Laser In Situ Keratomileusis Procedure Research Articles

Fitting-Shape-based Strategy for Topography-guided LASIK: A Prospective Study.

To assess and compare the visual acuity and refractive outcomes of topography-guided laser in situ keratomileusis (LASIK) based on the fitting-shape-based refractive compensated and Phorcides software strategies. Consecutive patients who underwent topography-guided LASIK were included in this study. Through double-masked simple randomization, patients were assigned to the Zhang & Zheng Auto-compensate Refraction (ZZ AR) group (the fitting-shape-based refractive compensated strategy using the ZZ AR calculator was used) or the Phorcides group (the topography analysis algorithm in Phorcides software [Phorcides LLC] was used). Only one eye per patient with binocular correction was randomly enrolled. The preoperative and postoperative visual acuities and refraction were analyzed at the 6-month follow-up visit. The ZZ AR and Phorcides groups comprised 156 and 147 eyes, respectively. At the 6-month postoperative follow-up visit, the median (range) absolute residual cylindrical refraction was 0.35 (1.01) and 0.47 (1.63) diopters (D) for the ZZ AR and Phorcides groups, respectively (P < .001). The percentages of patients with residual cylindrical power within 0.25 D were 29.49% and 13.61% for the ZZ AR and Phorcides groups, respectively (P = .001). Based on the percentages of patients with residual cylindrical powers within 0.50 and 1.00 D, the ZZ AR group showed better outcomes (P = .02 and .01). The percentage of patients with visual acuity better than 20/16 was significantly higher for the ZZ AR group than for the Phorcides group (P = .03). The fitting-shape-based refractive compensated strategy for topography-guided LASIK procedures can better optimize the visual acuity and astigmatic refraction than the Phorcides software strategy. [J Refract Surg. 2024;40(5):e336-e343.].

Incidence of Microfolds Using a Standardized Three-Stage LASIK Flap Replacement Protocol.

To describe a standardized three-stage flap replacement protocol and report the incidence of microfolds after femtosecond laser-assisted laser in situ keratomileusis (LASIK) surgery. A retrospective analysis of 14,374 consecutive LASIK procedures with the VisuMax femtosecond laser (Carl Zeiss Meditec) by two surgeons was conducted. As per the standardized procedure, all eyes underwent the three-stage flap replacement protocol consisting of controlled standardized minimal irrigation and flap repositioning after ablation, followed by fluorescein-controlled slit-lamp adjustments and slit-lamp adjustments on day 1 (if required). Microfold incidence was recorded at all subsequent visits and recorded by independent observers classified using a standardized 6-point grading system including whether they were refractively or visually significant. Flap thickness used was 80 to 89 µm (7.2%), 90 to 99 µm (51.7%), 100 to 109 µm (17.8%), and 110 to 130 µm (23.2%). Slit-lamp adjustment at day 1 was performed in 956 eyes (6.77%), with the highest incidence in 80 to 89 µm flaps (27.6%). A flap slip occurred in 23 eyes (0.16%) and was managed at the slit lamp for 21 eyes and in the operating room for 2 eyes. At 3 months after surgery, trace microfolds were present in 158 eyes (1.10%), grade 1 in 26 eyes (0.184%), and grade 2 in 2 eyes (0.016%). Grade 1 microfold incidence per flap thickness group was 39.1% for 80 to 89 µm, 30.4% for 90 to 99 µm, 13% for 100 to 109 µm, and 17.4% for 110 to 130 µm. No eyes required a flap lift for microfolds in the operating room. Multivariate regression analysis found microfold incidence to be higher for thinner flaps, higher correction, and larger optical zone. The three-stage protocol for flap positioning and management resulted in a low incidence of clinically visible microfolds and no visually significant microfolds. Day 1 slit-lamp adjustment was required more frequently in ultra-thin 80 to 89 µm flaps. [J Refract Surg. 2023;39(6):388-396.].

