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Neel S Vaidya,1,2 Arvin Daneshmand,3 Randy J Epstein,1,2 Parag A Majmudar,1,2 Michael W Belin,4,5 Edward C Parsons,5 Roy S Rubinfeld5– 7 1Chicago Cornea Consultants, Highland Park, IL, USA; 2Department of Ophthalmology, Rush University Medical Center, Chicago, IL, USA; 3Georgetown University Medical School, Washington, DC, USA; 4Department of Ophthalmology, University of Arizona, Tucson, AZ, USA; 5CXL Ophthalmics, LLC, Encinitas, CA, USA; 6Department of Ophthalmology, Georgetown University Medical School/Washington Hospital Cente, Washington, DC, USA; 7Re:Vision Private Practice, Rockville, MD, USACorrespondence: Neel S Vaidya, Chicago Cornea Consultants, 806 Central Ave Suite 300, Highland Park, IL, 60035, USA, Email nsv@chicagocornea.comPurpose: To assess the change in corneal pachymetry after a novel epithelium-on (EpiSmart®) corneal crosslinking procedure (CXL).Methods: Eyes treated as part of the open-label, non-controlled arm of the study “Collagen Crosslinking with Ultraviolet-A in Asymmetric Corneas” (NCT01097447) were examined at baseline, 3-, 6- and 12-months post-CXL. Thinnest pachymetry readings based on Pentacam (OCULUS GmbH, Wetzlar, Germany) were recorded.Results: A total of 101 eyes met the study inclusion criteria. Thinnest pachymetric readings at baseline averaged 451 ± 50 microns. The mean (± SD) minimum thickness was 450 ± 46 microns at 3 months, 452 ± 47 microns at 6 months, and 451 ± 48 microns at 12 months post-CXL. The changes from baseline (mean ± SE) at 3, 6, and 12 months post-CXL were − 1.2 ± 1.5 microns, 0.5 ± 1.6 microns, and 0.4 ± 1.6 microns, respectively. Student’s t-tests showed no statistically significant change in pachymetry from baseline for any exam period.Conclusion: This study demonstrated that, after EpiSmart® epithelium-on CXL, there was no substantial corneal thinning observable on Scheimpflug tomography out to 12 months.Keywords: corneal thinning, cross-linking, epithelium-on, keratoconus, pachymetry, post-surgical ectasia

Mazen M Sinjab,1,2 Roy S Rubinfeld,3,4 Kirsten Wagner,5,6 Edward C Parsons Jnr,7 Arthur B Cummings,8 Michael W Belin9 1Dr. Mazen Eye Clinic, Medcare Hospitals and Centres, Dubai, United Arab Emirates; 2Al Zahra Medical Group, Damascus, Syria; 3Department of Ophthalmology, Georgetown University Medical School/Washington Hospital Center, Washington, DC, USA; 4Re:Vision Private Practice, Rockville, MD, USA; 5Department of Ophthalmology, Medstar Georgetown University Hospital, Washington, DC, USA; 6Department of Ophthalmology, Medstar Washington Hospital Center, Washington, DC, USA; 7CXL Ophthalmics, Encinitas, CA, USA; 8Wellington Eye Clinic, Dublin, Ireland; 9Department of Ophthalmology, University of Arizona, Tucson, AZ, USACorrespondence: Roy S Rubinfeld 3131 Connecticut Ave, NW, #2809, Washington, DC, 20008, USAEmail Doctor@revisedeye.comPurpose: To assess the effectiveness of a novel treatment for patients with advanced corneal ectasia and loss of visual acuity (VA). Conductive keratoplasty (CK) is performed to improve VA followed by epithelium-on (epi-on) corneal crosslinking (CXL) to stabilize the cornea after CK.Methods: Retrospective, exploratory cohort study. Patients with keratoconus or postsurgical ectasia and best spectacle-corrected distance VA (CDVA) ≤ 20/40 were included. Conductive keratoplasty was performed (ViewPoint CK System, Refractec, Inc., Bloomington, MN); followed a day later by epi-on CXL (CXLUSA/CXLO, Bethesda, MD/CXLO Encinitas, CA). Measures included uncorrected distance visual acuity (UDVA) and CDVA, as well as refractive and tomographic measures and tomographic indices.Results: Data from 50 eyes of 45 patients were analyzed. Mean follow-up was 15.1 ± 12.2 months (range: 2 to 51). Overall, UDVA and CDVA improved postoperatively. Subjective refraction and