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PURPOSE To assess satisfaction, quality of life, occupational impact, and clinical outcomes of physicians who have undergone laser vision correction (LVC) using either wavefront-optimized (WFO) or topography-guided (TG) excimer laser ablation profile with femtosecond laser flap creation. SETTING Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. DESIGN Retrospective survey study. METHODS A 12-question survey was sent to all physicians who underwent laser in situ keratomileusis or photorefractive keratectomy at the Cole Eye Institute between 2011 and 2018 on the WaveLight Allegretto Wave Eye-Q Laser (Alcon Laboratories, Inc.). Visual outcomes were obtained from patient charts. RESULTS Two hundred thirty-five physicians (454 eyes) met the study's inclusion criteria, including 181 physicians (353 eyes) who underwent WFO LVC and 54 physicians (101 eyes) who underwent TG LVC. One hundred seventeen physicians (49.8%) responded to the survey and reported an overall satisfaction rate of 98.3% among all physicians receiving LVC with 96.6% reporting they would have the procedure again. Visual outcomes showed a high level of surgical predictability, efficacy, and safety among WFO and TG eyes, with a higher percentage of eyes that received TG ablation achieving 20/10 vision (22% vs 4%, P < .0001) and 20/15 vision (87% vs 69%, P < .01) when compared with WFO eyes. CONCLUSIONS Physicians who had undergone LVC with either WFO or TG excimer laser ablation reported high satisfaction and quality-of-life improvements. Both groups achieved excellent visual outcomes, with a higher percentage of TG eyes achieving 20/10 and 20/15 vision.

Purpose To identify the laser programming strategy that will achieve optimal refractive outcomes of LASIK with a topography-guided laser for eyes with a disparity between cylinder measured by manifest refraction and cylinder measured by topography. Setting Six surgeons at 5 clinical sites in the USA. Design Retrospective data review. Methods Preoperative, treatment, and postoperative data on 52 eyes that underwent topography-guided LASIK with the WaveLight EX500 Contoura® Vision excimer laser ablation profile in which the vectors representing the preoperative refractive cylinder and the cylinder measured by the WaveLight® Topolyzer™ VARIO Diagnostic Device (Vario cylinder) differed by >/= 0.50D and/or >/= 10 degrees of orientation were analyzed retrospectively. Data were contributed by six surgeons using the laser at 5 different clinical sites. Vector analysis of postoperative cylindrical refractive error and the actual laser programming strategy was used to calculate the cylindrical correction that would, theoretically, have completely eliminated postoperative refractive cylinder. This was compared to expected results using the preoperative manifest cylinder, the topographic cylinder, and the Phorcides Analytic Engine (Phorcides LLC, North Oaks MN; Phorcides). For analysis, subjects were stratified on the basis of the vector difference between Manifest and Topo cylinder (High, >0.75 D; and Low, ≤0.75 D). Results The poorest calculated theoretical outcomes were obtained with the manifest refraction (centroid: -0.43, 0.22; mean calculated error vector: 0.56 ± 0.42 D; p=ns). Better outcomes were obtained with the topographically measured refraction (centroid: 0.37, 0.02; mean calculated error vector: 0.47 ± 0.33 D; p=ns). The best outcomes were obtained with Phorcides (centroid: -0.15, 0.06; mean calculated error vector: 0.39 ± 0.28 D; p=ns). The mean error vector magnitude in the Phorcides Low group was significantly lower than for the Manifest and Topo Low groups (0.26 D vs 0.48 D and 0.33 D; p

Purpose To analyze planning strategies for eyes that gained 1 or more lines of corrected distance visual acuity (CDVA) after topography-guided custom treatment (TCAT). Setting Refractive Surgery Clinic, Cleveland Clinic, Ohio, USA. Design Retrospective case series. Methods Eyes having TCAT by the same surgeon between February 2016 and June 2017 were enrolled. The corneal shape was captured with the Wavelight Allegretto Topolyzer diagnostic device coupled with refraction, generating an ablation profile. The cylinder magnitude and axis of laser entry were decided by the surgeon based on the manifest and measured values, assisted by additional data from the Pentacam Scheimpflug tomographer and Ladarwave ocular wavefront aberrometer. Results The study comprised 256 eyes. At 3 months, uncorrected distance visual acuity was 20/20 or better in 95.7% and 20/15 or better in 81.4%; 25.6% gained 1 or more lines of CDVA. The measured and manifest axes differed by less than 15 degrees in 59%, between 15 degrees and 30 degrees in 18%, and by more than 30 degrees in 23%. When it differed by at least 5 degrees, the measured axis was treated in 79%, 75%, and 73% of eyes, respectively. In eyes with higher measured cylinder, 75% were treated between the manifest and measured values, with 7% at full measured value. When the manifest value was greater, 60% were treated at the total measured value and 40% in between. Whole-eye aberrometry showed a small increase in coma, spherical aberration and the total root mean square (all P Conclusions The TCAT procedure achieved visual acuity better than the preoperative CDVA in more than 25.0% of eyes. Tomography and wavefront aberrometry assisted in the selection process to achieve optimum visual outcomes.

As a flapless procedure, SMILE brings benefits to refractive surgery, such as lower corneal biomechanical impact, less dry eye risk and less stromal bed exposure. However, the longer learning curve can be a risk factor for complications. This article aims to discuss SMILE complications and proposes a categorized analysis of occurrences, dividing into two groups: intraoperative and postoperative complications. Among intraoperative, we also suggest a subdivision between those related to the laser (lenticule construction), tissue separation (lenticule dissection) and tissue removal (lenticule extraction).The majority of SMILE complications are related to surgeon inexperience and reversible if precociously diagnosed and correctly managed. Intraoperative complications related to lenticule creation such as suction loss, opaque bubble layer and black spots, are correlated with later difficulties during lenticule dissection and removal, and may lead to unwanted situations, such as cap perforation, lenticule tear and cap-lenticule adhesion. Postoperative complications as dry eye, keratitis and ectasia should not be underestimated.Analyzing what has been reported as major or unique among the complications with SMILE, and dividing them into subgroups, we aim to help refractive surgeons in becoming familiar with the things that can go wrong during SMILE. Early recognition and correct management will be fundamental for optimizing the final visual result.

PURPOSE The objective of this study was to review the advances in the field of refractive surgery as reported in the peer-reviewed literature during the previous year. DESIGN A literature review. METHODS In this review, we highlight the most pertinent articles in the field from June 2014 to the end of July 2015. RESULTS This past year has seen a growing body of research on small-incision lenticule extraction, presbyopic inlays, and phakic intraocular lenses, as more clinicians are adopting these techniques into their armamentarium. CONCLUSIONS Laser-assisted in situ keratomileusis and photorefractive keratectomy continue to dominate the keratorefractive literature, as they remain the most frequently performed refractive surgeries.