Corneal Sensitivity and Patient-Reported Dry Eye Symptoms in a Prospective Randomized Contralateral-Eye Trial Comparing Laser In Situ Keratomileusis and Small Incision Lenticule Extraction

To prospectively compare corneal sensation and patient-reported symptoms of dry eye in individuals undergoing laser in situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE). Prospective randomized contralateral-eye clinical trial. 80 eyes of 40 patients with myopia at Byers Eye Institute at Stanford University were randomized to receive wavefront-guided femtosecond LASIK in one eye and SMILE in the fellow eye. Cochet-Bonnet esthesiometry was performed to assess corneal sensitivity preoperatively and at the 1-, 3-, 6-, and 12-month postoperative visits. Participants also completed questionnaires at each visit to determine the Ocular Surface Disease Index (OSDI). Eyes that underwent LASIK compared to SMILE demonstrated more corneal denervation at the postoperative 1-month (mean 2.1 vs 3.6 cm, P < .001), 3-month (3.5 vs 5.4 cm, P < .001), and 6-month (4.7 vs 5.7 cm, P < .001) visits. At the 12-month visit, both groups had returned to baseline corneal sensitivity (5.9 vs 5.9 cm, P=.908). There was no difference in OSDI between the 2 groups at any visit. Mean OSDI improved from the preoperative to the postoperative 12-month visit in both LASIK (15.3 to 8.6, P=.020) and SMILE (15.1 to 9.5, P=.029) groups. LASIK resulted in greater corneal denervation compared to SMILE in the early postoperative period, though this difference was no longer apparent after 12 months. Despite this, there was no difference in self-reported dry eye symptoms between the 2 groups. Patient-reported dry eye symptoms improved after both LASIK and SMILE procedures.

Effects of Laser In Situ Keratomileusis and Small-Incision Lenticule Extraction on Corneal Biomechanical Behavior: A Finite Element Analysis.

Myopia, which is the result of the uncoordinated development of the eyeball, has become a major public health focus worldwide. Laser in situ keratomileusis (LASIK) and small-incision lenticule extraction (SMILE) have been successfully used in modern corneal refractive surgery. However, there are still controversies about postoperative results of LASIK and SMILE. In this study, a three-dimensional finite element model of the cornea was constructed based on the elevation and pachymetry data of a female volunteer. Surgical parameters, magnitudes of myopic correction, and intraocular pressure (IOP) were varied. Furthermore, an iterative algorithm was applied to retrieve the free-stress state of the intact corneal model, LASIK model, and SMILE model. To better evaluate the differences between LASIK and SMILE procedures, the displacement and Von Mises stress on the anterior and posterior corneal surface along the x- and y-axes were analyzed. Results for the zero-pressure model showed larger displacement compared to the image-based corneal model, suggesting that the initial corneal pre-stress stiffens the response of the cornea, both in the intact cornea and under refractive surgery. In addition, the displacement on the corneal surface in LASIK (both zero-pressure and image-based model) was obviously higher than that of the SMILE model. In contrast, SMILE increased Von Mises stress in the corneal cap and reduced Von Mises stress in the residual stromal bed compared with the LASIK model. However, the maximum Von Mises stress in the SMILE model was still smaller than that of the LASIK model. Moreover, the displacement and Von Mises stress on the residual stromal bed increased linearly with IOP. Overall, LASIK and SMILE refractive surgery could change biomechanical behaviors of the cornea. Compared to LASIK refractive surgery, SMILE may present a lower risk of ectasia. Creating a corneal cap rather than a corneal flap may have an advantage in improving corneal biomechanical stability.

Effect of photorefractive keratectomy versus laser in situ keratomileusis on corneal hysteresis in moderate myopic eyes

