Residual Stromal Bed Research Articles

Residual stromal bed thickness correlates with regression of myopia after LASIK.

PurposeThe purpose of this study was to evaluate the correlation between residual stromal bed thickness (hereinafter bed thickness) and regression of myopia after LASIK, taking into consideration the long-term outcomes.Subjects and methodsA total of 177 patients (309 eyes) and 41 patients (70 eyes) were retrospectively reviewed at 5 and 10 years after surgery, respectively. These patients were also continuously examined throughout the study. All patients underwent laser in situ keratomileusis (LASIK) for myopia in our clinic and scored at least 1.0 (0 logMAR) uncorrected distance visual acuity (UCVA) 1 month after surgery. Bonferroni–Dunn method and Student’s t-test were used for statistical analyses.ResultsCases with a refractive value (spherical equivalent) of less than −6.0 D (Group A) were compared to those with −6.1 D or higher (Group B). There was a statistically significant decrease in Group B UCVA of 0.04 logMAR and 0.12 logMAR at 5 and 10 years after surgery, respectively. With regard to the relationship between regression of myopia and bed thickness in the long-term, there was a significantly higher frequency of regression of myopia in cases with less than 350 μm bed thickness compared to those with 350 μm and more, in a surgical volume of more than −6.1 D (Group B).ConclusionThe present study indicates that bed thickness correlates with regression of myopia after LASIK and enough bed thickness is important to maintain good UCVA in the long-term.

Short-term Variance of Refractive Outcomes After Simultaneous LASIK and High-Fluence Cross-linking in High Myopic Correction.

To analyze the visual and refractive outcomes of LASIK with and without simultaneous cross-linking for correction of myopia. Patients who received femtosecond laser-assisted LASIK with and without adjunctive cross-linking according to patient's preference were examined longitudinally for 6 months. Patients with myopic manifest refraction spherical equivalent of 5.00 diopters (D) or greater and estimated residual stromal thickness of greater than 250 µm were included. Overall, 120 eyes of 60 patients were included (60 eyes of 30 patients for LASIK with cross-linking; 60 eyes of 30 patients with LASIK only). No significant difference was observed in age, preoperative corrected distance visual acuity, manifest refraction spherical equivalent, manifest sphere and cylinder, minimal corneal thickness, and residual stromal bed thickness between both groups (P ≥ .245). The uncorrected distance visual acuity and efficacy index were significantly worse on day 1 in eyes receiving adjunctive cross-linking (P = .0001). At 6 months, 86.7% and 95% of the eyes achieved uncorrected distance visual acuity of 20/25 or better in LASIK with cross-linking and LASIK only, respectively. The variance of postoperative spherical equivalent and sphere was significantly higher in eyes undergoing LASIK with cross-linking from 1 week up to 6 months compared to LASIK only (P ≤ .002). None of the patients required re-treatment up to 6 months postoperatively. Adjunctive cross-linking during LASIK was associated with worse visual outcomes during the first postoperative week. The variance of spherical equivalent was also high in these patients over a 6-month follow-up. [J Refract Surg. 2016;32(10):664-670.].

Comparison of Two Cap Thickness in Small Incision Lenticule Extraction: 100μm versus 160μm.

