Corneal pseudoectasia: a case series.

OBJECTIVE: To raise awareness of conditions that can tomographically mimic corneal ectasia and describe the actions required to avoid misdiagnosis. METHODS: We report a retrospective case series of seven patients presenting at two tertiary care centers in Israel with a presumed diagnosis of keratoconus or post-refractive ectasia. Upon further examination, the ectasia diagnosis was reconsidered and eventually ruled out. RESULTS: Included were ten eyes of seven patients. Cases included bilateral diffuse Salzmann's nodular degeneration, ophthalmoplegia with strabismus which precluded proper fixation during the acquisition of tomography images, two cases of incorrect Pentacam parameter settings, a patient with a history of hyperopic laser-assisted in situ keratomileusis (LASIK) treatment in one eye and myopic LASIK in the fellow eye, a case of old post-photorefractive keratectomy (PRK) stromal haze, and a patient with posterior polymorphous corneal dystrophy. CONCLUSIONS: Tomography patterns mimicking corneal ectasia can appear in patients without ectatic pathology. The comprehensive ophthalmologist should be aware of such cases as they may substantially alter the treatment course and prognosis of these patients.

Long-Term Evaluation of Pseudoexfoliation Syndrome Post-Cataract Extraction.

The study aimed to examine the effect of cataract extraction on ophthalmologists' ability to detect pseudoexfoliation (PXF) syndrome. A total of 31 patients admitted for elective cataract surgery were enrolled in this prospective comparative study. Prior to surgery, patients underwent slit-lamp examination and gonioscopy conducted by experienced glaucoma specialists. Subsequently, patients were re-examined by a different glaucoma specialist and comprehensive ophthalmologists. Pre-operatively, 12 patients were diagnosed with PXF on the basis of a Sampaolesi line (100%), anterior capsular deposits (83%), and pupillary ruff deposits (50%). The remaining 19 patients acted as controls. All patients were re-examined 10-46 months post-operatively. Of the 12 patients with PXF, 10 (83%) were correctly diagnosed post-operatively by glaucoma specialists and 8 (66%) by comprehensive ophthalmologists. There was no statistically significant difference in PXF diagnosis. However, detection of anterior capsular deposits (p = 0.02), Sampaolesi lines (p = 0.04), and pupillary ruff deposits (p = 0.01) were significantly lower post-operatively. Diagnosis of PXF is challenging in pseudophakic patients as the anterior capsule is removed during cataract extraction. Therefore, PXF diagnosis in pseudophakic patients relies mainly on the presence of deposits at other anatomical sites, and careful attention to these signs is required. Glaucoma specialists may be more likely than comprehensive ophthalmologists to detect PXF in pseudophakic patients.

Recurrent Keratoconus: Corneal Transplants for Keratoconus Develop Tomographic Ectatic Changes.

PURPOSE: The purpose of this study was to evaluate postoperative Scheimpflug imaging changes during the first 5 years after penetrating keratoplasty (PK) in patients with keratoconus (KC). METHODS: This retrospective, interventional case series includes 31 eyes of 31 patients who underwent their first PK with a history of KC. Postoperative Scheimpflug imaging was performed 3 months after the removal of the last suture (baseline) and then repeated 3 and 5 years after the PK. Demographic data, donor and host trephination diameter, and Scheimpflug imaging (Pentacam HR, Oculus, Germany) parameters indicative of ectasia were analyzed to evaluate postoperative graft changes that occur after PK. RESULTS: The maximal keratometry (Kmax) progressed significantly between baseline (53.5 ± 6.1 D) and postoperative year 3 and year 5 [56.5 ± 6.1 diopter (D) and 58.8 ± 7.9 D, P < 0.001]. Significant changes were also observed for the anterior best fit sphere and posterior best fit sphere ( P < 0.001 for 3 and 5 years compared with baseline). Kmax increased by at least 2 Ds for 74.2% of patients and up to 7 Ds or more for 25.8% of the patients. A significant inverse correlation was observed for host trephine size and progression of Kmax (r = -0.52, P = 0.01), which indicated that larger host trephination size was associated with a smaller increase in postoperative Kmax. CONCLUSIONS: Tomographic graft changes indicative of ectasia were observed within 3 to 5 years after PK in patients with KC. These changes were observed more frequently and sooner after corneal transplants than previously reported.