IntroductionAblation procedures used for vision correction such as photorefractive keratectomy (PRK) or laser in situ keratomileusis (LASIK) flap creation produce massive changes within the corneal structure and biomechanical properties. These changes are due to thinning of the central cornea and disruption of continuity of the collagen lamellae. Several approaches to assessment of the biomechanical properties have been proposed. Refractive photoablation procedures that decrease corneal hysteresis (CH) and corneal resistance factor (CRF) have been shown by several studies; therefore, here in our study we are going to discuss the effect of PRK versus LASIK on the corneal biomechanics and stability over time.AimTo compare the postoperative biomechanical properties of the cornea after PRK and after LASIK in eyes with moderate myopia.Patients and methodsThe study is 'prospective, controlled, and randomized.' In all, 40 eyes with moderate myopia (−2.0 to − 5.0 D) underwent refractive correction of myopia; 20 of them (group A) were enrolled for PRK while the other 20 of them (group B) were enrolled for LASIK surgery. CH and CRF were measured with an ocular response analyzer preoperatively and 1and 3 months postoperatively. All eyes were subjected to corneal topography preoperatively and 1 and 3 months postoperatively ocular response analyzer was used preoperatively and 1 and 3 months postoperatively.ResultsAll patients were followed up postoperatively at 1 and 3 months. The CH and CRF were measured in both groups preoperatively and postoperatively. In group A, the mean preoperative CH was 10.7 ± 0.4 (range: 10–11.1) and CRF was 10.2 ± 0.11 (range: 10.1–10.5), whereas in group B it was 10.57 ± 0.38 (range: 10–11.2) and the CRF was 10.21 ± 0.1 (range: 10–10.5), respectively, with no significant difference (P = 0.43 and 0.25, respectively).After 1 month, CH and CRF were 8.4 ± 0.27 (range: 7.9–9.1) and 8.2 ± 0.23 (range: 7.8–8.6) in group A and 8.3 ± 0.25 (range: 8.0–9.0) and 8.17 ± 0.19 (range: 7.9–8.5) in group B, respectively, with no significant difference (P = 0.28 and 0.45, respectively). At 3 months, CH and CRF were 8.6 ± 0.28 (range: 8.1–9.2) and 8.3 ± 0.21 (range: 7.8–8.6) in group A and 8.55 ± 0.26 (range: 8.2–9.1) and 8.28 ± 0.18 (range: 7.9–8.6) in group B, respectively, with no significant difference (P = 0.56 and 0.32, respectively). The corneal biomechanical parameters decreased after both PRK and LASIK procedures. The corneal biomechanical parameters decreased after both PRK and LASIK procedures. The postoperative measurements of CH and CRF at 3 months were lower than the preoperative values in both groups with a significant amount (P < 0.001).ConclusionBoth PRK and LASIK substantially weaken the biomechanical strength of the cornea, the greater the amount of myopic correction, the more the change in corneal biomechanics.

Late onset of microbial keratitis after laser in situ keratomileusis surgery: case series.

To report predisposing factors, clinical features, microbiology spectrum, antibiotic resistance, antimicrobial therapy, and outcomes of patients with a previous laser in situ keratomileusis (LASIK) surgery and diagnosed with presumed microbial keratitis. Sydney Eye Hospital, Sydney, New South Wales, Australia. Retrospective case review. Patients were identified from pathology and hospital coding data from 2012 to 2016. Inclusion criteria were all patients with a previous LASIK surgery, a presumed diagnosis of microbial keratitis, and a corneal scrape performed and aged older than 18 years. Demographics, clinical details, and outcomes were collated from the medical records. Sixteen patients were included, with median age of 41.5 years (range 22 to 85 years) and 56.2% of women. The median time between LASIK procedure and microbial keratitis presentation was 38.3 months (interquartile range 6.7 to 77.45 months). Cultures were positive for bacteria in 12 (75%) of 16 scrapes. Of the bacterial isolates, 12 (85.7%) were gram-positive and 2 (14.3%) gram-negative. Sensitivity profiles for the isolated bacteria were similar between fortified antibiotics (cefalotin and gentamicin) and commercial products (chloramphenicol and ofloxacin). Complications included the need for tectonic grafts, nonhealing epithelial defects, thinning, and neovascularization. Late onset of keratitis after LASIK can occur with no positive cultures for nontuberculous mycobacteria, no interface involvement, and no other usual features reported in case series of infectious keratitis in LASIK patients. It has a similar clinical course to non-LASIK keratitis, such that the surgery may not have been a risk factor for infection.

Effect of suction on the posterior segment after LASIK using Femtosecond Laser vs Microkeratome