tomographic metrics did not show consistent changes, but changes in tomographic indices were associated with treatment follow-up time. At the 1-year visit, mean UDVA significantly improved over baseline (P = 0.009) by approximately 3 lines; mean CDVA improved significantly (P = 10− 5) by approximately 2 lines. No eye lost lines of CDVA. Change in the Index of Surface Variance (ISV) was associated with treatment, and the D-Index trended over follow-up time.Conclusion: Conductive keratoplasty with a proprietary epi-on CXL treatment improved vision in patients with advanced ectasia This CK/epi-on CXL treatment offers the possibility of improved VA for patients with compromised vision due to ectasia.Keywords: conductive keratoplasty, CK, corneal crosslinking, crosslinking, keratoconus, ectasia, thermokeratoplasty

Instrument does not require viscoelastic, an anterior chamber maintainer or extensive intraocular tissue manipulation. [ABSTRACT FROM AUTHOR]

Accurate detection of post-refractive ectasia susceptibility is essential during preoperative evaluation for laser vision correction (LVC) due to the risk of progressive corneal ectasia and vision decline post-surgery. Despite improved screening and a reduced incidence from 0.66 to 0.033%, iatrogenic ectasia remains a concern due to the severe vision loss it can cause, highlighting the need for more accurate detection tools. A new optimized version of the Belin/Ambrósio Enhanced Ectasia Display version 4 (BAD-D v4) was developed and validated across 26 international centers to enhance the detection of keratoconus and very asymmetric ectasia and to assess the risk of post-refractive ectasia. Analyzing a dataset of 3,886 eyes from 3,351 patients, including normal, keratoconus (KC), and cases with very asymmetric ectasia (VAE) categories, having one eye with normal topography (VAE-NT and the fellow eye with clinical ectasia (VAE-E). The study utilized an optimized logistic regression algorithm improving diagnostic accuracy. The BAD-D v4 showed superior efficacy in differentiating normal eyes from ectatic conditions, with Area Under the Receiver Operating Characteristic Curve (AUROC) scores of 0.997 and 0.998 in training and testing samples for normal versus clinical ectasia. Additionally, in Normal vs. Disease (KC + VAE), the AUROC was 0.974 and 0.966, and in the challenging Normal vs. VAE-NT diverse group, it scored 0.905 and 0.858. These results outperformed the current version (BAD-D v3) and were comparable to the Pentacam Random Forest Index in all tested scenarios, highlighting the potential of BAD-D v4 in early ectasia detection, without altering the index scale or the end-user experience., Competing Interests: Declarations. Competing interests: BL, MB and RA are consultants for Oculus GmbH (Wetzlar, Germany), MH, LI and TK declare no potential conflict of interest., (© 2024. The Author(s).)

Introduction: The aim of the study was to report a unique case with excellent clinical outcomes after late endophthalmitis following Descemet's membrane endothelial keratoplasty (DMEK) surgery requiring donor graft removal without replacement., Case Presentation: A 67-year-old female with a prior ocular history of bilateral cataract surgery, Fuchs endothelial dystrophy, and pseudophakic DMEK in the left eye presented with endophthalmitis 2 months after keratoplasty. DMEK graft removal without replacement with an intracameral washout, pars plana vitrectomy, intracameral, and intravitreal antibiotics resulted in an excellent visual outcome (20/25)., Conclusion: This is a unique case of late endophthalmitis following DMEK surgery requiring graft removal and pars plana vitrectomy with excellent visual recovery without donor replacement., Competing Interests: The authors declare no conflict of interests., (© 2024 The Author(s). Published by S. Karger AG, Basel.)