Post-refractive surgery of Israeli Defense Forces recruits in 2005-2018-prevalence, combat unit drop-out rates and utilization of eye-care services.

PURPOSE: To assess the number of recruits for military service in the Israeli Defense Force (IDF) who underwent refractive surgery prior to enlistment and examine whether the procedure affected their ability to accomplish combat training. SETTING: Medical records of IDF recruits. DESIGN: Retrospective analysis of medical records of recruits with ametropia who underwent or did not undergo refractive surgery prior to enlistment. METHODS: Recruits were categorized into ametropes and recruits who underwent refractive surgery. Fitness and assignment to combat units and completion status of combat training were compared between the two groups. RESULTS: The study included 334,688 (182,969 males, 151,719 females) ametropes of which 5231 (4753 males, 478 females) underwent refractive surgery prior to recruitment. Refractive surgery prevalence increased from 9/1000 ametropes in 2005 to 18.5/1000 ametropes in 2018 (r = 0.912, p < 0.001); 2643 of the operated recruits (50.5%) had their surgery at the age of 17-18. Dropout rates from combat training were significantly lower in the refractive surgery group during the study period (1.68% vs. 6.14%, respectively, p < 0.001). Soldiers in the operated group were more frequently referred to ophthalmologists than those in the ametropes group and less frequently referred to optometrists. CONCLUSIONS: The prevalence of refractive surgery in IDF recruits has increased substantially during the last decade with more of them applying to combat units. Refractive surgery opened new possibilities for recruits who were unfit for combat duty prior to surgery and did not appear to impair the chances of successfully completing combat training.

ABCD progression display for keratoconus progression: a sensitivity-specificity study.

OBJECTIVE: To evaluate the sensitivity and specificity of the ABCD progression display for keratoconus progression. METHODS: Data was collected from patients that underwent at least two Pentacam assessments 6 months apart. Sensitivity and specificity were calculated for the ABCD progression display. Progression was defined by criterion 1: change in two ABCD parameters above 80% confidence interval (CI) or criterion 2: change in one ABCD parameter above 95%CI. Receiver operating characteristic analysis compared the area under the curve (AUC) of all ABCD parameter combinations. RESULTS: Thirty eyes were evaluated over a median time of 10.3 months. Progression by criterion 1 resulted in a sensitivity of 61.9% and specificity of 88.9%. Progression by criterion 2 resulted in higher sensitivity (80.9%) and specificity (100%). Pairwise comparisons of the ROC curves show that the AUC achieved by criterion 2 was significantly higher than criterion 1 (0.905 vs. 0.754, p = 0.0332). Evaluation of all ABCD combinations with a significant change of 80% or 95% CI did not show superiority over criterion 1 or 2 regarding progression detection. The D parameter had a very low AUC (0.5-0.556). CONCLUSIONS: The ABCD progression display can assess keratoconus progression with high sensitivity and specificity, thus assisting the patients' decision-making process. The D parameter did not contribute to the sensitivity or specificity of this classification.

[MICROSPORIDIUM KERATITIS: A CASE SERIES].

INTRODUCTION: Microsporidia is a phylum of intracellular parasites that secrete spores and stay in water sources. These parasites can cause infection in humans by invading the digestive system, the urinary system, the muscular system and the eye. Recently, the Israeli Ministry of Health announced that dozens of people in Israel were suspected of being infected with microsporidial keratitis after bathing in the waters of the Kinneret (Sea of Galilee). Here we present a brief overview of this microsporidial keratitis as well as three case presentations.