PURPOSE: To evaluate extracellular matrix regulators and inflammatory factors in a patient who developed ectasia after small incision lenticule extraction (SMILE) despite normal preoperative tomographic and biomechanical evaluation. METHODS: The SMILE lenticules from both eyes of the patient with ectasia and three control patients (5 eyes) matched for age, sex, and duration of follow-up were used for gene expression analysis of lysyl oxidase (LOX), matrix metalloproteinase 9 (MMP9), collagen types I alpha 1 (COLIA1) and IV alpha 1 chain (COLIVA1), transforming growth factor-beta (TGF-beta), bone morphogenetic protein 7 (BMP7), interleukin-6 (IL-6), cathepsin K, cluster of differentiation 68, integrin beta-1, and tissue inhibitor of metalloproteinase-1 (TIMP1). Furthermore, the functional role of LOX was assessed in vitro by studying the collagen gel contraction efficiency of LOX overexpressing in primary human corneal fibroblast cells. RESULTS: Preoperatively, manifest refraction was −9.25 diopters (D) in the right eye and −10.00 D in the left eye. Corneal thickness, Pentacam (OCULUS Optikgeräte GmbH, Wetzlar, Germany) tomography, and Corvis biomechanical indices (OCULUS Optikgeräte GmbH) were normal. The ectatic eye lenticule (left) had reduced expression of LOX and COLIA1 compared to controls without ectasia. Increased mRNA fold change expression of TGF-beta, BMP7, IL-6, cathepsin K, and integrin beta-1 was noted in the ectatic left eye compared to controls; however, MMP9 and TIMP1 levels were not altered. Ectopic LOX expression in human corneal fibroblast induced significantly more collagen gel contraction, confirming the role of LOX in strengthening the corneal stroma. CONCLUSIONS: Reduced preexisting LOX and collagen levels may predispose clinically healthy eyes undergoing refractive surgery to ectasia, presumably by corneal stromal weakening via inadequately cross-linked collagen. Preoperative molecular testing may reveal ectasia susceptibility in the absence of tomographic or biomechanical risk factors. [ J Refract Surg . 2019;35(1):6–14.]

PURPOSE: To investigate the association of the percent tissue altered (PTA) with the occurrence of ectasia after LASIK in eyes with suspicious preoperative corneal topography. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. [ J Refract Surg. 2015:31(4):258–265.]

To compare objective and subjective metrics from regular and high-resolution Scheimpflug devices (Pentacam) to determine their equivalence and interchangeability for refractive surgery screening.Emory Vision at Emory University, Atlanta, Georgia, USA.Retrospective comparative case series.Eyes of consecutive screened refractive surgery patients were evaluated with high-resolution and regular Scheimpflug devices. Objective parameters evaluated included keratometry (K) values, central corneal thickness (CCT), and device-generated keratoconus screening indices. Masked expert reviewers subjectively graded images as normal, suspicious, or abnormal.One hundred eyes of 50 patients were evaluated. The mean K values were not significantly different (anterior K: high resolution 1.21 diopters [D] ± 1.13 (SD) versus regular 1.15 ± 1.16 D, P = 0.73; posterior K: 0.34 ± 0.23 D versus regular 0.35 ± 0.23 D, P = .67). The mean CCT was significantly thinner in the high-resolution group (514.7 ± 26.6 μm versus 527.6 ± 27.6 μm (P.0001) with limits of agreement of -12.9 to +17.5 μm. Most keratoconus screening indices were more suspicious with the high-resolution device than with the regular device except the indices of height asymmetry and height deviation. Subjectively, 60% of cases received the same score, high resolution was more suspicious in 28% of cases, and regular was more suspicious in 12% of cases; there was only slight subjective agreement between technologies (κ = 0.26 to 0.31).Regular and high-resolution Scheimpflug imaging devices generated different objective values and significantly different subjective interpretations with poor inter-reviewer agreement. The high-resolution device provided a more conservative overall output. For refractive surgical screening, the 2 devices are not interchangeable.Proprietary or commercial disclosures are listed after the references.

Purpose To document the first presented report in December 2008 of high irradiance riboflavin/ultraviolet A (UVA) corneal cross-linking in comparison with that of standard irradiance and of fractionated exposure to increase the time for oxygen diffusion into the cornea. Methods After in vitro studies of oxygen depletion and cross-linking density using type 1 human collagen gels, 36 ex vivo porcine globes were deepithelialized and exposed to 0.1% riboflavin drops in carboxymethylcellulose solution every 5 min for 3 initial doses and then throughout irradiation afterward. Six eyes each were irradiated with 370-nm UVA light at 2, 3, 9, and 15 mW/cm continuously and 15 mW/cm fractionated (with alternate cycles of 30 s "ON" and 30 s "OFF" exposure) using an equivalent radiant exposure of 5.4 mJ/cm. The final six eyes received no UVA exposure as a control. The exposed corneas were then dissected and subjected to extensiometry. Analysis of variance with Bonferroni post hoc test was performed between groups. Results The stress required to induce a 10% strain for the control eyes (no UVA) was 100.6±20.9×10 N/m in comparison with the stress of 3 mW/cm (standard irradiation) at 146.7±17.6×10 N/m (P=0.009). The stress at the other equidose irradiances of 2, 9, 15 continuously, and 15 mW/cm fractionated were 140±21.9, 162.8±70, 154.1±70, and 163.0±64×10 N/m, respectively. When comparing the irradiances of 15 mW/cm continuously and fractionated to the standard irradiation, the stress was not statistically different (P=0.799 and 0.643), respectively. Conclusion High irradiance riboflavin/UVA cross-linking with equivalent energy exposure demonstrates comparable efficacy in stiffening corneal collagen with standard irradiance, but with considerably less exposure time. Over the past 6 years, since this report was first presented, the use of high irradiance cross-linking has been gaining popularity.

Purpose To evaluate the satisfaction and quality of life after laser vision correction (LVC) exclusively in a physician population. Setting Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. Design Cohort study. Methods A 12-question survey targeted toward physicians and the unique qualities of their experience with refractive surgery was sent to physicians who had refractive surgery at the Cole Eye Institute between 2000 and 2012. In conjunction, the visual outcomes and clinical information of physicians who received the survey were reviewed. Results Two hundred twenty-six physicians (439 eyes) met the inclusion criteria for our study. One hundred thirty-two physicians (58%) responded to the survey and reported an overall satisfaction rate of 95.3%. Respondents included surgeons (28.0%), physicians who perform procedures but not surgery (43.2%), and physicians who do not perform procedures or surgery (28.8%). Of the physicians, 84.8% reported an improvement in the quality of vision compared with the corrected preoperative vision, 39.0% reported that their ability to perform procedures accurately had improved and 1.6% said they believed their ability to perform procedures was less. Ninety-six percent reported they would have the procedure again. Visual outcomes showed high levels of surgical predictability, efficacy, and safety. Conclusion Despite high visual demands, physicians having LVC had a high percentage of good visual outcomes, satisfaction, and quality-of-life improvements. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Myopia is a generally benign refractive error with an increasing prevalence worldwide. It can be corrected temporarily with glasses and contact lenses and permanently with laser vision correction. The 2 main procedures currently being performed for myopia correction are photorefractive keratectomy and laser-assisted in situ keratomileusis. Each technique has its advantages, but they appear to yield similar visual outcomes 1 year after surgery. Laser vision correction for myopia was considered a paradigm shift because healthy eyes could now undergo a surgical procedure to permanently and safely correct the error by altering the center of the cornea, which was previously off limits because of the potential for loss of transparency. Customized ablation using wavefront aberrometry and its optimized profiles were created to correct higher-order aberrations and give more vision quality to patients. Topography-guided ablation, initially used for complex retreatments, shows potential to make vision even better than glasses and contact lenses in a recent study on previously untreated eyes. One major concern is to identify corneas that are at risk of developing ectasia after the procedure. Topographic and tomographic screening indices have been implemented clinically, but there is still much to learn about corneal biomechanics. A more recently developed procedure for myopia correction is small-incision lenticule extraction, in which a lenticule is created in the cornea's stroma with a femtosecond laser and extracted through a small corneal incision. Long-term outcomes and new complication risks need to be better understood as this procedure develops.