Objectives: To compare astigmatism correction after photorefractive keratectomy (PRK) using three excimer laser devices, Alcon Wavelight EX500, Schwind Amaris 1,050, and Technolas Teneo317 M2., Methods: This retrospective study included 414 eyes from 414 subjects with a history of PRK performed using Alcon Wavelight (n=172), Schwind Amaris (n=122), and Technolas (n=120). Uncorrected & corrected distance visual acuity (UDVA & CDVA), and refractive status (spherical equivalent (SE) and vector analysis (J0 and J45)) were postoperatively recorded at the 6-month and 12-month examinations., Results: The mean CDVA and J45 at 6-month and 12-month showed no statistically significant difference among the three different excimer lasers ( P >0.05). There was a statistically significant difference in mean UDVA and J0 at 6-month and 12-month after PRK among the three groups, with no statistically significant difference between Alcon Wavelight and Schwind Amaris lasers, while both of the prior lasers showed a significant difference with the Technolas laser. The highest and lowest changes in the magnitude of J0 in 6-month and 12-month follow-ups were seen for the Alcon Wavelight and Technolas groups, respectively. Both Schwind Amaris and Technolas had a small hyperopic SE while the Alcon Wavelight's SE was minimally myopic. This difference in SE between Alcon Wavelight and both Schwind Amaris and Technolas reached statistical significance., Conclusion: While all three lasers performed well in reducing preoperative astigmatism; however, the Alcon Wavelight and Schwind Amaris were more effective in correcting astigmatism than the Technolas. The difference between the Alcon Wavelight and Schwind Amaris did not reach statistical significance., (Copyright © 2024 Contact Lens Association of Ophthalmologists.)

Purpose: To compare the corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic patterns., Methods: In this cross-sectional study, 144 eyes were divided based on inferior-superior asymmetry value (I-S) into symmetric (zero I-S: - 0.50 to + 0.50 D) and asymmetric bow-tie topographic patterns with inferior (positive I-S: + 0.51 to + 1.4 D) or superior (negative I-S: - 2.5 to - 0.51 D) steepening. The biomechanical assessment was performed using Corvis ST and ocular response analyzer (ORA). A general linear model univariate analysis was used to compare the parameters, while the central corneal thickness, intraocular pressure, and age were considered covariates., Results: Only the peak distance (PD) at the highest concavity phase (P = 0.007) and tomographic biomechanical index (TBI, P = 0.001) showed statistically significant differences between the three groups. For TBI, this difference was statistically significant between the positive I-S group separately with the zero I-S group (P < 0.001), and with the negative I-S group (P = 0.022). For PD, the significant difference was between the negative I-S group separately with zero I-S (P = 0.019), and positive I-S groups (P = 0.018). There was a statistically significant correlation between the I-S value with PD (r = 0.281, P = 0.001) and TBI (r = 0.170, P = 0.044)., Conclusions: Most corneal biomechanical parameters are not statistically significant compared to the zero I-S group. However, superior steepening is associated with a stiffer response based solely on the shorter PD values seen in this group, and the group with the inferior steepening shows the highest or more suspicious values based on TBI., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Purpose: To optimize artificial intelligence (AI) algorithms to integrate Scheimpflug-based corneal tomography and biomechanics to enhance ectasia detection., Design: Multicenter cross-sectional case-control retrospective study., Methods: A total of 3886 unoperated eyes from 3412 patients had Pentacam and Corvis ST (Oculus Optikgeräte GmbH) examinations. The database included 1 eye randomly selected from 1680 normal patients (N) and from 1181 "bilateral" keratoconus (KC) patients, along with 551 normal topography eyes from patients with very asymmetric ectasia (VAE-NT), and their 474 unoperated ectatic (VAE-E) eyes. The current TBIv1 (tomographic-biomechanical index) was tested, and an optimized AI algorithm was developed for augmenting accuracy., Results: The area under the receiver operating characteristic curve (AUC) of the TBIv1 for discriminating clinical ectasia (KC and VAE-E) was 0.999 (98.5% sensitivity; 98.6% specificity [cutoff: 0.5]), and for VAE-NT, 0.899 (76% sensitivity; 89.1% specificity [cutoff: 0.29]). A novel random forest algorithm (TBIv2), developed with 18 features in 156 trees using 10-fold cross-validation, had a significantly higher AUC (0.945; DeLong, P < .0001) for detecting VAE-NT (84.4% sensitivity and 90.1% specificity; cutoff: 0.43; DeLong, P < .0001) and a similar AUC for clinical ectasia (0.999; DeLong, P = .818; 98.7% sensitivity; 99.2% specificity [cutoff: 0.8]). Considering all cases, the TBIv2 had a higher AUC (0.985) than TBIv1 (0.974; DeLong, P < .0001)., Conclusions: AI optimization to integrate Scheimpflug-based corneal tomography and biomechanical assessments augments accuracy for ectasia detection, characterizing ectasia susceptibility in the diverse VAE-NT group. Some patients with VAE may have true unilateral ectasia. Machine learning considering additional data, including epithelial thickness or other parameters from multimodal refractive imaging, will continuously enhance accuracy. NOTE: Publication of this article is sponsored by the American Ophthalmological Society., (Copyright © 2022. Published by Elsevier Inc.)