Validation of the multi-metric D-index change in the assessment of keratoconus progression.

PURPOSE: To validate the effectiveness of the multi-metric D-index by Pentacam in detecting keratoconus (KC) progression. MATERIALS AND METHODS: This was a retrospective study of KC patients at the Rabin Medical Center, Petah Tikva, Israel, during 2016-2018 with at least two corneal tomography examinations six months apart. Agreement between clinical diagnosis of progression (1.5D increase in mean keratometric value, 1D increase in Kmax, a 5% decrease in central corneal thickness (CCT), worsening of visual acuity by more than one line, or deterioration of manifest corneal astigmatism > 1.5D) and the D-index was evaluated. Receiver operating characteristic (ROC) analysis was used to find the D-index's optimal cutoff value to show progression. RESULTS: We included KC eyes in the stable group (N = 7) and the progression group (N = 54). Patient demographics and tomographic parameters at baseline were similar between the groups. The D-index change was significantly higher in the progression group than in the stable group (median + 1 and 0.0, respectively, p = 0.024). Based on the ROC analysis, the optimal D-index cutoff change within at least six months was 0.32 (59.3% sensitivity and 100% specificity (area under the curve [AUC] = 0.771, Youden = 0.592). Subjects with a D-index change above this value had a 21.1-fold increase in odds for corneal ectasia progression requiring CXL (OR: 21.1, 95%CI 1.17-398.8, p = 0.038). CONCLUSION: The multi-metric D-index can serve as a clinically feasible parameter to detect KC progression and guide patients' referral for further interventions.

Stromal peeling for deep anterior lamellar keratoplasty in post-penetrating keratoplasty eyes.

BACKGROUND/AIMS: To evaluate the clinical outcomes of deep anterior lamellar keratoplasty performed by stromal peeling in eyes that have previously undergone penetrating keratoplasty (PK) for keratoconus. METHODS: Standardised stromal exchange included (1) 9 mm trephination of the recipient bed outside the old PK wound, (2) creation of a partial anterior corneal flap through lamellar dissection across the PK wound, (3) opening the stromal component of the old PK wound using blunt-tipped Vannas scissors until a plane of separation is reached, (4) severing the attachment of the PK surgical scar from the recipient host, (5) peeling the stroma of the PK graft from the underlying tissue and (6) suturing the donor anterior corneal lamella prepared by microkeratome dissection (450 µm depth, 9 mm diameter). Main outcome measures were success rate, best spectacle-corrected visual acuity (BSCVA) and endothelial cell loss (ECL). RESULTS: Of 21 post-PK eyes, stromal exchange succeeded in all but three cases, which were converted to a two-piece mushroom PK. After complete suture removal, mean BSCVA significantly improved from 0.95±0.39 logMAR preoperatively to 0.23±0.17 logMAR (p<0.001). Mean ECL was 5.4±23.2%. Double anterior chamber formation occurred in eight cases (44%), which all resolved after a single re-bubbling. CONCLUSION: In post-PK eyes, stromal exchange can be performed by means of simple peeling without deep anterior lamellar dissection of the previous PK graft. Large-diameter (9 mm) repeat keratoplasty through stromal peeling yields excellent visual outcomes and minimal ECL. Double anterior chamber formation may complicate the postoperative course, but prompt intervention allows successful management.

Transepithelial photorefractive keratectomy on the same day of the initial consultation for the correction of myopia.