PurposeTo compare the changes of biomechanical properties, endothelial cell density (ECD), and posterior corneal elevation (PCE) after femtosecond small incision lenticule extractions (SMILEs) with 100μm versus 160μm cap thicknesses.MethodsA total of 12 rabbits were randomly assigned into two groups of 6 each. SMILE was performed at a depth of either 160μm (160-cap group) or 100μm (100-cap group). Corneal biomechanics, PCE, ECD were evaluated pre-operatively, 1week, 1 month, 2 months, 3 months, and 4 months post-operatively by Pentacam, Corvis ST, in vivo confocal microscopy (IVCM) respectively. The Young’s modulus was obtained by strip-extensometry test 4 months after surgery.ResultsAt each time point, the second applanation time (A2T) was similar between the groups with the exception of 4 months after surgery (22.66±0.16 ms in the 160-cap group versus 21.75±0.29 ms in the 100-cap group, p = 0.004). Neither deformation amplitude (DA) nor the first applanationtime (A1T) were significantly different between the two groups. The postoperative posterior surface did not shift forward, the changes of PCE and ECD were not significantly different between the two groups at any observation time. Young’s modulus was higher in the 160-cap group than that in the 100-cap group with no statistical significance (P>0.05). Regression analyses showed that the PCE changes and Young’s modulus were not affected by cap thickness (CT) or residual stromal bed thickness (RBT) (All P>0.05).ConclusionsThe differences of corneal biomechanics, posterior surface elevation, or ECD changes were quite small when using 100μm or 160μm cap thicknesses in SMILE.

Percent tissue altered and corneal ectasia.

This article reviews the association of a novel metric, percentage tissue altered (PTA), with the occurrence of ectasia after laser in-situ keratomileusis in eyes with normal corneal topography, and analyses the influence of the variables that comprise it, and its role on eyes with suspicious topography. PTA is derived from [PTA = (FT + AD)/CCT] where FT = flap thickness, AD = ablation depth, and CCT = preoperative central corneal thickness. Our studies revealed that there is a robust relationship between high PTA and ectasia risk in eyes with normal preoperative topography. PTA higher or equal to 40% presented the highest odds ratio and highest predictive capabilities for ectasia risk than each of the variables that comprise it, residual stromal bed or age. Average thicker flaps alone were insufficient to create ectasia unless coupled with greater ablation depths, meaning a high PTA. In eyes with suspicious topography, even low PTA value is sufficient to induce ectasia. This new metric, PTA, should be taken into account when screening patients for refractive surgery. Patients with normal topography or tomography, presenting a PTA higher or equal to 40% should be considered at higher risk for post laser in-situ keratomileusis ectasia.

Prevention of Iatrogenic Keratectasia.

Iatrogenic corneal ectasia is a rare but devastating complication after refractive surgery. While its incidence appears to be declining, it has not been eliminated. Its cause is probably related to a combination of an intrinsic predisposition to ectasia and an additional anatomical destabilising effect from the refractive surgery. Determining which eyes are intrinsically "weak" and exactly how much additional "weakening" an eye can withstand before developing progressive thinning and protrusion are both difficult tasks. The essentially universal availability of corneal topography and the increasing use of corneal tomography have significantly improved our ability to preoperatively diagnose early forms of corneal ectasias, especially keratoconus and pellucid marginal degeneration. Advanced software algorithms have also enhanced the sensitivity and specificity of these technologies. Newer technologies, such as measuring corneal biomechanics and corneal epithelial distribution, will hopefully continue to help us to differentiate normal from abnormal corneas preoperatively. In addition to abnormalities in anterior and posterior corneal curvature, a number of other risk factors for the development of post-refractive surgery ectasia have been proposed, including younger patient age, thinner central corneal thickness, thinner residual stromal bed thickness and high myopia. If the percentage of altered tissue is > 40 %, this is an extremely accurate predictor of corneal ectasia after refractive surgery. While there are a number of effective treatments for iatrogenic corneal ectasia, such as contact lenses, corneal crosslinking, intracorneal rings and corneal transplantation, prevention should be the goal. With newer and better corneal imaging technology to help screen out patients with abnormal corneas along with an improved understanding of exactly how much weakening a given cornea can take, we should be able to minimize this vision threatening complication.

Application of corneal tomography before keratorefractive procedure for laser vision correction.