Purpose: The aim of this study was to assess changes in visual acuity after epithelium-on ("epi-on") corneal crosslinking after a diagnosis of keratoconus., Methods: Subjects with corneal ectatic diseases were enrolled in a prospective, randomized, controlled, open-label, multicenter trial. Subjects were randomized to 1 of 3 treatment groups and treated with an epi-on crosslinking system including riboflavin/sodium iodide and pulsed UVA exposure (EpiSmart, CXL Ophthalmics, Encinitas, CA). The UVA treatment groups were 2.4 J/cm 2 over 20 minutes, 3.6 J/cm 2 over 20 minutes, and 3.6 J/cm 2 over 30 minutes. The primary end point was logarithm of the minimum angle of resolution corrected distance visual acuity (CDVA). Secondary end points were logarithm of the minimum angle of resolution uncorrected distance visual acuity (UCVA), maximum corneal curvature (Kmax), and minimum corneal thickness. Data were assessed 6 and 12 months post-operatively, using t -tests for differences from baseline., Results: Two thousand two hundred twenty-eight subjects were treated with epi-on crosslinking. One thousand nine hundred twenty-two subjects had a diagnosis of keratoconus; other treated eyes had postsurgical and other ectasias. At 6 and 12 months, the subjects with keratoconus demonstrated significant improvements in CDVA, UCVA, and Kmax; minimum corneal thickness was unchanged. One hundred ninety-five subjects (8.7%) reported at least 1 adverse event (AE). A mild corneal epithelial defect was reported in 31 cases (1.4%) and was the only AE reported in >1% of subjects. There were no serious AEs related to the treatment., Conclusions: EpiSmart epi-on crosslinking resulted in mean improvements in CDVA, UCVA, and Kmax at both 6 and 12 months and an excellent safety and efficacy profile in subjects with keratoconus, with few significant side effects. Differences between UVA treatment groups were not significant., Competing Interests: R. S. Rubinfeld, D. Gravemann, R. Littner, and M. W. Belin have equity interests in CXL Ophthalmics, LLC, Encinitas, CA. M. W. Belin is a consultant to OCULUS GmbH, Wetzlar, Germany. The remaining author has no conflicts of interest to disclose., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc.)

Purpose: The purpose of this study was to evaluate postoperative Scheimpflug imaging changes during the first 5 years after penetrating keratoplasty (PK) in patients with keratoconus (KC)., Methods: This retrospective, interventional case series includes 31 eyes of 31 patients who underwent their first PK with a history of KC. Postoperative Scheimpflug imaging was performed 3 months after the removal of the last suture (baseline) and then repeated 3 and 5 years after the PK. Demographic data, donor and host trephination diameter, and Scheimpflug imaging (Pentacam HR, Oculus, Germany) parameters indicative of ectasia were analyzed to evaluate postoperative graft changes that occur after PK., Results: The maximal keratometry (Kmax) progressed significantly between baseline (53.5 ± 6.1 D) and postoperative year 3 and year 5 [56.5 ± 6.1 diopter (D) and 58.8 ± 7.9 D, P < 0.001]. Significant changes were also observed for the anterior best fit sphere and posterior best fit sphere ( P < 0.001 for 3 and 5 years compared with baseline). Kmax increased by at least 2 Ds for 74.2% of patients and up to 7 Ds or more for 25.8% of the patients. A significant inverse correlation was observed for host trephine size and progression of Kmax (r = -0.52, P = 0.01), which indicated that larger host trephination size was associated with a smaller increase in postoperative Kmax., Conclusions: Tomographic graft changes indicative of ectasia were observed within 3 to 5 years after PK in patients with KC. These changes were observed more frequently and sooner after corneal transplants than previously reported., Competing Interests: Conflicts of interest statement: The authors have no funding or conflicts