PURPOSE: To examine the clinical outcomes, efficacy, safety, and predictability of transepithelial photorefractive keratectomy (Trans-PRK) operations performed on the day of the first screening visit in comparison with operations scheduled at a following appointment. METHODS: Data of consecutive patients with myopia of various degrees, who underwent Trans-PRK, were retrospectively analyzed. Findings were compared between patients who underwent Trans-PRK on the same day of first consultation to patients that underwent surgery at subsequent visits, following initial consultation on a different day. RESULTS: The study included 599 eyes treated on the initial visit day and 1936 eyes treated on a subsequent visit. Mean final spherical equivalent was close to emmetropia in both groups (p = 0.183). Efficacy indices were 0.928 ± 0.192 in the initial-visit group and 0.945 ± 0.163 in the second-visit group (p = 0.152). Safety indices were 0.954 ± 0.156 and 0.955 ± 0.151 (p = 0.707), respectively. No differences between the groups were seen in uncorrected visual acuity (UDVA) of ⩾20/20, ⩾20/25, and ⩾20/32. Only the sub-analysis of patients reaching UDVA of 20/40 or better was slightly lower in the first-visit (95.5%) compared with the second-visit group (97.9%, p = 0.001). Results of attempted correction within ±0.50 D were: 63.3% and 69.0%, respectively (p = 0.009). Complications profiles in the two groups were comparable. CONCLUSIONS: Trans-PRK completed on the day of the first screening appointment demonstrated a similar safety outcome compared with subsequent-visits procedures, and slightly lower, yet comparable, results regarding efficacy and predictability.

Outcomes of Repair of Total Graft Detachment following Descemet's Membrane Endothelial Keratoplasty. / Rettungsversuche einer vollständigen Transplantatablösung nach Descemet-Membran-Endothelkeratoplastik.

OBJECTIVE: To present the outcomes of attempts to salvage total graft detachment following Descemet's membrane endothelial keratoplasty (DMEK). METHODS: A search of the electronic medical records of two tertiary medical centers for all patients who underwent DMEK yielded six cases of postoperative total graft detachment (2.54%). Graft salvage was attempted in all cases using repeated intracameral graft staining, unfolding, and reattachment to the stroma under 20% hexafluoride gas. RESULTS: In all cases, a free-floating totally detached graft was identified in the anterior chamber shortly after surgery. Salvage surgery resulted in a central, well-oriented, and fully attached graft. In three cases, the primary graft failed, and in two, the corneas cleared at first but failed after 2 months and 1 year respectively. In one case, the cornea remained clear during 1 year of follow-up but had a very low endothelial cell density. CONCLUSION: Reattachment of fully detached DMEK graft is technically possible, but graft manipulation during the primary and secondary operations is likely to damage the endothelial cells, resulting in primary or early graft failure. If graft salvage is attempted, the probability of primary or early graft failure should be discussed with the patient, and expectations should be tempered accordingly.

Ultrastructural Alterations of Grafted Corneal Buttons: The Anatomic Basis for Stromal Peeling Along a Natural Plane of Separation.

PURPOSE: To examine the ultrastructure of the natural plane of separation in grafted corneas and evaluate the outcomes of stromal peeling. DESIGN: Interventional case series. METHODS: In this multicenter study, stromal peeling was attempted in 96 consecutive eyes with unsatisfactory vision following penetrating keratoplasty (PK) for keratoconus (n = 79), herpetic keratitis (n = 11), and granular dystrophy (n = 6). Stromal exchange was performed by (1) 9 mm partial-thickness trephination; (2) creation of a corneal flap across the PK wound; (3) opening of the stromal component of the PK wound until a smooth, translucent natural plane was identified; (4) severing the attachment of the PK scar; (5) stromal peeling along the identified plane; and (6) suturing of donor lamella. Grafted corneas from cases that mandated conversion to PK were processed for transmission electron microscopy. RESULTS: The natural plane of separation was identified in all cases. Stromal exchange was successfully completed in 84 cases (87.5%). Snellen visual acuity ≥20/40 and ≥20/25 was reached in 93% and 72% of cases at 3 years (n = 49) and 86% and 62% at 4 years (n = 21) postoperatively. Mean endothelial cell loss at 1 year was 6.6% ± 9.5%. Stromal peeling occurred along a plane lined with a continuous layer of keratocytes separating pre-Descemet membrane (DM) stroma, DM, and endothelium from the anterior stroma. Pre-DM stroma was made of poorly organized lamellae containing widely spaced, randomly arranged collagen fibrils. CONCLUSIONS: Ultrastructural alterations in the stromal microarchitecture of grafted corneas provide evidence of a natural plane of separation identified intraoperatively. Stromal peeling can be successfully performed in post-PK eyes with various stromal pathology.