Ectasia after refractive surgery represents a major concern among refractive surgeons. Corneal abnormalities and preexisting corneal ectasia are the most important risk factors. Corneal topography and central corneal thickness are the factors traditionally screening for in refractive surgery candidates. Study of the anterior surface by Placido topography allows for identification of keratoconus before biomicroscopy. However, this is insufficient for the evaluation of pre-operative refractive surgery. There are cases of ectasia after laser in situ keratomilusis (LASIK) without identifiable risk factors such that there is a need to go beyond the corneal surface. A key requirement is quantifying susceptibility to corneal biomechanical instability and progression to ectasia. Tomographic indices derived from elevation maps and pachymetry spatial variation produce a Belin Ambrosio display final D index (BAD-D index), which has shown better results compared to surface curvature indices for detecting very mild forms of ectasia. A logistic regression formula, integrating age, residual stromal bed, and BAD-D (Ectasia Susceptibility Score, ESS) resulted in a significant improvement in accuracy, leading to 100% sensitivity and 94% specificity for detecting susceptible cases. A comprehensive corneal structural analysis based on corneal segmental tomography can detect susceptible corneas, which increases safety for refractive surgery patients.

Ectasia risk factors in refractive surgery

This review outlines risk factors of post-laser in situ keratomileusis (LASIK) ectasia that can be detected preoperatively and presents a new metric to be considered in the detection of ectasia risk. Relevant factors in refractive surgery screening include the analysis of intrinsic biomechanical properties (information obtained from corneal topography/tomography and patient’s age), as well as the analysis of alterable biomechanical properties (information obtained from the amount of tissue altered by surgery and the remaining load-bearing tissue). Corneal topography patterns of placido disk seem to play a pivotal role as a surrogate of corneal strength, and abnormal corneal topography remains to be the most important identifiable risk factor for ectasia. Information derived from tomography, such as pachymetric and epithelial maps as well as computational strategies, to help in the detection of keratoconus is additional and relevant. High percentage of tissue altered (PTA) is the most robust risk factor for ectasia after LASIK in patients with normal preoperative corneal topography. Compared to specific residual stromal bed (RSB) or central corneal thickness values, percentage of tissue altered likely provides a more individualized measure of biomechanical alteration because it considers the relationship between thickness, tissue altered through ablation and flap creation, and ultimate RSB thickness. Other recognized risk factors include low RSB, thin cornea, and high myopia. Age is also a very important risk factor and still remains as one of the most overlooked ones. A comprehensive screening approach with the Ectasia Risk Score System, which evaluates multiple risk factors simultaneously, is also a helpful tool in the screening strategy.

Long-term evaluation of eyes with central corneal thickness

PurposeTo study long-term refractive and visual outcomes of laser in situ keratomileusis (LASIK) in eyes with a postoperative thin central cornea.MethodsIn this retrospective observational case series, we studied 282 myopic eyes with a normal preoperative topographic pattern and postoperative thin corneas (<400 μm) that had at least 3 years of follow-up after LASIK in three private clinics. The main outcome measures were safety, efficacy, predictability, percent tissue altered, and complications.ResultsThe mean postoperative central corneal thickness was 392.05 μm (range: 363.00–399.00 μm). After a mean follow-up of 6.89±2.35 years (standard deviation), the safety index was 1.17, the efficacy index was 0.94, and predictability (±1.00 diopter [D]) was 73.49. The mean residual stromal bed thickness was 317.34±13.75 μm (range: 275–356 μm), the mean flap thickness was 74.76±13.57 μm (range: 55–124 μm), and the mean percent tissue altered was 37.12%±3.62% (range: 27.25%–49.26%). No major complications were recorded.ConclusionLASIK with a resultant central cornea thickness <400 μm seems to be effective, safe, and predictable provided that preoperative topography is normal and the residual stromal bed thickness is >275 μm.