PURPOSE: To report a new indication for flap lift of interface blood using the WaveLight FS200 femtosecond laser (Alcon Laboratories, Inc., Fort Worth, TX). METHODS: The unique evacuation canal of the FS200 femtosecond laser allows blood from injured limbal vasculature to accumulate. In rare instances, blood extends from the canal into the flap interface, requiring a flap lift. All flap lifts were performed using the microscope in the laser suite on the FS200 femtosecond laser to remove postoperative flap interface blood in 3 eyes of 3 patients. RESULTS: All interface blood was removed and no patients experienced re-bleeding. Postoperatively, patients achieved an uncorrected visual acuity of 20/20. CONCLUSIONS: When intracanal blood is noted, planned incomplete dissection of the flap to the canal edge may prevent the progression of blood in the interface. [ J Refract Surg . 2014;30(12):858–860.]

To investigate the association between femtosecond laser flap parameters, uncorrected distance visual acuity, and higher-order aberrations (HOA) after customized myopic LASIK. Retrospective review of the charts of patients who underwent uncomplicated wavefront-guided customized myopic LASIK with flap creation using the femtosecond laser. Patients were stratified by intended flap thickness, and the change in HOA from preoperative to 3 months postoperative was compared. Multivariate linear models were performed to assess the association between calculated flap thickness, intended flap diameter, HOA, and uncorrected visual acuity. One hundred seventy-one eyes of 171 patients were included. There was no statistically significant difference in the induction of HOA between eyes with thin (90 μm) or thick (100 or 110 μm) intended flaps. In a multivariate model, the level of myopic correction was highly associated with the induction of total HOA, coma, and spherical aberration. There was no correlation between calculated flap thickness, uncorrected visual acuity, or HOAs. Intended flap diameter was not associated with coma or spherical aberration, but larger flap diameter was associated with better uncorrected visual acuity. Femtosecond laser flap thickness in the range of 90–110 μm was not associated with uncorrected visual acuity or the induction of HOA after uncomplicated customized myopic LASIK. The level of myopic correction was the largest determinant of the induction of HOA.

This review of wavefront technology looks at 2 major aspects. The first is the basics and principles of the optics of the eye, how to decompose the wavefront in a more adequate way for interpretation, and how these aberrations affect the visual acuity. It also addresses the diversity and complexity of wavefront sensors; how these devices transform the principles into clinically useful data, with the advantages and limitations of each system. The second major aspect is the clinical uses of the technology: wavefront-guided and newer and enhanced profiles related to wavefront as well as the limitations of the technology. Finally, recent innovations made possible by wavefront technology that are not limited to refractive surgery are reviewed.

PURPOSE: To provide an overview of the clinical results of different ablation profiles based on wavefront technology and discuss their characteristics and limitations. METHODS: Literature review of studies reporting results of ablation profiles based on wavefront technology in virgin healthy eyes. RESULTS: Over the past 10 years, a large number of studies comparing different treatment algorithms and newer excimer laser platforms have been published. Thirty-six clinical studies including 3637 eyes analyzing the clinical results obtained after wavefront-guided, wavefront-optimized, and Q-factor profiles have been reviewed. Although wavefront-driven profiles allowed reduction of the amount of induced optical aberrations with conventional ablations, thereby improving the quality of vision, it appears that no algorithm of treatment or excimer laser platform has demonstrated a clear superiority over another. Wound healing and unexpected biomechanical response to surgery affect the accuracy of customized treatments and produce variable results. In addition, it is difficult to rigorously analyze and compare findings among different studies because of the diverse variety in which the data are reported. CONCLUSIONS: Despite several technological improvements over the years, wavefront ablation profiles have not consistently demonstrated superiority in terms of visual acuity and lower order aberrations compared to the standard procedure, although the induction of higher order aberrations has been reduced. The concept of an individualized eye model has emerged recently, based on the optical ray tracing algorithm, and could theoretically provide a higher level of customization, thus fulfilling the promise of “super vision.”

Refractive surgery is a procedure that requires excellence. Nothing less than the best is acceptable for an elective procedure that must be precise, accurate and safe. Femtosecond lasers were developed to help fulfill these requirements and have changed the field. The capabilities of the technology include not only the creation of corneal flaps for laser-assisted in situ keratomileusis, but limitless corneal- and lens-based incisions, as well as glaucoma and retinal applications that can break old paradigms. Manipulating biomechanics to correct presbyopia with the IntraCor procedure, the ‘femtosecond-only’ femtosecond lenticule extraction or SmILE procedures, intrastromal astigmatic incisions and cataract surgery are among the next exciting applications to this technology. New fields in refractive surgery can be opened and others can be expanded, as in refractive lens exchange, where its indications may be greatly increased, considering the new safety and precision standards that the technology can delive...

doi:10.3928/1081597X-20090917-04 T he fi rst thing that the reader might question in viewing this editorial is “What does he mean by biomechanical manipulation?” It is true that corneal biomechanics has been a relatively new, hot topic in refractive surgery, but why manipulation? To answer this question, let me go back to the beginning of refractive surgery to outline a trend in the way our fi eld has evolved.

To compare central (CCT) and peripheral corneal thickness (PCT) using Scheimpflug imaging (Pentacam), high-speed optical coherence tomography (Visante OCT), and ultrasound (US) pachymetry (Sonogage Corneo-Gage Plus) in normal, keratoconus-suspect, and post-laser in situ keratomileusis (LASIK) eyes.Department of Refractive Surgery, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA.The CCT and PCT were retrospectively measured using US pachymetry, Scheimpflug imaging, and high-speed OCT from January 2006 to March 2008. The influence of age and absolute magnitude of corneal thickness were also analyzed. Analysis was by multivariate generalized estimating equations, multivariate linear regression, and linear regression plots.One hundred sixty-three eyes were analyzed. Ultrasound pachymetry CCT measurements were consistently higher than Scheimpflug and OCT measurements (mean difference 6.5 microm +/- 1.8 [SD] and 7.5 +/- 1.4 microm, respectively) (both P.0005) in normal eyes; the difference was statistically similar and not greater with keratoconus suspicion, age, or absolute magnitude of corneal thickness (P.05). Scheimpflug measurements were significantly lower than US pachymetry in post-LASIK eyes (P.0005). There was no statistically significant difference (mean 0.9 +/- 1.4 microm) in Scheimpflug and OCT CCT measurements (P.5), although Scheimpflug measurements were significantly lower in post-LASIK eyes (P.0005). Scheimpflug PCT measurements were higher than OCT measurements, showing more agreement with increasing age (P = .017).Scheimpflug and OCT CCT measurements were reproducible but always thinner than US pachymetry in normal and keratoconus-suspect eyes. In post-LASIK eyes, OCT pachymetry maps were more accurate than Scheimpflug maps. The influence of age on PCT requires further study.