Background: Creating a successful corneal flap is the first critical step during LASIK surgery. Two techniques are used to produce corneal flaps during LASIK surgery: a microkeratome or a femtosecond laser. Femtosecond laser has a significant impact on refractive surgery by enabling non-mechanical creation of corneal flaps during laser in situ keratomileusis (LASIK). During LASIK flap creation, intraocular pressure (IOP) increases to levels exceeding 65 mm Hg. Femtosecond laser flap creation exerts less extreme IOP fluctuations but requires more procedural time than when a microkeratome is used. This study was conducted upon 60 eyes of 38 patients to evaluate the effect of applied suction during LASIK procedures on the posterior segment of myopic eyes, whether the flap was created by Microkeratome or Femtosecond laser. The study subjects were equally divided into 2 groups: group F (30 eyes of 20 patients) underwent femtosecond laser-assisted LASIK surgery and group M (30 eyes of 18 patients) underwent microkeratome-assisted LASIK surgery using Moria M2 for the treatment of myopia. It was found that the central macular thickness and RNFL thickness were not changed significantly in both groups when measured 1 week after surgery. Regarding the incidence of PVD, there was a higher incidence in group F, it was detected in 8 eyes (26.7%) compared to group M, it was detected in 1 eye (3.3%). Conclusion: Slight localized changes of macular thickness and reduction of the RNFL thickness were caused by LASIK using the two major forms of flap creation, namely a microkeratome or a femtosecond laser. Regarding the incidence of PVD, it was found that femtosecond laser-assisted LASIK using Visumax femtosecond laser had a higher incidence than that after microkeratome-assisted LASIK with the Moria M2. So the surgery of LASIK is safe and efficient, but surgeons should choose effective and safe suction mode, shorten the suction time and exclude potential retinopathy and pre-existing glaucoma before surgery to improve the safety and efficacy of LASIK.

The effect of nerve growth factor on corneal nerve regeneration and dry eye after LASIK

Dry eye is the most common complication after refractive surgery, especially after laser in situ keratomileusis (LASIK), in which nerves may be cut when making the corneal flap. Nerve growth factor (NGF) has been demonstrated to stimulate corneal sensitivity and nerve regeneration and NGF has been suggested as a potential treatment for dry eye disease (DED). Hence, this study aimed to investigate the effect of NGF on corneal nerve regeneration, sensitivity and dry eye symptoms after LASIK, compared to hycosan and normal saline (NS) treatments. Thirty-eight New Zealand white rabbits that underwent LASIK procedures were randomly assigned to three groups. Each group underwent NGF, hycosan, and NS treatment. The nerve densities and the number of corneal sub-basal and superficial stromal nerves were measured with confocal microscopy, and the results were compared before surgery and at one month and three months postoperatively. Corneal sensitivity was assessed with an esthesiometer. The tear breakup time (TBUT) was recorded to check for signs of dry eye. The whole corneas of the experimental animals were excised at three months after the surgery for immunohistochemically analysis. After LASIK, treatment with NGF significantly accelerated the recovery of sub-basal and superficial stromal nerve densities and the numbers, compared to hycosan and NS treatments at one month and three months postoperatively (NGF vs. hycosan, P < 0.01 each; NGF vs. NS, P < 0.01 each). The recovery of corneal sensitivity was significantly enhanced in the NGF group compared to the hycosan or NS treatment groups after surgery (P < 0.05). Also, the TBUT data showed a statistically significant longer time in the NGF group at one month, and three months postoperatively (P < 0.05). Immunofluorescence analysis showed the nerve fiber quantity of the NGF group was larger than in the hycosan and NS groups. Taken together, the experimental results suggested that mNGF had an obvious effect on promoting corneal nerve repairing and the potential to improve dry eye in different periods following LASIK.

The Percent Volume Altered in Correction of Myopia and Myopic Astigmatism With PRK, LASIK, and SMILE.

To determine the volumes altered during photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) correction of myopia and myopic astigmatism. The volumes of stromal tissue affected by surgical correction of pure and astigmatic myopia were calculated in this theoretical study for PRK, LASIK, and SMILE treatments. These results were then used to calculate representative values for percent volume altered (PVA) restricted to stromal corneal tissue. For the same spherical equivalent, there were remarkable differences between the amount of tissue removed between pure and compound myopic corrections. The PVA of LASIK procedures was the largest, whereas the PVA was comparable between PRK and SMILE. PRK had the lowest PVA for low myopic and compound astigmatic corrections and SMILE had the lowest PVA for high myopic and compound myopic astigmatism procedures. The comparison of volumes of tissue removed and PVA values of different treatment modalities provided in this study may give clinicians an improved understanding about the potential influence of geometrical parameters of those methods on the biomechanics of the cornea. [J Refract Surg. 2020;36(12):844-850.].