Greffe lamellaire endothéliale assistée au laser Excimer (ExALEK) : technique et résultats

The purpose of this study is to describe a technique for thin endothelial lamellar keratoplasty and to present the results for endothelial transplant performed at the University Hospital of Nantes. This paper is a retrospective, single-center descriptive study conducted at the University Hospital of Nantes from September 2010 to May 2014, at first for anatomical or analgesic indications (group 1) and then extended to visual indications (group 2). Patients were followed for 12 months. The preparation of the endothelial graft includes an excimer-laser ablation of the residual stromal bed after lamellar keratectomy by manual deep anterior approach. Seventy surgeries were analyzed. The etiologies were mainly Fuchs Dystrophy, secondary endothelial dystrophy and post-penetrating keratoplasty endothelial failure. Fifty-three patients were integrated in group 1 and seventeen patients in group 2. In group 1, the mean VA at 12 months was 0.70 ± 0.30 Log MAR (0.2 decimal equivalent). In group 2, the mean VA at 12 months was 0.28 ± 0.12 Log MAR (0.5 decimal equivalent). Pachymetry decreased from 740 ± 125.1 μm preoperatively to 613.4 ± 73.4 μm at 12 months. The average central thickness of the graft was 84.1 ± 28.9 μm at 1 month and 80.2 ± 29.4 μm at 12 months. The advantage of this new surgical technique is that it is a rapid and repeatable method allowing thin grafts with satisfactory functionality and easy handling. Its performance independent of the scheduled surgery, allows for predictable organization in the operating room.

Deep anterior lamellar keratoplasty using the same graft after epikeratophakia for the treatment of acute corneal hydrops in keratoconus

Objective To evaluate the clinical effects of deep anterior lamellar keratoplasty (DALK) using the same graft after epikeratophakia for the treatment of acute corneal hydrops in keratoconus. Methods A consecutive 7 cases (7 eyes) with acute corneal hydrops in keratoconus in our department were retrospectively analyzed. Same corneal graft was used to perform the first stage epikeratophakia combined with C3F8 anterior chamber injection. About 6 months after the first surgery, the secondary stage deep anterior lamellar keratoplasty combined with air anterior chamber injection was performed. The best corrected visual acuity, healing status of the anterior and posterior corneal surface, anterior segment optical coherence tomography parameters, and corneal endothelial cells density were recorded. Results The central corneal thickness was (1764±256) μm before the treatment, and it was (778±147) μm, (604±23) μm, (579±20) μm and (525±19) μm at the time points of 1 d, 7 d, 1 and 6 months after the first stage surgery respectively. An average (6.1±1.3) months after the first stage surgery, the second stage DALK was performed. The descemet's membrane at the central area could be fully exposed in 3 eyes. Slow liquid exudations in the deep corneal stroma near the descemet's membrane were found in the other 4 eyes during stroma dissection. DALKs were successfully performed in all the 7 cases. Double anterior chambers were found in 2 eyes 1d after DALK. The whole corneal thicknesses were (781±57) μm, (581±49) μm and (521±19) μm at 7 d, 1 and 3 months after DALK respectively. Three months later, the thickness of the receptors' residual stroma bed was (21±11) μm at the central corneal area. At the end of the follow-up, the BCVA(LogMAR)was 0.11±0.03. Conclusion Novel curative effect was found in the treatment of acute corneal hydrops in keratoconus by deep anterior lamellar keratoplasty using the same graft after epikeratophakia. Key words: Acute corneal hydrops, keratoconus; Epikeratophakia; Keratoplasty, deep anterior lamellar; Anterior segment optical coherence tomography; Descemet's membrane

Efficacy and Safety of LASIK Combined with Accelerated Corneal Collagen Cross-Linking for Myopia: Six-Month Study.

This was a prospective controlled clinical trial. 48 myopia patients (96 eyes) were included in this study. After LASIK, accelerated corneal collagen cross-linking (ACXL) was used for myopia treatment. During 6-month follow-up, the results of LASIK-ACXL treatment were studied and compared to the LASIK-only procedure. The results showed that no statistically significant differences in UDVA, CDVA, MRSE, K mean, pachymetry, or ECD were found between the two groups at the visit after 6 months of follow-up (all P > 0.05). At 6 months postoperatively, 2 eyes lost one or more lines of visual acuity in the LASIK-ACXL group, whereas all LASIK-only treated eyes had a stable CDVA. In vivo confocal microscopy showed a decrease of keratocyte density and appearance of honeycomb-like structures in the anterior residual stroma bed; the changes were similar but more pronounced following LASIK-only. None of the cases in both groups developed signs of significant keratitis, regression, or ectasia during the 6-month follow-up. LASIK-ACXL can effectively correct refractive error in patients with myopia, with no significant complications during 6-month follow-up, indicating stability and morphologic change similar to those with LASIK-only treatment.