PURPOSETo describe a series of myopic patients in whom a LASIK flap was created with the IntraLase femtosecond laser. The LADARVision (Alcon Laboratories Inc) tracking system failed and resulted in postponement of surgery. METHODSFive myopic Asian patients with darkly pigmented irides underwent bilateral superior hinge flap creation with three different femtosecond laser (IntraLase Corp) pulse frequencies: 15, 30, and 60 kHz. Mean patient age, preoperative best spectacle-corrected visual acuity (BSCVA), and spherical equivalent refraction were 33 years, 20/20, and –6.25 diopters (D), respectively. Despite uncomplicated flap-lift and adequate pharmacologic dilated pupil diameter >7 mm, difficulty was experienced with LADARVision eye tracking in 9 of 10 eyes. Intraoperative manipulations (fluid application, levitation of the laser bed, and tracking through a repositioned flap) were attempted to facilitate eye tracking at the time of femtosecond laser flap creation, but without success. RESULTSThe flap was repositioned, and patients were asked to return 1 to 5 days later, at which time the flap was relifted, eye tracking was successfully achieved, and the surgery was completed. Mean postoperative uncorrected visual acuity was 20/18 and no eyes lost any lines of BSCVA at 1 year. CONCLUSIONSIrregularities of the IntraLASIK stromal bed surface induce forward light scatter, and dark ocular pigmentation further reduces retinal reflectance, leading to tracking failure with the Alcon LADARVision platform. Delaying the surgery by 1 to 5 days may aid in reducing the light scatter, so that eye tracking can be achieved. [J Refract Surg. 2008;24:953-956.] AUTHORS From the Department of Refractive Surgery, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio. Dr Krueger receives travel support and research funds from Alcon Laboratories Inc, Ft Worth, Tex. The remaining authors have no financial or commercial interest in the materials presented herein. Correspondence: Ronald R. Krueger, MD, MSE, Cole Eye Institute, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195. Tel: 216.444.8158; Fax: 216.445.8475; E-mail: krueger@ccf.org Received: December 22, 2007 Accepted: May 14, 2008 Posted online: July 31, 2008

PURPOSE: To examine flap morphology, corneal topography, and aberrometry after flap creation with a femtosecond laser in one eye and a mechanical microkeratome in the fellow eye. Comparative outcomes after subsequent refractive laser correction were also investigated. METHODS: Two patients (4 eyes) were enrolled in a clinical study in which LASIK flaps were created using the IntraLase laser set at 90 or 100 µm in one eye and the Moria M2 microkeratome with a 90-µm head in the fellow eye. Pre- and postoperative flap data at 1 day, 1 week, and 1 month were collected before lifting the flap to perform a customized laser ablation (Alcon LADARVision4000 CustomCornea System). Postoperative laser data were collected at 1 week, 1 month, 3 and 6 months, and 1 year. Visual acuity, pachymetry, high-frequency flap ultrasound profilometry (Artemis Ultralink), topography, aberrometry (LADARWave), and refraction were examined and compared between eyes. RESULTS: Postoperative flap comparisons showed a hyperopic refractive shift in all four eyes with a shift of up to 1.00 diopter (D) in the microkeratome eyes and CONCLUSIONS: Femtosecond laser and mechanical methods of flap creation lead to subtle biomechanically induced aberrations, which appear more prominent with the mechanical Moria M2 microkeratome in this small case study. Further study with a larger patient population is warranted to determine whether these differences are statistically significant. [J Refract Surg. 2007;23:800-807.]

PURPOSE: To determine how changes in corneal elasticity/stiffness might influence intraocular pressure (IOP) readings in diabetic patients. METHODS: A systematic review of the literature was performed to understand the conflicting relationship between diabetes, elevated IOP, and glaucoma progression. RESULTS: Diabetic patients have been found to have statistically significant higher IOP readings in some population-based studies compared to non-diabetics. Insulin resistance states, hyperglycemia and glycosylated hemoglobin have been correlated with higher IOP (1 mmHg) measurements in diabetic patients. In the Ocular Hypertension Treatment Study (OHTS), a self reported history of diabetes was found to be protective against the progression of primary open-angle glaucoma. Small differences in IOP measurements in diabetic patients may be due to corneal stiffening, as demonstrated by the protective effect of glucose-mediated collagen cross-linking against the manifestation and keratometric progression of keratoconus. Different collagen cross-linking agents may induce different degrees of corneal stiffening, which can result in differences in measured IOP. CONCLUSIONS: Glucose-mediated corneal stiffening due to collagen cross-linking might be responsible for IOP overestimation in diabetic patients. Corneal stiffening might explain why diabetic eyes tend to have higher IOP readings in large population-based studies and why those with ocular hypertension have a reduced risk for glaucoma progression. [J Refract Surg. 2007;23:85-88.]

Purpose The field of refractive surgery is changing quickly in the areas of screening, treatment, and postoperative management. The objective of this study was to review advances in the field of refractive surgery as reported in the peer-reviewed literature during the previous year. Design This was a literature review. Methods In this article, we highlight the progression in the field from May 2013 to the end of June 2014. This article is organized as preoperative, intraoperative, and postoperative considerations. Results The growing use of newer modalities of treatment, such as small-incision lenticule extraction (SmILE) and phakic intraocular lenses, and their safety and efficacy add to the armamentarium in treating refractive error. This past year has seen many studies, which show these procedures to be safe and effective. Also, structurally, SmILE may result in a more biomechanically stable cornea, so that we may be able to safely treat higher refractive errors. Conclusions While laser-assisted in situ keratomileusis is the predominant surgical procedure, photorefractive keratectomy is still an appropriate choice in certain scenarios (higher risk for ectasia postrefractive surgery and patient choice) with safe, predictable results, and patient satisfaction. Many of the new developments in laser-assisted in situ keratomileusis have focused on flap creation with femtosecond lasers. Histopathology and in vivo optical coherence tomography studies have shown that the stromal bed is smoother, the side cuts are vertical, and the flap has predictable thickness. New surgical modalities, such as femtosecond lenticule extraction and SmILE, are increasingly being used.