Biology of keratorefractive surgery- PRK, PTK, LASIK, SMILE, inlays and other refractive procedures

The outcomes of refractive surgical procedures to improve uncorrected vision in patients—including photorefractive keratectomy (PRK), laser in-situ keratomileusis (LASIK), Small Incision Lenticule Extraction (SMILE) and corneal inlay procedures—is in large part determined by the corneal wound healing response after surgery. The wound healing response varies depending on the type of surgery, the level of intended correction of refractive error, the post-operative inflammatory response, generation of opacity producing myofibroblasts and likely poorly understood genetic factors. This article details what is known about these specific wound healing responses that include apoptosis of keratocytes and myofibroblasts, mitosis of corneal fibroblasts and myofibroblast precursors, the development of myofibroblasts from keratocyte-derived corneal fibroblasts and bone marrow-derived fibrocytes, deposition of disordered extracellular matrix by corneal fibroblasts and myofibroblasts, healing of the epithelial injury, and regeneration of the epithelial basement membrane. Problems with epithelial and stromal cellular viability and function that are altered by corneal inlays are also discussed. A better understanding of the wound healing response in refractive surgical procedures is likely to lead to better treatments to improve outcomes, limit complications of keratorefractive surgical procedures, and improve the safety and efficiency of refractive surgical procedures.

Accommodation Amplitude Before and After Laser In Situ Keratomiletus (LASIK) In Myopic Patients

ABSTRACT&#x0D; Introductions: Laser in situ Keratomileusis (LASIK) is the most common refractive surgery to treat myopia. One of the most common complain after this procedure is blurry near- vision.&#x0D; Objectives: To evaluate the role of accommodation amplitude (AA) in myopic patients before and after LASIK and its effect to blurry near-vision in myopic patients after LASIK&#x0D; Methods: Patients with myopia who underwent LASIK procedure in Sriwijaya Eye Center Hospital from January to February 2018 studied prospectively. AA was assessed before and after LASIK with 1 day, 1 week and 1 month. Myopia degree, intraocular pressure (IOP), age, gender, ablation and corneal profile were also assessed.&#x0D; Results: A total 52 eyes from 32 patients were included. Visual acuity (VA) of all sample were significantly improve in 1 day after LASIK (p 0,001). Mean AA in myopic patients before LASIK 9,25 D and AA 1 day after LASIK were all significantly decrease into 9,00D (p 0,012) which can cause in blurry near- vision after LASIK. In 1 month followed-up, mean AA is significantly improved into 11,00 D (p 0,000) with no complain. Other factor that affect the changing AA were corneal cell density (CD), IOP and AA before LASIK.&#x0D; Conclusions: There is significant AA difference in myopic patients before and after LASIK. Blurry near-vision after LASIK is caused by AA adaptation mechanism after LASIK.

Prediction accuracy of IOL calculation formulas using the ASCRS online calculator for a diffractive extended depth-of-focus IOL after myopic laser in situ keratomileusis.

To evaluate IOL calculation formulas provided by an online calculation tool from the ASCRS for an extended depth-of-focus (EDOF) IOL after previous myopic laser in situ keratomileusis (LASIK). Department of Ophthalmology, Goethe University, Frankfurt, Germany. Retrospective consecutive case series. Patients who underwent cataract surgery or refractive lens exchange with implantation of a diffractive EDOF IOL and who had a history of myopic LASIK were included. Biometry, refractive data regarding the LASIK procedure, target refraction, and postoperative refraction were collected. Mean prediction error, mean absolute error (MAE), and the number of eyes within ±0.5 diopters (D), ±1.0 D, ±1.5 D, and ±2.0 D were calculated with the following formulas from the ASCRS calculator: Shammas, Haigis-L, Barrett True-K, Barrett No History, Masket, modified Masket, and the average of all formulas (average). Twenty-five eyes matched the inclusion criteria. Mean spherical equivalent (SE) was -0.81 ± 0.69 D; the mean pre-LASIK SE was -6.4 ± 3.63 D. The formulas ranked by MAE were Shammas (0.7 ± 0.75 D), Haigis-L (0.72 ± 0.57 D), average (0.79 ± 0.8 D), Barrett True-K (1.14 ± 0.89 D), modified Masket (1.4 ± 1.15 D), Barrett No History (1.45 ± 0.7D ), and Masket (1.64 ± 1.27 D). The formulas with the most eyes within ±0.5 D were average (52%), Shammas (48%), and Haigis-L (44%) formulas. Calculation of IOLs in eyes with a history of refractive surgery remains a challenge. In this study, the Shammas and Haigis-L formulas performed best regarding MAE and percentage of eyes within ±0.5 D; however, the average of all formulas delivered reasonable results.