Comparison of the Early Clinical Outcomes between Combined Small-Incision Lenticule Extraction and Collagen Cross-Linking versus SMILE for Myopia.

Background. To compare the early outcome of combined SMILE and collagen crosslinking (SMILE Xtra) with SMILE. Method. Prospective, comparative interventional study of 21 eyes receiving SMILE Xtra using a low energy protocol and 32 control eyes receiving SMILE only. The outcomes were compared at 1, 3, and 6 months postoperatively. Results. Both groups had myopia with spherical equivalent refraction (SEQ) > 4.00 D. The SMILE Xtra group had thinner preoperative central corneal thickness and residual stromal bed thickness (p < 0.021). At 6 months, no eyes lost more than 1 line in corrected distance visual acuity. The safety index was 0.96 ± 0.06 and 1.00 ± 0.00 in SMILE Xtra and control, respectively (p < 0.001). 89% and 94% of eyes were within ±0.50 D of target refraction, respectively, with the mean error in SEQ correction being −0.17 ± 0.26 D for SMILE Xtra and +0.03 ± 0.25 D for control (p = 0.021). The efficacy index was 0.88 ± 0.13 and 0.97 ± 0.06, respectively (p = 0.005). Conclusion. SMILE Xtra had good overall safety profile and predictability at 6 months. However, when compared with control, the safety index and efficacy index were statistically significantly lower in the early postoperative period.

Options for a young patient with considerably high, topographically stable, astigmatism: December consultation #1

A 21-year-old woman was referred for a refractive surgery evaluation. She has no relevant allergies or medical or family history of keratoconus or corneal transplantation. Spectacle dependence is her chief complaint. She occasionally wears contact lenses but wants to have surgery performed. The corrected near visual acuity and the corrected distance visual acuity (CDVA) are 20/20 in both eyes. The manifest refraction is 5.75 3.25 178 in the right eye and 5.00 3.50 170 in the left eye. The intraocular pressure and the results from a slitlamp examination and a fundus retinoscopy are normal. The ultrasound pachymetry shows the central corneal thickness (CCT) to be 505 mm in the right eye and 508 mm in the left eye. Among all devices used tomeasure the CCT, the thinnest measured point is 504 mm in the right eye and 503 mm in the left eye. Placido-disk corneal topography shows a high regular symmetric astigmatism that was stable over 1 year of follow up, with an insignificant change in keratometry (K) values (Figure 1). The 5 topographies were obtained at 3-month intervals. Scheimpflug and dual Scheimpflug tomography (Figures 2, 3, and 4) are normal with no suspicious pattern except a high regular astigmatism. The pachymetry maps show corneas that, although slightly thin, are within normal limits across the diameter. An excimer laser system predicts a stromal ablation of approximately 127 mm in the right eye and 121 mm in the left eye. For laser in situ keratomileusis (LASIK) with a 110 mm flap thickness, the percentage of tissue altered (PTA) would be 47% in the right eye and 46% in the left eye. The residual stromal bed (RSB) would be 267 mm in the right eye and 272 mm in the left eye. For photorefractive keratectomy (PRK), the PTA would be 25% in the right eye and 24% in the left. What kind of refractive surgery (if any) would you recommend to this patient? If none, why? Would you consider LASIK with a thin, predictable LASIK flap? What data helped you most in making your decision? Did the stability shown by the Placido disk–based corneal topography over 1 year significantly affect your surgery decision?What are your limits for treating a cornea with high regular symmetric astigmatism? If you recommend proceeding with surgery, was age a significant factor in that decision?

