, and that in TransPRK group was 0.99 ± 0.22. There was significant difference between two groups (p = 0.02). The contrast sensitivity with glare in 12 c/d and 18 c/d spatial frequencies at 1 month postoperatively had significant differences between Femto-LASIK and TransPRK groups (1.52 ± 0.17, 1.10 ± 0.23 vs 1.38 ± 0.39, 1.00 ± 0.27, p = 0.02, p = 0.03). While there were no significant differences at 3 months postoperatively (p > 0.05). CONCLUSION: Femto-LASIK had a higher increase in whole eye higher-order aberrations and contrast sensitivity than TransPRK at 1 month postoperatively, but they were similar at 3 months postoperatively in low and moderate myopia patients.