Does Pregnancy Affect Refractive and Corneal Stability or Corneal Epithelial Remodeling After Myopic LASIK?

To investigate possible refractive changes in pregnant women who have previously undergone myopic laser in situ keratomileusis (LASIK). This prospective study included 64 pregnant women (128 eyes) who had previously undergone bilateral myopic LASIK. Uncorrected distance visual acuity (UDVA), spherical equivalent, corneal keratometry, topography and tomography, and epithelial mapping were evaluated before LASIK, 12 months after LASIK, during the third trimester of pregnancy, and 1 year postpartum. The average age at the time of recruitment was 32.5 ± 5 years (range: 24.5 to 39.5 years). The evaluation during pregnancy was at an average 55 months (range: 12 to 108 months) from the initial LASIK procedure. The preoperative mean refractive error was -6.72 ± 2.96 diopters (D) (range: -1.00 to -11.00 D). Comparing 12-month refractive data after the original LASIK procedure to the those within the third trimester of the subsequent pregnancy, the average UDVA was 20/18, the residual refractive error was -0.63 ± 1.00 to -0.51 ± 0.82 D, the steepest keratometry value was 40.85 ± 1.89 to 40.88 ± 2.84 D, and the central epithelial thickness was 56.4 ± 3.89 to 57.38 ± 5.04 µm, respectively. In this study, pregnancy did not affect the refractive stability of LASIK. Pregnancy-related changes in refractive error, corneal stability, and total corneal and epithelial thickness in women after LASIK were not found to be statistically significant. [J Refract Surg. 2022;36(2):118-122.].

Neuroprotective Effect of Citicoline Eye Drops on Corneal Sensitivity After LASIK.

To evaluate the accelerator role of a topically administered neuroprotective eye drop (citicoline) on the recovery of corneal sensitivity after laser in situ keratomileusis (LASIK). In this prospective, controlled study, 78 eyes of 78 patients (mean age: 26.8 ± 7.6 years) were enrolled in the study group and their eyes were treated with topical citicoline three times a day for 1 month postoperatively. Seventy-eight eyes of 78 patients (mean age: 26.1 ± 7.4 years) were randomly selected as the control group and their eyes were treated with lubricant hyaluronic acid (0.15%) eye drops three times a day for 1 month. Corneal sensitivity was assessed in both groups using a Cochet-Bonnet esthesiometer at baseline and 1, 2, 3, 4, 6, 8, and 12 weeks after the LASIK procedure. Corneal sensitivity at 1, 2, 3, 4, and 6 weeks after LASIK was significantly better in the citicoline group than the control group (P < .05 for all). Differences between the groups at 8 and 12 weeks after LASIK were not significant (P > .05). Topically administered citicoline eye drops had beneficial effects in the early recovery of corneal sensitivity during the first 6 weeks after LASIK, suggesting that citicoline may play a significant role in accelerating corneal reinnervation. [J Refract Surg. 2019;35(12):764-770.].

Laser flap enhancement 5 to 9 years and 10 or more years after laser in situ keratomileusis: Safety and efficacy

To study the safety and efficacy of refractive enhancement by flap lifting 5 and 10 years after laser in situ keratomileusis (LASIK). Vissum Alicante, Spain. Retrospective case series. Eyes with a flap lift at least 5years after primary LASIK with a 3-month follow-up were evaluated. The primary outcome measures were safety and the complication rate. Moderate epithelial ingrowth was managed with Nd:YAG laser treatment. The primary LASIK procedure was myopic in 45 eyes, hyperopic in 22 eyes, and presbyopic in 3 eyes. The mean time from primary LASIK to the flap lift was 12.3years±3.45 (SD). In 57 eyes, the primary LASIK flap was created at least 10years before the enhancement. The mean pre-lift spherical equivalent was -1.29±1.23 diopters (D) in the myopia group and +0.65±1.72 D in the hyperopia group. Three months later, 88% of eyes and 74% of eyes, respectively, had an uncorrected distance visual acuity of 20/20 or better; 100% achieved at least 20/25. No eye lost 2 lines or more of corrected distance visual acuity. In the myopia group, the efficacy index was 0.94 and the safety index was 0.98 at 6months. Mild epithelial ingrowth developed in 31.43% of eyes and clinically significant epithelial ingrowth in 11.42% of eyes; 4.28% required a relift for severe epithelial ingrowth. Late flap lift for refractive enhancement 10years or more after LASIK provided good efficacy and safety with fast visual recovery. The rate of surgical intervention for significant postoperative epithelial ingrowth was low.