Descemet Membrane Endothelial Keratoplasty in Eyes With Chronic Ocular Hypotony Following Glaucoma Surgery.

PURPOSE: To assess the outcomes of Descemet membrane endothelial keratoplasty (DMEK) in patients with ocular hypotony after glaucoma surgery. DESIGN: retrospective case series. METHODS: Setting: Multicenter retrospective case series. PATIENTS/INTERVENTION: Hypotonic eyes with prior glaucoma surgery that underwent DMEK between January 2013 and July 2019 in Israel (2 centers) and Canada (1 center). MAIN OUTCOME MEASURES: Pre/postoperative corrected distance visual acuity, complications, 3- to 6-month endothelial cell loss, and intraocular pressure (IOP). RESULTS: The study included 11 DMEK procedures performed in 10 eyes of 4 males and 6 females aged 65-84 years. Indications for DMEK included 7 cases of pseudophakic bullous keratopathy, 2 cases of failed DMEK, and 1 case of failed Descemet stripping automated endothelial keratoplasty. All patients had at least 1 previous trabeculectomy operation. One patient had 2 trabeculectomy procedures and 1 tube placement procedure. Two patients had 1 previous trabeculectomy and 1 tube placement procedure. The corrected distance visual acuity improved significantly from 1.52 ± 0.68 logarithm of minimal angle of resolution preoperatively to 0.49 ± 0.32 logarithm of minimal angle of resolution 3 months postoperatively (P < .001). Rebubbling occurred in 3 of 11 procedures (27%). Endothelial cell loss 6-12 months postoperatively was 60% ± 16% (range, 41%-89%). At the last follow-up visit, 6 of 11 (54%) of the grafts were clear. The remaining 5 grafts failed at 1-4 years postoperatively. The preoperative IOP was 5.1 ± 1.6 mm Hg (range, 1-7 mm Hg). In all but one patient, the postoperative IOP did not increase to more than 13 mm Hg. In 2 cases, the IOP decreased from 5 and 7 mm Hg preoperatively to 1 mm Hg 1 year postoperatively. CONCLUSION: DMEK is a valid procedure for the treatment of corneal edema in hypotonic eyes after glaucoma procedures. These eyes benefit from improvement in vision after DMEK.

Descemet Membrane Endothelial Keratoplasty Outcomes between Young and Old Graft Recipients.

Purpose: To evaluated Descemet's membrane endothelial keratoplasty (DMEK) outcomes in young and old graft recipients.Materials and Methods: Data of 164 surgeries with a median age of 76 years (interquartile range 14 years) undergoing DMEK surgery between 2016 and 2018 was reviewed. Complications, graft survival, and visual acuity gain were compared between subjects in the 25th percentile (young recipients; aged 70 years and less, n = 21) and 75th percentile (old recipients; aged 85 years and over, n = 27) over the 2-year follow-up.Results: Young recipients had a lower rate of pre-operative glaucoma (14.3% vs. 51.9%, p = .014) and pseudophakic bullous keratopathy (9.5% vs. 59.3%, p < .001), and a higher rate of Fuchs endothelial dystrophy (57.1% vs. 14.8%, p = .002) and combined cataract extraction at the time of DMEK surgery (52.4% vs. 7.4%, p = .001) when compared to old recipients. Complications (primary graft failure, pupillary block, cystoid macular edema or infectious keratitis) were independent of graft recipient age. Descemet's membrane detachment requiring re-bubbling was observed more often in young compared to the old recipients (42.9% vs. 14.8%, p = .049). Visual acuity gain between the groups remained comparable up to 1-year, whereas at 2-years old recipients showed significantly declined visual acuity gains compared to the young recipients (0.14 ± 0.68 vs. 0.74 ± 0.49, p = .012). Graft recipients aged over 85 years had a considerably higher graft failure rate over the 24-months (40.7% vs. 4.8%, p = .006) and shorter graft survival time (p = .002; log-rank) when compared to the recipients aged under 70 years. After adjusting for potential confounders such as Fuchs endothelial dystrophy, pseudophakic bullous keratopathy and glaucoma, the recipients aged over 85 remained at higher risk for graft failure (HR = 17.278, 95% CI = 1.787-167.1, p = .014).Conclusions: In aged DMEK recipients, regardless of the low incidence of early postoperative complications, the rate of postoperative graft failure was significantly higher and graft survival shorter than in younger recipients.