Corneal cross-linking, a technique employing UV-A illumination and a photomediator to induce corneal rigidity, is a widely recognized procedure for the stabilization or even possibly reversal of corneal ectasia progression in patients with keratoconus and post-LASIK ectasia. A rapidly growing number of clinical reports suggest a consistent stabilizing effect of cross-linking along with a variable improvement in corneal shape and visual function in some patients. In the past ten years there has been a continuous effort into understanding, ensuring safety and efficacy, and further expanding its applications, as well as exploring modifications aiming to optimize the technique. Research in the field of CXL is highly dynamic; techniques, concepts, and indications are constantly evolving. Recent advances in corneal cross-linking include applications for infections treatment that do not respond to topical medications; accelerated, high-fluence applications; prophylactic application in refractive surgery; modified beam profiles for selective treatments; fully customized induction of refractive changes in nonectatic eyes. We welcome in this special issue several papers on this subject covering topics such as the issue of epithelial removal with hypotonic riboflavin solution, as well as a contralateral study on this subject; study investigating rate of corneal collagen cross-linking redo, investigating risk factors and safety, including a study investigating the profile of microbial keratitis following CXL; long-term investigation of safety and visual outcome of Visian toric ICL implantation after CXL in keratoconus; long-term investigation of accelerated CXL in paediatric patients; biomechanical effects investigation of the correlation between tomographic and biomechanical severity of keratoconic corneas; and a novel application of intraoperative optical coherence tomography in CXL. Keratoconus is considered an unpredictably progressive eye disease that “softens” the cornea. The progressive thinning and “bulging” of the cornea may distort or even significantly reduce vision. In advanced cases, one or more corneal transplant procedures and possibly additional eye surgeries may be required for visual rehabilitation. As it mainly affects younger people, it has severe consequences in their quality of life and their ability to contribute to the active workforce during their most productive years. In our experience within our ophthalmology center in Greece, through extensive studies conducted the last 10 years, we have found that in unpublished data possibly more than 1 out of 35 patients display some form of keratoconus in modern cornea diagnostics, compared to 1 out of 1,000–2,000 reported in Northern Europe and the United States. In addition, we have noted a higher degree of familial correlation of keratoconus reaching 90% topographic or tomographic suspicion in one of the two parents of a known young adult with keratoconus, a marked difference compared to the 10% genetic correlation that has been previously reported. Over the last decade a new treatment, collagen cross-linking (CXL), has been introduced. In this treatment, vitamin B2 and ultraviolet light (UV-A) are applied to the cornea in a short procedure that “stiffens” the cornea and stops disease progression.

Three patients (5 eyes) presented with complaints of monocular diplopia and no history of ocular trauma or surgery. The patients had comprehensive neuroophthalmic evaluation including manifest refraction, anterior segment and dilated fundus examination, and corneal topography. All patients also had wavefront analysis using the LADARWave system (Alcon). Two patients (4 eyes) also had hard contact lens overrefraction. The patients had a normal initial examination including corneal topography. One patient (2 eyes) did not experience resolution of diplopia with pinhole. No eye improved with manifest refraction or hard contact lens overrefraction. However, each patient had a significant amount of coma on wavefront analysis. Moreover, eyes with horizontal diplopia had horizontal coma and eyes with vertical diplopia had vertical coma as measured with the wavefront device. Higher-order optical aberrations such as coma may be associated with monocular diplopia. Wavefront technology may be useful in the workup of monocular diplopia.

Infectious keratitis is rare following laser vision correction. We present a case of aggressive fungal keratitis caused by Aspergillus flavus, following laser in situ keratomileusis (LASIK) in the setting of a unique environmental risk factor. We describe the key features of the acute case presentation, which guided empirical medical and surgical treatment, resulting in the most favorable outcome found in the literature, to date.

PURPOSE: To identify aberrations created by making a laser in situ keratomileusis (LASIK) flap and treating the refractive error with laser ablation at a later date. METHODS: Twenty-two eyes (11 patients) underwent a two-step LASIK procedure with the Alcon LADARVision laser (Alcon Laboratories, Ft Worth, Tex). In the first step, a flap was created, and 1 month later the flap was lifted and laser ablation performed. Aberrations were measured with the LADARWave wavefront measurement device preoperatively, after making the flap (1 day, 1 week, 1 month) and after laser treatment (1 week and 3 months). Two different microkeratomes were used (Moria M2 [Moria; Antony, France] and SKBM [Alcon]). With the SKBM, all flap hinges were nasal; with the Moria M2, the flap hinge was randomly selected as superior in one eye and nasal in the other. RESULTS: A slight hyperopic shift was seen in the manifest and wavefront refractions at 1 week and 1 month after flap creation for the Moria M2, but not for the SKBM. Statistically significant change in manifest sphere with the Moria M2 showed a mean shift at 1 month of +0.50±0.08 diopters (D) whereas the SKBM showed no mean shift, but less reproducibility, +0.06±0.17 D. Higher order aberrations after flap creation were statistically significantly higher for all except coma with both microkeratomes, but with no predictable trends observed. Although higher in magnitude, post flap aberrations were less than one quarter the increase noted in post laser aberrations, except for "other terms." CONCLUSIONS: Creating a LASIK flap induces changes in lower and higher order ocular aberrations. The change in lower order terms is microkeratome dependent. Higher order aberrations increase to a much larger degree after laser than after flap, making a two-step procedure unnecessary in conventional LASIK. [J Refract Surg. 2005;21:346-352.]

The corneal wound healing response following refractive procedures represents a subject of high relevance, due to its direct influence on the postoperative results. Technical modifications of current refractive procedures, like the automated flap creation with the femtosecond laser, LASEK, PRK with mitomycin C and Epi-LASIK have been proposed as alternatives to traditional LASIK and PRK. Several theoretical advantages have encouraged the diffusion of these new techniques; however, a better understanding of the corneal wound healing response following these procedures is required. The present text proposes a review of the corneal wound healing characteristics following different modalities of refractive surgical procedures.

PURPOSE: To describe the optical implications of the aberration pattern of a keratoconic eye implanted with an intrastromal corneal ring (Ferrara ring). METHODS: A 32-year-old man with bilateral keratoconus had a Ferrara intrastromal corneal ring implanted in his right eye. Surgery was uneventful and both uncorrected (UCVA) and best spectacle-corrected (BSCVA) visual acuity improved. Corneal topography was performed before and after surgery. Wavefront measurements were performed 1 month after the procedure in both eyes for comparison. The point spread function, modulation transfer function (MTF), and convolved acuity chart were analyzed. RESULTS: The right eye-implanted with the intrastromal Ferrara ring-had high root-mean-square (RMS) values for higher order aberrations. The left eye-keratoconus without an intrastromal ring-had moderate values. Point spread function, MTF, and convolution acuity charts are presented for each eye, with the latter two showing improved visual function in the implanted eye, despite a higher aberration value. CONCLUSION: The wavefront measurement device captured aberrations even in a highly aberrated eye. Despite better UCVA and BSCVA, the Ferrara ring notably increased higher order aberrations compared to the fellow eye, but with a more uniform central pattern. In this case, the larger RMS value was a poor predictor of good visual function; other metrics better predicted the patient's subjective response. Metrics other than RMS error may be necessary to better correlate aberration value with visual satisfaction in some eyes. [J Refract Surg 2004;20:823-830]

The introduction of wavefront sensing technology and customized corneal ablation has revolutionized the field of refractive surgery. Yet, in order for customized laser vision correction to reach its full potential, a number of technological requirements must be addressed by the specific laser vision correction platform offering this customized procedure. At present,several different technology platforms exist. A more thorough understanding of these platforms will help in evaluating which system is best at eliminating aberrations. The following technology is required to provide what is considered optimal within the current state of knowledge in this field: (1) scanning spot laser delivery, (2) robust eye tracking,(3) an accurate wavefront device, and (4) the wavefront-laser interface.