Anterior Chamber Stabilization in Combined Penetrating Keratoplasty With Scleral-Sutured Posterior Chamber Intraocular Lens Implantation.

To describe a novel technique for a stabilized penetrating keratoplasty procedure with implantation of a scleral-sutured posterior chamber intraocular lens in which the anterior chamber (AC) is maintained and the globe stabilized without using a Flieringa ring. In this procedure, a deep anterior corneal lamella separation was created. Four small incisions were made in each quadrant along the outer edge of the trephination groove of the residual stromal bed (RSB). The first incision at the 9-o'clock position was advanced with scissors in both clockwise and counterclockwise directions. This procedure was repeated in the remaining 3 quadrants, creating 4 small bridges between the RSB and corneal rim. A donor corneal button coated with a viscoelastic material was sutured at 3 incision sites leaving 1 quadrant sutureless to allow sufficient incision width for IOL insertion for scleral fixation. Scleral fixation of a 1-piece polymethyl methacrylate (PMMA) IOL was performed. After sequential cutting of the bridges, the RSB was removed from the AC. Ten eyes of 10 patients underwent this procedure without significant complications. There were no complications related to the open-sky procedure. Globe stabilization was achieved in all surgeries. Endothelial cell loss, visual acuities, and graft failure rates were comparable with the reports of AC-protecting penetrating keratoplasty surgeries. This technique provides a secured AC and stabilized globe without the use of a Flieringa ring and increases the surgical safety without a significant reduction of the graft endothelial cell density.

Options for an eye with a thin cornea: June consultation #1

Journal of Cataract & Refractive Surgery: June 2015 - Volume 41 - Issue 6 - p 1324-1327 doi: 10.1016/j.jcrs.2015.06.006

Iatrogenic Keratectasia: A Review

Iatrogenic corneal ectasia is a rare complication but also one of the most feared situations that can occur after uneventful corneal laser surgery. Ectatic changes can occur as early as 1 week or can be delayed up to several years after LASIK. The actual incidence of ectasia is undetermined, an incidence rate of 0.04 to almost 2.8 % has been reported. Ectasia is most common following LASIK; however, cases have been reported following PRK and other corneal refractive procedures. Keratectasia shows progressive myopia, irregular astigmatism, ghosting, fluctuating vision and problems with scotopic vision. The progression leads to severe loss of corrected visual acuity. Risk factors are thin corneas < 500 µm, a pathological corneal topography, a residual stromal bed < 300 µm, high myopia > 8 D, young (female) age < 25 years, atopic dermatitis, allergies, family history for keratokonus and collagen diseases and retreatments. Treatment of choice is a cross-linking with riboflavin/UVA light with contact lenses. In severe cases a penetrating or a deep anterior lamellar graft is necessary.

Role of Percent Tissue Altered on Ectasia After LASIK in Eyes With Suspicious Topography

To investigate the association of the percent tissue altered (PTA) with the occurrence of ectasia after LASIK in eyes with suspicious preoperative corneal topography. This retrospective comparative case-control study compared associations of reported ectasia risk factors in 129 eyes, including 57 eyes with suspicious preoperative Placido-based corneal topography that developed ectasia after LASIK (suspect ectasia group), 32 eyes with suspicious topography that remained stable for at least 3 years after LASIK (suspect control group), and 30 eyes that developed ectasia with bilateral normal topography (normal topography ectasia group). Groups were subdivided based on topographic asymmetry into high- or low-suspect groups. The PTA, preoperative central corneal thickness (CCT), residual stromal bed (RSB), and age (years) were evaluated in univariate and multivariate analyses. Average PTA values for normal topography ectasia (45), low-suspect ectasia (39), high-suspect ectasia (36), low-suspect control (32), and high-suspect control (29) were significantly different from one another in all comparisons (P < .003) except high- and low-suspect ectasia groups (P = .033), and presented the highest discriminative capability of all variables evaluated. Age was only significantly different between the high-suspect ectasia and normal topography ectasia groups, and CCT was not significantly different between any groups. Stepwise logistic regression revealed the PTA as the most significant independent variable (P < .0001), with RSB the next most significant parameter. There remains a significant correlation between PTA values and ectasia risk after LASIK, even in eyes with suspicious corneal topography. Less tissue alteration, or a lower PTA value, was necessary to induce ectasia in eyes with more remarkable signs of topographic abnormality, and PTA provided better discriminative capabilities than RSB for all study populations.