of interest to disclose., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: To assess the reliability of successive Corvis ST® measurements (CST, Oculus, Wetzlar, Germany) in keratoconus (KC) ≥ 2 years after accelerated corneal crosslinking (9 mW/cm 2 , 10 min, 5.4 J/cm 2 ) compared to untreated KC corneas., Methods: Three successive CST measurements per eye were performed in ≥ 2 years after CXL (CXLG, n = 20 corneas of 16 patients) and a control group consisting of non-operated, ABC-stage-matched KC corneas according to Belin's ABCD KC grading (controls, n = 20 corneas, 20 patients). Main outcome measures included maximal keratometry (Kmax), the Belin/Ambrósio-Enhanced-Ectasia-Deviation-Index BAD-D; the biomechanical parameters A1 velocity, deformation amplitude (DA) ratio 2 mm, Ambrósio relational thickness to the horizontal profile (ARTh), integrated radius, stiffness parameter A1 (SP-A1), and the Corvis Biomechanical Factor (CBiF, the linearized term of the Corvis Biomechanical Index). Mean values, standard deviations, and Cronbach's alpha (CA) were calculated., Results: Both groups were tomographically comparable (BAD: 11.5 ± 4.7|11.2 ± 3.6, p = 0.682, Kmax: 60.5 ± 7.2|60.7 ± 7.7, p = 0.868 for controls|CXLG, paired t-test). A1 velocity (mean ± SD: 0.176 ± 0.02|0.183 ± 0.02, p = 0.090, CA: 0.960|0.960), DA ratio 2 mm (6.04 ± 1.13|6.14 ± 1.03, p = 0.490, CA: 0.967|0.967), integrated radius (12.08 ± 2.5|12.42 ± 1.9, p = 0.450, CA: 0.976|0.976), and CBiF (4.62 ± 0.6|4.62 ± 0.4, p = 0.830, CA: 0.965|0.965) were also comparable (controls|CXLG). ARTh was significantly higher in controls (177.1 ± 59, CA: 0.993) than after CXL (155.21 ± 65, p = 0.0062, CA: 0.993) and SP-A1 was significantly higher after CXL (59.2 ± 13, CA: 0.912) than in controls (52.2 ± 16, p = 0.0018, CA: 0.912)., Conclusion: ARTh and SP-A1 differed significantly between controls and CXLG. Biomechanical measurements were generally of excellent reliability in both groups. CXL seems to affect biomechanical measurements of human corneas over more than 2 years., (© 2022. The Author(s).)

Purpose: This retrospective cross-sectional study evaluated the potential of an additional biomechanical parameter 'E' as an addition to the tomographic ABCD ectasia/keratoconus (KC) staging., Methods: The Corvis Biomechanical Factor (CBiF) represents the modified linear term of the Corvis Biomechanical Index (CBI) developed based on 448 KC corneas from the Homburg Keratoconus Center (HKC). The CBiF range was divided into five stages (E0 to E4) to create a grading system according to the ABCD stages. Stage E0 was characterized by values smaller than the 2.5 percentile. The thresholds were created by dividing the CBiF range between the 2.5 and 97.5 percentiles into four groups of equal values (E1-E4). The frequency distribution of 'E' was analysed and independently validated based on another 860 KC corneas dataset from Milano and Rio de Janeiro (MR). The relationship between 'E' and the ABCD staging was analysed by cross-tabulation. The specificity of 'E' was assessed based on healthy controls (112|851) from both datasets (HKC|MR)., Results: 'E' was normally distributed with E0 = 37|30, E1 = 86|200, E2 = 155|354, E3 = 101|206, E4 = 69|70 in the KC group and 96.4%|90.5% of the controls classified E0 in the HKC|MR dataset, respectively. Cross-tabulation revealed that 'E' was most comparable to posterior corneal curvature ('B') in both datasets, while showing a trend towards more advanced stages in comparison to anterior corneal curvature ('A') and thinnest corneal thickness ('C')., Conclusion: The novel Corvis-derived parameter 'E' provides a biomechanical staging for ectasia/KC potentially enhancing the ABCD staging and may detect abnormalities before tomographic changes, which requires further studies., (© 2021 The Authors. Acta Ophthalmologica published by John Wiley & Sons Ltd on behalf of Acta Ophthalmologica Scandinavica Foundation.)