Purpose To evaluate the information assessed with the LADARWave wavefront measurement device and correlate it with visual symptoms, refraction, and corneal topography in previously LASIK-treated eyes. Participants One hundred five eyes (58 patients) of individuals who underwent LASIK surgery were evaluated. Design Retrospective, noncomparative case series. Main outcome measures Complete ophthalmologic examination, corneal topography, and wavefront measurements were performed. Correlations were made between the examinations and symptoms. Methods Wavefront measurements were assessed with the LADARWave device. Manifest, cycloplegic refraction, and topographic data were compared with wavefront refraction and higher order aberrations. Visual symptoms were correlated to higher order aberrations in 3 different pupil sizes (5-mm, 7-mm, and scotopic pupil size). Pearson's correlation coefficient and generalized estimating equations were used for statistical analysis. Results In post-LASIK eyes, wavefront refraction components were poorly correlated to manifest and cycloplegic components. The comparison between manifest, cycloplegic, and wavefront refraction with total amount of higher order aberrations showed no strong correlation. The comparison between topography and manifest, cycloplegic, and wavefront refraction did not show strong correlation. Visual symptoms analysis showed correlation of double vision with total coma and with horizontal coma for the 5-mm and 7-mm pupil size; correlation between starburst and total coma for the 7-mm pupil size; and correlation of double vision with horizontal coma, glare with spherical aberrations and with total aberrations, and starburst with spherical aberrations for the scotopic pupil size. Scotopic pupil size had a positive association with starburst and a negative association with double vision. Conclusions The LADARWave wavefront measurement device is a valuable diagnostic tool in measuring refractive error with ocular aberrations in post-LASIK eyes. A strong correlation between visual symptoms and ocular aberrations, such as monocular diplopia with coma and starburst and glare with spherical aberration, suggest this device is valuable in diagnosing symptomatic LASIK-induced aberrations. Horizontal coma was correlated with double vision, whereas vertical coma was not.

To compare flap thickness and reproducibility of four different types of microkeratomes during LASIK.Retrospective, nonrandomized, comparative case series.Four hundred ninety consecutive eyes underwent LASIK and were evaluated by measuring the central flap thickness by subtractive pachymetry.All flaps were created using the BauschLomb (Miami, FL) Hansatome 180 head, the Alcon (Fort Worth, TX) Summit Krumeich Barraquer Microkeratome 160 head, the Moria (Antony, France) Carriazo Barraquer (CB) 130 head, or the Moria M2 110 head.The flap thickness measurements differed according to the microkeratome used and were 131+/-28 microm in 41 eyes (8.4%) with the BauschLomb Hansatome 180 head, 162+/-21 microm in 127 eyes (25.9%) with the Alcon Summit Krumeich Barraquer Microkeratome (SKBM) 160 head, 157+/-40 microm in 65 eyes (13.3%) with the Moria CB 130 head, and 134+/-23 microm in 257 eyes (52.4%) with the Moria M2 110 head. The central flap thickness with the SKBM and Moria M2 was statistically significantly more reproducible than with the Moria CB (P0.0005). There is no correlation between flap thickness reproducibility and age, corneal thickness, or corneal keratometric values. However, considering all the microkeratomes, female gender had statistically significantly more variability than male gender (P0.02).Based on these results, the greatest predictability of flap thickness was seen with the SKBM and Moria M2 microkeratomes, which both use a second motor for advancement. The greatest variability, noted with the Moria CB, was likely due to the manual translation feature and places further importance on the safety of the second motor and automation when performing LASIK.

Customized corneal ablation is an exciting frontier in refractive surgery that incorporates wavefront technology to detect and correct higher order aberrations in addition to spherocylindrical refractive errors. The goal is to achieve super normal vision in terms of acuity and contrast. As the concept of wavefront customized ablations is still new, there are a number of aspects of its clinical application that need analysis and understanding. Numerous reports have appeared in the literature during the past year that address the developments, concerns, and limitations of wavefront technology and custom ablation. We have attempted to summarize and discuss the significant reports in this current review. Our focus is on the optical and physiologic limits of wavefront customized correction, including the effect of accommodation, aging, and flap creation on the aberration profile. In addition, we also present the laser technology requirements, and clinical outcomes of customized excimer ablations that are reported to date.

PUBPOSE: To evaluate refractive outcome and objective clinical data, and determine efficacy, predictability, and safety of laser epithelial keratomileusis (LASEK) for myopic treatments. METHODS: We performed a retrospective noncomparative single-surgeon case series on the first 20 LASER procedures (Alcon LADARVision 4000 laser). Mean patient age was 41.2 years (range 21 to 60 yr): 13 men and 7 women. Mean preoperative spherical equivalent refraction was -6.47±2.78 D. Corneal haze, uncorrected and spectacle-corrected visual acuity and manifest refraction were evaluated. RESULTS: Of 20 eyes studied, 3 were corrected for monovision. In the non-monovision group, 20/40 or better visual acuity was achieved in 94% (16 eyes) at 1 month, 100% (13 eyes) at 3 months, and 91% (10 eyes) at 6 months after LASEK; 20/20 or better was achieved in 12% (2 eyes) at 1 month, 46% (6 eyes) at 3 months, and 45% (5 eyes) at 6 months. Corneal haze at 1 month was grade 0.5 in 35% (7 eyes), 1 in 20% (4 eyes) and 2 in 10% (2 eyes). At 3 months, 62% (12 eyes) had grade 0.5 and 31% (6 eyes) had grade 1. At 6 months, 58% (12 eyes) had grade 0.5, 25% (5 eyes) had grade 1, and 8% (2 eyes) had grade 2. CONCLUSIONS: LASEK is a challenging procedure. Creating the epithelial flap is not simple and may have contributed to the high haze incidence in our study. [J Refract Surg 2003;19:412-415]

Purpose To report a flap-related complication that occurs when a secondary microkeratome pass interferes with the pathway of a complicated first microkeratome pass. Design Small, retrospective, noncomparative, interventional case series. Participants Three patients. Methods In three cases, each patient experienced a different flap-related complication with the original surgery, followed by interference of a secondary flap with the primary. The first patient experienced a free cap, followed by an interference of the secondary flap at the nasal portion of the free cap. The second patient experienced a buttonhole, followed by secondary flap interference in the superior quadrant adjacent to the buttonhole. The third patient experienced a decentered flap originally, followed by secondary flap interference temporally. Main outcome measures Visual result after secondary microkeratome-induced flap-related complications. Results All three patients had poor best spectacle-corrected visual acuity on the first postoperative day, with subsequent visual recovery. All three patients had induced flattening on keratometry along the axis where stromal tissue was removed. In addition, two patients required multiple enhancements to achieve desired visual outcomes. Conclusions Complications related to the primary microkeratome pass add further risk for complications to arise during a second microkeratome pass. A secondary microkeratome pass should be attempted only if the original flap cannot be identified, if it is the result of primary flap complication, or if the desired treatment zone is notably larger than the diameter of the original flap. Intraoperative pachymetry of the residual stromal bed should be performed routinely. It is important to examine the stromal bed closely for loose or displaced slivers of tissue and to remove them before excimer treatment.