Changing a paradigm : PTA is more important than the residual stromal bed as a risk factor for post -LASIK ectasia

Changing a paradigm : PTA is more important than the residual stromal bed as a risk factor for post -LASIK ectasia

Corneal transplantation in keratoconus: Penetrating keratoplasty versus deep anterior lamellar keratoplasty with Melles technique

ObjectivesTo evaluate the effectiveness of deep anterior lamellar keratoplasty (DALK) using Melles technique (technique B) in patients with advanced keratoconus versus a classic technique, penetrating keratoplasty (technique A). MethodologyRetrospective descriptive comparative study between technique A and technique B in homogeneous groups. ResultsBest corrected visual acuity (Snellen test decimal scale) was 0.77±0.32 for group A and 0.62±0.29 for group B, with no statistically significant differences. The mean spherical final refraction in group A was 1.73±5.1 diopters, and the mean spherical equivalent was −3.92±5.1. Technique B group gave values −2.67±4.02 diopters and −4.55±4.08 diopters, respectively, with no statistically significant differences. The residual cylinder after removal of the sutures was 4.47±2.47 diopters for group A and 3.77±1.63 for group B, with no statistically significant differences. ConclusionNo statistically significant differences were found for any of the studied variables when comparing both groups using the t-test for independent samples. More studies on the homogeneity and residual stromal bed thickness could provide the key to determine whether this technique is closer to the visual acuity of penetrating keratoplasty or DALK by a descemet technique.

Refractive outcome of wavefront guided laser in situ keratomileusis and wavefront guided photorefractive keratectomy in high pre-existing higher order aberration.

To compare visual outcome and higher order aberrations (HOA) between wavefront-guided LASIK (WF-LASIK) and wavefront guided PRK (WF-PRK) in patients with high preoperative HOA. Randomized prospective interventional study. Conducted at Guru Nanak Eye Centre, Maulana Azad Medical College, Delhi, India. Eighty myopic eyes of forty patients were included. age more than 21 years, best corrected visual acuity of 20/20 or better, a stable refraction, to be off soft contact lens for minimum 14 days prior to preoperative examination, preoperative RMS HOA more than 0.35 μ, preoperative central corneal thickness at least 500 μm, estimated residual stromal bed thickness of at least 275 μm in patients undergoing WF-LASIK and 350 μm in patients undergoing WF-PRK. Exclusion criteria were severe dry eye, blepharitis, corneal disease and warpage, uveitis, posterior segment abnormalities involving the macula or optic nerve and systemic diseases. Patients were randomly divided into two groups. They underwent either WF-LASIK (group A) or WF-PRK (group B) over 2 years (40 eyes each). Patients were followed up for 6 months. Main outcome measures were efficacy, safety, stability, predictability and HOA. At 6 months mean uncorrected visual acuity (logMAR) in group A was -0.01 ± 0.04 and group B was 0.00 ± 0.07 (P = 0.23). HOA RMS (6mm pupil) in group A was 0.61 ± 0.24 μm and group B was 0.55 ± 0.25 μm. The increase was statistically significant in both the groups (P < 0.05). Both the groups showed similar efficacy, predictability and safety. WF-LASIK and WF-PRK have similar efficacy, safety and predictability, though WF-PRK induces less HOA.