High Agreement between Barrett Universal II Calculations with and without Utilization of Optional Biometry Parameters.

PURPOSE: To examine the contribution of anterior chamber depth (ACD), lens thickness (LT), and white-to-white (WTW) measurements to intraocular lens (IOL) power calculations using the Barrett Universal II (BUII) formula. METHODS: Measurements taken with the IOLMaster 700 (Carl Zeiss, Meditec AG, Jena, Germany) swept-source biometry of 501 right eyes of 501 consecutive patients undergoing cataract extraction surgery between January 2019 and March 2020 were reviewed. IOL power was calculated using the BUII formula, first through the inclusion of all measured variables and then by using partial biometry data. For each calculation method, the IOL power targeting emmetropia was recorded and compared for the whole cohort and stratified by axial length (AL) of the measured eye. RESULTS: The mean IOL power calculated for the entire cohort using all available parameters was 19.50 ± 5.11 diopters (D). When comparing it to the results obtained by partial biometry data, the mean absolute difference ranged from 0.05 to 0.14 D; p < 0.001. The optional variables (ACD, LT, WTW) had the least effect in long eyes (AL ≥ 26 mm; mean absolute difference ranging from 0.02 to 0.07 D; p < 0.001), while the greatest effect in short eyes (AL ≤ 22 mm; mean absolute difference from 0.10 to 0.21 D; p < 0.001). The percentage of eyes with a mean absolute IOL dioptric power difference more than 0.25 D was the highest (32.0%) among the short AL group when using AL and keratometry values only. CONCLUSIONS: Using partial biometry data, the BUII formula in small eyes (AL ≤ 22 mm) resulted in a clinically significant difference in the calculated IOL power compared to the full biometry data. In contrast, the contribution of the optional parameters to the calculated IOL power was of little clinical importance in eyes with AL longer than 22 mm.

Subconjunctival Aflibercept for the Treatment of Formed Corneal Neovascularization.

PURPOSE: To evaluate the effect of a single subconjunctival aflibercept injection on formed corneal neovascularization. METHODS: A prospective clinical trial, conducted at a single tertiary medical center. Included were consecutive patients with corneal pathologies complicated by corneal neovascularization, who were candidates for anti-vascular endothelial growth factor treatment at the discretion of a cornea specialist. A single subconjunctival injection of 0.08 mL of Aflibercept (Eylea 25 mg/mL) was administered near the limbus in proximity to the areas of maximal pathological neovascularization. Follow-up visits were scheduled on days 7, 30, 60, and 90 following injection. Best-corrected visual acuity (BCVA), intraocular pressure, slitlamp examination, digital cornea photography, specular microscopy, and anterior-segment optical coherence tomography were documented at each visit. The images were graded by a masked observer for density, extent, and centricity of corneal vascularization. RESULTS: Six eyes of six patients were analyzed. No clinically significant ocular or systemic adverse events were documented. No change was noted in extent, density, or centricity of corneal blood vessels at seven, 30, and 90 days after injection (P>0.1 for all time point comparisons, Friedman test). Best-corrected visual acuity fluctuated insignificantly in 5/6 patients during follow-up time, and objective but not subjective improvement of BCVA was noted in one patient with no concurrent change of neovascularization. The recruitment has therefore halted prematurely. CONCLUSIONS: A single subconjunctival aflibercept injection seems to be well tolerated. However, it is ineffective for regressing formed corneal neovascularization.