Post-laser in-situ keratomileuses effects on visual field in myopia and myopic astigmatism

BackgroundThe suction used during the laser insitu keratomileusis (LASIK) procedure necessary for cutting of the cornea by an oscillating blade induces an increase of intraocular pressure (IOP) to approximately 60 mm Hg or even more. This acute increase in IOP during LASIK may endanger the blood flow within the retinal vessels and induce visual field (VF) depression. PurposeTo identify the effect of LASIK on the visual field parameters. SettingsProspective interventional case series study performed in ELNOOR ophthalmology center. From October 2015 to October 2016. MethodsProspective interventional case series study including patients with myopia and myopic astigmatism who were deemed candidates for LASIK correction. All recruited patients underwent visual field examination immediately before,1 week and 3 months post LASIK using Humphrey 750 Visual Field Analyzer (Zeiss Humphrey Systems, San Leandro, CA, USA), with a white-on-white Swedish Interactive Threshold (SITA). LASIK procedure was done using Allegretto device (wave light EX500, ALCON, Fort Worth, TX, USA) and Moria microkeratome (MM2). Results60 eyes of 30 patients were included in our study. Mean age was 28 + 5.6 years (range20-41), mean spherical equivalent (S.E) was -6.1 + 3.2 D (Range -1.4 to -15.1D), mean axial length was 23.5 + 1.5mm (Range 21-26.3mm). Humphrey global indexes included MD and PSD. The MD index estimates the uniform part of VF deviation, while the PSD index estimates the non-uniform part of VF deviation, reflecting the amount of localized depression of the VF. We found that (MD) shows slight decrease 1-week postoperative which is statistically significant, then improved 3 months postoperative with no statistical significant difference between preoperative and 3 months postoperative values. As regards PSD we found that there is no statistical difference between preoperative,1 week and 3 months postoperative. ConclusionThe surgery of LASIK is safe and efficient, but surgeons should choose effective and safe suction mode, shorten the suction time and exclude potential retinopathy and preexisting glaucoma before surgery to improve the safety and efficacy. We found that LASIK procedure has no significant effect on visual field parameters, except for diffuse depression that occurs in the first week postoperative.

Lasik as a Solution for High Hypermetropia.

Aim:To evaluate safety and efficacy of Laser in situ Keratomileusis (LASIK) procedure for the correction of high hypermetropia.Methods:Retrospective study of 160 patients (266 eyes) who underwent LASIK procedure for the correction of hypermetropia between +3.00 and +7.00 diopters(D) and cylinder up to 2.00D from January 2013 and August 2015. All ablations were performed with Wavelight Allegretto Eye-Q400Hzexcimer laser (Alcon, Forth Worth, TX, USA) with aberration free module and were centered on a corneal vertex. All flaps were made with Moria M2 (Moria, Antony, France) mechanical microkeratome (90μm head). Preoperative and postoperative uncorrected and corrected distant visual acuity (UDVA, CDVA), spherical equivalent (SE) and a berrometry for 5mm pupil were measured. Measurements were taken at 1 week, 1,3,6 and 12 months after the surgery. Wilcoxon Signed Ranks Test was used for statistical analysis.Results:Postoperative UDVA was lower than preoperative CDVA at 1 week(p=0.001), at 1 month there was no difference (p=0.099), and at 3,6 and 12 months UDVA was better (p<0.0001). Preoperative SE was 4.69±1.20D (+3.75 to +7.50D). At 1 week SE was 0.03±0.67D (-0.50 to +0.63D), while at 1 year regressed to 0.58±0.56D (+0.25 to +0.88D). Sphere shifted from negative values targeted in treatment planning to compensate for regression to positive values. There was significant difference in SE at every time point (p<0.0005). There was a significant increase in coma (p<0.0001), trefoil (p<0.0001, p=0.0006) and spherical aberration (p=0.022, p=0.0052) at 1 week and 1 month postoperatively, without change throughout the rest of follow up.Conclusion:LASIK for high hypermetropia showed satisfactory results in postoperative refraction with reasonable regression without significant loss of lines of visual acuity. However, more test are necessary to asses optical quality.