PURPOSE: To clarify the feasibility of aberration-sensing and wavefront-guided laser in situ keratomileusis (LASIK) to manage grossly decentered ablation and to discuss the limitations of the technology. METHODS: Three patients with previous decentrations of the ablation zone between 1.5 to 2.0 mm were scheduled for wavefront-guided LASIK. AU patients reported monocular diplopia and halos. Wavefront aberrations were measured with a Tscherning-type aberrometer. Laser ablation was done with a WaveLight Allegretto in a one-step procedure with ablation profiles calculated only from the individual wavefront map. Decentrations were determined from corneal topography. RESULTS: Three months after surgery, patient WM and patient SU had gained uncorrected and best spectacle-corrected visual acuity. The root mean square-wavefront error decreased up to 61% and 33%, respectively, for total and higher order aberrations (Zernike modes of 3rd order and higher). There was significant enlargement of the optical zone determined by corneal topography, and both patients no longer reported diplopia and halos at 3 months postoperatively. The optical aberration of the third patient (RE), after a 5.00-D overcorrection with a 2-mm decentratici!, was too high for aberration-sensing; retinal images obtained from the wavefront device were too smeared and not of sufficient contrast. In addition, this patient had a residual corneal thickness of 416 µm and thus wavefront-guided LASEK was not done. CONCLUSIONS: Wavefront-guided LASIK offers a new way of managing grossly decentered laser ablations. Unfortunately, there are still patients who have aberrations too large for wavefront sensing or with other clinical limitations such as a residual corneal thickness too thin for further treatment. [J Refract Surg 2002;18:418-429]

We describe the case of a 50-year-old woman with anterior basement membrane dystrophy and dry eyes who had femtosecond laser in situ keratomileusis (LASIK) with gas-bubble breakthrough during flap creation in both eyes. The gas-bubble breakthrough appeared beneath the applanation interface in advance of the leading laser edge in the right eye and behind the advancing laser edge in the left eye. The surgery was aborted and 5 days later, photorefractive keratectomy with mitomycin-C was performed in the right eye and LASIK in the left eye. When a gas-bubble breakthrough extends in front of the advancing laser edge of the flap, the surgery should be aborted; surface ablation can be performed as a second-stage procedure. However, if the breakthrough occurs behind the advancing laser edge, the flap can be carefully lifted and the LASIK completed. Financial Disclosure Dr. Krueger is a consultant to Alcon Laboratories, Inc. Dr. Ribeiro has no financial or proprietary interest in any material or method mentioned.

Purpose: To study the effect of timolol maleate, dorzolamide, or a combination of both in post photorefractive keratectomy (PRK) eyes with an elevated intraocular pressure (IOP) after topical steroid administration. Setting: Refractive Surgery Outpatient Department, 1st Department of Ophthalmology, Semmelweis University, Budapest, Hungary. Methods: Forty-five patients with elevated IOP were randomly enrolled in 3 groups: Group 1 received timolol maleate 0.5% twice a day; Group 2 received timolol maleate 0.5% twice a day and dorzolamide 2% 3 times a day; and Group 3 received only topical dorzolamide 2% 3 times a day. Intraocular pressure was measured 3 days and 1, 3, and 6 weeks after the antiglaucoma medication was started. Results: The mean preoperative IOP was 15.25 mm Hg ± 1.28 (SD). Following administration of topical fluorometholone, the IOP increased a mean of 27.39 ± 2.88 mm Hg. Six weeks after the antiglaucoma therapy was started, the mean IOP reduction was 6.6 mm Hg in Group 1, 8.86 mm Hg in Group 2, and 4.64 mm Hg in Group 3. Conclusions: A combination therapy of timolol 0.5% and dorzolamide 2% was most effective in treating secondary IOP elevation after PRK. Dorzolamide alone did not adequately control secondary post-PRK IOP elevation.

Purpose To determine the stress wave amplitudes generated during photoablation of the cornea using an argon fluoride excimer laser. Design Experimental study using porcine eyes. Methods Profiles of the stress wave amplitudes and enucleated human eyes along the axis of symmetry of porcine eyes and enucleated human eyes were measured using a miniature piezoelectric transducer. The ablation parameters, fluence, and ablation diameters were varied within the range of clinical application. Main outcome measures Stress wave amplitudes generated during photoablation. Results The stress waves pass through a pressure focus located in the posterior lens and anterior vitreous, where amplitudes of up to 100 atm were measured with a 6-mm or larger ablation zone. Posterior to this focus, the stress wave amplitudes rapidly decrease to less than 10 atm at the retinal site. Small diameter excimer laser spots (≤1.5 mm) produce a declining stress wave with no pressure focus at the lens and anterior vitreous. Conclusions Stress waves may be potentially hazardous to anterior structures of the human eye, including the corneal endothelium, lens and anterior vitreous face. They peak at the lens and vitreous with a broad beam, but not with small spot laser ablation. At posterior retinal and subretinal structures, they may be considered harmless.

Purpose A new form of aberrometry based on Tscherning optics has been proposed that captures the refraction and high-order aberrations of the eye with and without accommodation. Design Experimental clinical optics study. Method A green neodymium:yttrium–aluminum–garnet laser grid pattern is projected into the eye and viewed on the retina through a narrow, collimated aperture of 1 mm. The resulting aberrated pattern is photographically recorded in a normal eye in the unaccommodated and accommodated state through a pharmacologically dilated pupil without cycloplegia. Main outcome measures Detection of pupil-dependent refraction and high-order optical aberration with and without accommodation. Results Subtle pupil-dependent errors in refraction and high-order aberrations (spherical aberrations and coma) are demonstrated in the unaccommodated normal eye. Accommodation reveals slightly more spherical power through the central 3-mm zone than through a 6.5-mm pupil without significant increase in aberration. Conclusions Tscherning aberrometry based on ‘retinal imaging' is useful in defining the refraction and optical aberrations in a normal eye. Accommodation increases spherical refractive power with only small aberration changes, including negative asphericity.