Refractive outcomes of high-magnitude astigmatism correction using femtosecond LASIK versus transepithelial PRK.

PURPOSE: To compare the outcomes of femtosecond laser assisted in situ keratomileusis (FS-LASIK) with transepithelial photorefractive keratectomy (T-PRK) for the correction of high-grade astigmatism. METHODS: Medical records of patients with astigmatism of 2 diopters (D) or higher, who were treated with FS-LASIK or T-PRK in 2013 through 2014 at a private practice laser clinic, were retrospectively analyzed. Efficacy, safety, predictability and vector analysis of astigmatism correction were compared between the treatment groups. RESULTS: The study included 93 eyes treated with FS-LASIK and 186 eyes treated with T-PRK. No significant differences in postoperative spherical equivalent (-0.10 ± 0.7 D and -0.11 ± 0.7 D, respectively, p = 0.958) and postoperative refractive astigmatism (0.79 ± 0.54 D and 0.82 ± 0.63 D, respectively, p = 0.685) were demonstrated. A significant advantage of FS-LASIK over T-PRK was seen for the efficacy (1.00 ± 0.18 and 0.86 ± 0.22, respectively, p < 0.001) and safety (1.03 ± 0.17 and 0.89 ± 0.21, respectively, p < 0.001) indices. Results remain statistically significant in a multivariate analysis model. Vector analysis for the astigmatism correction showed no significant difference between the surgery methods in the surgically induced astigmatism, difference vector, correction index and index of success. CONCLUSION: Both procedures demonstrated desirable post-operative SE outcomes for high-grade astigmatism correction. However, FS-LASIK achieved better results than T-PRK in the efficacy and safety parameters.

Femtosecond laser assisted in situ keratomileusis (FS-LASIK) yields better results than transepithelial photorefractive keratectomy (Trans-PRK) for correction of low to moderate grade myopia.

INTRODUCTION: The purpose of this study was to compare the outcomes of transepithelial photorefractive keratectomy (Trans-PRK) with femtosecond laser assisted in situ keratomileusis (FS-LASIK) for the correction of low to moderate myopia. METHODS: A retrospective cohort study design was used. The study group included patients with myopia less than -6.0 D, with or without concomitant astigmatism under 2.0 D, who were treated with FS-LASIK or Trans-PRK in 2013 through 2014. Background, clinical and outcome data were collected from the patient files. A comparison between eyes treated with FS-LASIK or Trans-PRK was performed. RESULTS: The Trans-PRK group was comprised of 1793 eyes and the FS-LASIK group of 666 eyes. Mean ± SD spherical equivalent (SE) refraction prior to surgery was -3.43 ± 1.27 D in the Trans-PRK group and -3.18 ± 1.34 D in the FS-LASIK group (p < 0.001). Efficacy index values were 0.95 ± 0.14 in the Trans-PRK group and 0.98 ± 0.12 in the FS-LASIK group (p < 0.001), and corresponding safety index values were 0.96 ± 0.13 and 0.99 ± 0.12 (p < 0.001). Distance from target refraction was 0.45 ± 0.42 D in Trans-PRK group and 0.43 ± 0.38 D in the FS-LASIK group (p = 0.537); 71.6% and 74.2% of eyes were within ±0.5 D of attempted correction, respectively (p = 0.193). CONCLUSIONS: Both Trans-PRK and FS-LASIK demonstrated excellent results, mostly comparable with the current literature. FS-LASIK achieved better results than Trans-PRK surgery in the efficacy and safety parameters.