Comparison of Corneal Epithelial Remodeling Over 2 Years in LASIK Versus SMILE: A Contralateral Eye Study.

To evaluate 3-dimensional epithelial remodeling in patients undergoing myopic laser in situ keratomileusis (LASIK) versus small incision lenticule extraction (SMILE). In a prospective randomized contralateral eye study of LASIK versus SMILE procedures, 21 consecutive patients (42 eyes) were evaluated with corneal epithelial mapping by anterior segment optical coherence tomography for up to 2 years. In the LASIK group, central epithelial thickness increased from 52.38 ± 2.57 μm to 57.00 ± 4.23 μm and remained almost stable at this level for up to 24 months. In the SMILE eyes, it increased from 52.52 ± 3.01 μm to 57.15 ± 4.57 μm and also remained stable for up to 24 months. Both techniques created the same level of epithelial thickness increase and variation, with a significantly higher mid-peripheral epithelial thickness increase. The differences between the preoperative and postoperative changes were found statistically significant, but not different between the 2 techniques at any given time studied. Both LASIK and SMILE resulted in significant epithelial thickening. This response seemed to be surprisingly quite similar between the 2 different techniques. This study suggests that epithelial remodeling may correlate with relative curvature changes resulting after both techniques, rather than the obvious difference of subepithelial corneal denervation changes.

Nd:YAG laser for epithelial ingrowth after laser in situ keratomileusis.

To evaluate the efficacy of neodymium:yttrium-aluminum-garnet (Nd:YAG) laser for treatment of epithelial ingrowth after laser in situ keratomileusis (LASIK). Fifty-eight patients with epithelial ingrowth presented to Sohag refractive center, Sohag, Egypt, between January 2015 and March 2017. Only 41 patients (18 females and 23 males, mean age: 33.4years) involving 41 eyes were indicated for treatment by Nd:YAG laser as the rest of the eyes were only under observation. Patients with epithelial ingrowth were recognized at a mean of 6months after primary LASIK procedure (range: 2-16months). Four eyes had undergone previous LASIK enhancements. Four eyes had the epithelial ingrowth removed by flap lift and scrapping. The mean intensity of the spots used was 0.8mJ with variable number of shots depending on the size and density of the epithelial ingrowth area. Twenty-eight eyes showed complete regression after one session, while the rest necessitated 2-3 sessions for complete resolution. Mean follow-up period was 8months (range 5-12months). Epithelial ingrowth was treated successfully in all 41 eyes. The uncorrected visual acuities were 20/20, and there was no evidence of recurrent epithelial ingrowth after 6months with no complications reported. YAG laser is a simple, effective outpatient procedure for the management of epithelial ingrowth after LASIK.

Investigation of the Changes in Refractive Surgery Trends in Korea.

PurposeTo evaluate changes in clinical practice in the field of refractive surgery in Korea over the past 10 years.MethodsA survey consisting of 59 multiple-choice questions regarding the preferred types of refractive surgery, excimer laser machine, and presbyopia surgery was mailed to 742 members of the Korean Society of Cataract and Refractive Surgery in January 2016, and 50 members responded to the survey. These data were compared with the 2005 or 2007 survey results.ResultsThe majority of respondents were in their 40s (54%), and the average number of refractive surgeries performed in one month was 53. The most commonly used excimer laser machine was the VISX S4 in both 2005 (32%) and 2015 (25%); however, a greater variety of machines (EX500 [18%], Allegretto wave Eye-Q [13%], AMARIS 750 [10%]) were used in 2015. The preferred corneal refractive surgery in 2015 was surface ablation (40%), representing a significant increase in its popularity compared to 2005 (15%) (p < 0.001). The popularity of laser in situ keratomileusis (LASIK) surgery decreased to 20% in 2015 compared to 48% in 2005 (p < 0.001). Eighty percent of LASIK procedures in 2015 were performed using femtosecond laser. In 2015, surface ablation and phakic intraocular lens implantation were preferred for the treatment of myopia less than -8 diopters and more than -8 diopters, respectively. The proportion of respondents performing presbyopia surgery in 2015 (76%) was significantly increased from 2007 (30%) (p < 0.001).ConclusionsOver the past decade, the most commonly performed corneal refractive surgery has changed from LASIK to surface ablation, and there has been a significant increase in the popularity of presbyopia surgery.