Purpose: The purpose of this article was to study the impact of instillation of 1% fluorescein and mydriatics on measurements made by Scheimpflug imaging., Methods: This was a cross-sectional study of patients who had measurements of corneal shape (maximum keratometry and best fit sphere of anterior and posterior corneal surfaces), pachymetry (at the pupil center, corneal apex, and thinnest location), and anterior chamber parameters (depth, volume, and angle of anterior chamber and corneal volume) using the Pentacam HR before and after the instillation of fluorescein and mydriatics. Group A had baseline measurements that were repeated 1.5 hours after the instillation of 1% fluorescein and 0.8% tropicamide+ 5% phenylephrine eye drops. Group B had baseline measurements that were repeated 10 minutes after the instillation of 1% fluorescein, and group C had baseline measurements that were repeated 1.5 hours after the instillation of mydriatics., Results: Overall, 131 eyes of 131 patients were studied: 87 in group A, 28 in group B, and 16 in group C. Significant differences and wide variations were noted in corneal pachymetry and anterior chamber parameters in all 3 groups. The highest magnitude and range of difference was observed in pachymetry at the pupil center (17 ± 53.5 μm) and in anterior chamber volume (26.7 ± 69.8 mm 3 ). Corneal shape measurements of anterior and posterior corneal surfaces were not significantly affected by either fluorescein or mydriatics. Pupillary dilation also affected the ability of the Pentacam to accurately trace the pupil margin in 19.5% of cases., Conclusions: For consistent and accurate measurements, it is important that Scheimpflug imaging be performed before other tests which may need the instillation of fluorescein or mydriatics., Competing Interests: M. W. Belin and R. Ambrósio are consultants for Oculus Optikgeräte GmbH, Wetzlar, Germany. The remaining authors have no funding or conflicts of interest to disclose., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: To assess the change in corneal pachymetry after a novel epithelium-on (EpiSmart ® ) corneal crosslinking procedure (CXL)., Methods: Eyes treated as part of the open-label, non-controlled arm of the study "Collagen Crosslinking with Ultraviolet-A in Asymmetric Corneas" (NCT01097447) were examined at baseline, 3-, 6- and 12-months post-CXL. Thinnest pachymetry readings based on Pentacam (OCULUS GmbH, Wetzlar, Germany) were recorded., Results: A total of 101 eyes met the study inclusion criteria. Thinnest pachymetric readings at baseline averaged 451 ± 50 microns. The mean (± SD) minimum thickness was 450 ± 46 microns at 3 months, 452 ± 47 microns at 6 months, and 451 ± 48 microns at 12 months post-CXL. The changes from baseline (mean ± SE) at 3, 6, and 12 months post-CXL were -1.2 ± 1.5 microns, 0.5 ± 1.6 microns, and 0.4 ± 1.6 microns, respectively. Student's t-tests showed no statistically significant change in pachymetry from baseline for any exam period., Conclusion: This study demonstrated that, after EpiSmart ® epithelium-on CXL, there was no substantial corneal thinning observable on Scheimpflug tomography out to 12 months., Competing Interests: Drs. Majmudar, Belin, Parsons, and Rubinfeld have equity interests in CXL Ophthalmics, LLC, Encinitas, CA. Dr. Parsons is a consultant to CXL Ophthalmics, LLC, Encinitas, CA. Dr. Rubinfeld had a financial interest in CXLUSA, LLC, Bethesda, MD and reports open access fee from CXL Ophthalmics, LLC. Dr. Belin is a consultant to OCULUS GmbH. The authors report no other conflicts of interest in this work., (© 2022 Vaidya et al.)