Purpose To assess the predictive accuracy of simulation-based LASIK outcomes. Methods Preoperative and 3-month post-LASIK tomographic data from 20 eyes of 12 patients who underwent wavefront-optimized LASIK for myopia were obtained retrospectively. Patient-specific finite element models were created and case-specific treatment settings were simulated. Simulated keratometry (SimK) values and the mean tangential curvature of the central 3 mm (Kmean) were obtained from the anterior surfaces of the clinical tomographies, and computational models were compared. Correlations between Kmean prediction error and patient age, preoperative corneal hysteresis (CH), and corneal resistance factor (CRF) were assessed. Results The mean difference for Kmean between simulated and actual post-LASIK cases was not statistically significant (−0.13 ± 0.36 diopters [D], P = 0.1). The mean difference between the surgically induced clinical change in Kmean and the model-predicted change was −0.11 ± 0.34 D (P = 0.2). Kmean prediction error was correlated to CH, CRF, and patient age (r = 0.63, 0.53, and 0.5, respectively, P < 0.02), and incorporation of CH values into predictions as a linear offset increased their accuracy. Simulated changes in Kmean accounted for 97% of the variance in actual spherical equivalent refractive change. Conclusions Clinically feasible computational simulations predicted corneal curvature and manifest refraction outcomes with a level of accuracy in myopic LASIK cases that approached the limits of measurement error. Readily available preoperative biomechanical measures enhanced simulation accuracy. Patient-specific simulation may be a useful tool for clinical guidance in de novo LASIK cases.

PURPOSE: To characterize the surgicallyinduced-astigmatism (SIA) associated with spherical LASIK. METHODS: Refractive outcomes in 70 eyes that underwent primary myopic LASIK with purely spherical ablation were analyzed. The Summit Apex Plus excimer laser was used. The Bausch & Lomb Hansatome with the 180-µ?? plate was used to produce superiorly hinged flaps. The relationship between refractive astigmatism and corneal topographic astigmatism was analyzed using linear regression and vector analysis. RESULTS: There was a statistically significant negative correlation (slope = -0.21) between refractive surgically-induced astigmatism and preoperative topographic cylinder. A 0.24-D with-the-rule shift was also found. Surgically-induced astigmatism was not correlated with the magnitude of laser ablation. CONCLUSION: The lamellar keratotomy portion of LASIK reduces pre-existing corneal astigmatism and produces a relative steepening of the hinge meridian. [J Refract Surg 2000;16:515-518]

Purpose To evaluate the accuracy and repeatability of the pupil-measuring modules of several corneal topography devices. Setting Department of Ophthalmology, Saint Louis University Eye Institute, St. Louis, Missouri, USA. Methods In 14 eyes of 7 healthy myopic patients, pupillometry was performed with 3 corneal topography devices and with an infrared pupillometer under luminance-matched conditions for the Placido projection of the topography devices. Pupils were also measured under a mesopic condition. Outcomes were pupil diameters, limits of agreement, and coefficient of repeatability of the topography devices. Results Mean pupil diameter measurements with the Technomed C-Scan, Humphrey Masterview, Alcon EyeMap, and under a mesopic condition were 3.35 mm, 2.96 mm, 2.34 mm, and 5.94 mm, respectively. All pupil diameter measurements differed significantly from one another except those by the Masterview and C-Scan devices. The mean difference between the C-Scan and luminance-matched infrared measurements was 0.74 mm and between the Masterview and luminance-matched infrared measurements, 0.27 mm. The limits of agreement ±2 standard deviations was 4.12 mm and 1.56 mm for the C-Scan and Masterview devices, respectively. Coefficients of repeatability were 0.56 mm, 0.46 mm, and 0.44 mm for the C-Scan, Masterview, and EyeMap devices, respectively. Conclusions Although topography pupillometry was repeatable, it underestimated the largest natural pupil diameter because of the luminance of the Placido rings. The difference in limits of agreement between the C-Scan and Masterview devices may be explained by pupil physiology and the static nature of videokeratoscopy. These results have implications when topography pupillometry is used to assess pupil diameters prior to refractive surgery. We do not recommend using pupil diameters measured by topography to preoperatively determine halo-related safety.

In dealing with refractive surgery as a subspecialty, a thorough understanding of the optical properties of the eye and corneal surface measurements are necessary. This foundational information allows us to understand the optics of laser vision correction and laser in situ keratomileusis (LASIK). Also, the customization of LASIK with topography or wavefront sensing allows us to look at the optics of refractive surgery in a whole new light. Understanding aberrations and how they may be corrected will allow us to achieve a potential for better visual acuity than a patient's best corrected acuity naturally. This article addresses the most important issues regarding the optics of refractive surgery

To evaluate the effect of a glare source on visual function in patients after photorefractive keratectomy and radial keratotomy.Thirteen patients (22 eyes) who underwent photorefractive keratectomy and 20 patients (40 eyes) who underwent radial keratotomy were evaluated in this cross-sectional study. LogMAR visual acuity and contrast sensitivity were measured. Pupils were measured with the Rosenbaum card. A halogen/tungsten glare source approximated the luminance of headlights of an oncoming car at 100 feet.In the photorefractive keratectomy and radial keratotomy groups, pupils were significantly smaller (P.01) and the pupillary clearance of the ablation zone in photorefractive keratectomy and the clear zone in radial keratotomy were significantly larger under the glare condition (P.01). In the photorefractive keratectomy group, visual acuity and contrast sensitivity under the glare condition were significantly higher than in the no-glare condition (P = .02). In the radial keratotomy group, contrast sensitivity under the glare condition was significantly higher than under the no-glare condition (P = .001 to .003).After photorefractive keratectomy or radial keratotomy, the traditional glare source constricted the pupil and partially masked the optical aberrations, which resulted in an improvement in visual function. A "pupil-sparing" aberration test is needed for evaluation of visual function after refractive surgery.

Purpose: To evaluate the relationship between contrast sensitivity, surgical treatment zone, and clearance (ablation or clear zone — pupil diameter), photorefractive keraectomy (PRK) and radial keratotomy (RK). Setting: Saint Louis University Eye Institute St. Louis, Missouri, and Hunkeler EyeCenter, Kansas City, Missouri, USA. Methods: Thirteen patients had PRK and 20, RK. Contrast sensitivity was measured with the Stereo Optical F.A.C.T. (F.A.C.T.) and VectorVision CSV 1000 (V.V) charts Pupils were measured with the Rosenbaum card. Results: In the PRK group, W contrast sensitivity at 6 and 12 cycles per degree(cpd) correlated withthe ablation zone ( r 2 = 0 18 and 0.22, respectively) while visual acuity and F.A.CT. contrast sensitivity did not correlate. In the RK group both W and F.A.C.T. contrast sensitivity contrast sensitivity at 6 cpd correlated with clearance ( r 2 = 0.29 and 0.12, respectively). Pupils were larger with the W test than with the F.A.C.T. chart because ambient chart luminance was less in the former Conclusion: Contrast sensitivity is likely a more sensitive indicator of visual function than acuity in refractive surgery. The W system unmasks aberrations, from the transition zone of ablated and unablated. cornea in PRK ; Larger samples are needed to determine the critical ablation clearance of the pupil to avoid loss of visual function.