Purpose: To investigate the relationship between corneal biomechanics and keratoconus (KC) severity as described by tomographic parameters., Setting: University-based German ophthalmology department., Design: Retrospective cross-sectional study., Methods: A total of 448 KC corneas of the Homburg Keratoconus Center and 112 healthy corneas (448+112 patients) were examined by Pentacam high-resolution and Corneal Visualization Scheimpflug Technology (Pentacam HR and Corvis ST). The KC population included a wide spectrum of disease severity based on Belin's ABCD classification. Linear regression analysis was performed between the linear term of the Corvis Biomechanical Index (CBI) (CBI beta) and the tomographic values anterior radius of curvature (ARC), posterior radius of curvature (PRC), and thinnest corneal thickness (TCT). A linear transformation of the CBI beta was performed to provide an intuitive scaling, which was referred to as the Corvis Biomechanical Factor (CBiF = -0.24294226 × CBI beta + 6.02). This scaling adjusted the CBI beta to the same scale as posterior corneal curvature (PRC)., Results: There was a high correlation of the CBI beta and its modification, the CBiF, with TCT (Pearson, r = -0.775), ARC (r = -0.835), and PRC (r = -0.839) in the KC population (P < .001). In the control corneas, the correlation between the CBI beta and ARC was weak (r = -0.216, P = .022), not significant (PRC, r = -0.146, P = .125), or moderate (TCT, r = -0.628, P < .001)., Conclusions: The linear term of the CBI was highly associated with KC severity as defined by corneal tomography. The CBiF represents a new scale based on biomechanical characteristics in KC, which could serve as a basis for a biomechanical KC classification in the future., (Copyright © 2021 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Abstract: The advent of refractive surgery and corneal cross-linking for ectatic disease has further highlighted the need to recognize early or subclinical ectatic disease. Historical systems depend on anterior corneal changes that occur late in the disease course and are commonly associated with visual loss. Tomographic imaging allows for the acquisition of posterior corneal surface data and corneal thickness distribution. This led to the development of modalities to diagnose early or subclinical keratoconus and to screen patients for refractive surgery.This article reviews the modern methods for assessing changes in posterior corneal surface and pachymetric distribution, now accepted by the major cornea societies to be the hallmarks of ectatic disease. Screening tools utilized by the commonly used tomographic imaging devices are discussed, and the difference between screening for ectasia and diagnosing keratoconus is highlighted. The Belin ABCD staging and classification system and the ABCD Progression Display are reviewed as a new grading and monitoring system that can be used for earlier intervention and prevention of visual loss in keratoconus., Competing Interests: M. W. Belin serves as a consultant to OCULUS GmbH. He receives no royalties for any of the software mentioned in this article. The remaining authors have no conflicts of interest to disclose., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose : To compare the corneal cone location on different maps and instruments, and their agreements, with elevation maps. Methods : In 90 left eyes with bilateral keratoconus, the apex of cone location was determined based on the maximum simulated keratometry (Kmax) location on the anterior sagittal curvature map by Pentacam HR, the maximum curvature on the mean curvature map by ATLAS 9000, most elevated point of the island of positive elevation relative to the best fit sphere on the front and back corneal elevation maps by Pentacam HR, and thinnest point on the thickness map by Pentacam HR and Orbscan, and the thinnest points on pachymetry and epithelial thickness maps by RTVue OCT. Results : There was a significant difference among the location on different maps along the x - and y -axes ( p < .001). The lowest agreement with the cone apex on both front and back elevation maps was for the anterior sagittal curvature map and the highest agreement for the Pentacam thickness map. The majority of keratoconus cone apexes were displaced in the inferotemporal direction on the different maps except for the epithelial thickness maps. Conclusions : Despite the variability between different devices and methods; the thickness map on the Pentacam HR showed the highest correlation with the front and back elevation maps, while the RTVue epithelial thickness map showed the poorest correlation. Based on this study, epithelial thickness maps and anterior curvature maps should be utilized with caution to determine the location of the cone.

Purpose: To assess corneal stability and corrected distance visual acuity (CDVA) 3, 6, and 12 months following corneal cross-linking (CXL) using the ABCD keratoconus staging system., Methods: This prospective longitudinal study included 31 eyes with keratoconus receiving CXL based on the standard Dresden protocol. CDVA, refraction, and Scheimpflug tomography with the Pentacam HR (Oculus Optikgeräte GmbH) were evaluated before and after surgery. Geometric and functional changes were assessed using the actual values and staging of each element of the ABCD keratoconus staging system. A, B, C, and D refer to the anterior and posterior radii of curvature in a 3-mm zone centered on the cor-neal thinnest point, minimum corneal thickness, and CDVA, respectively., Results: There were no significant changes in the actual values of anterior radius of curvature ( P = .497) and CDVA ( P = .082), whereas posterior radius of curvature ( P = .007) and corneal thinnest point ( P < .001) showed significant changes statistically. Pairwise comparison showed only a statistically significant steepening in posterior radius of curvature at 3 months after CXL compared to the preoperative radius ( P = .002) and a significant decrease in corneal thinnest point at 3 ( P < .001) and 6 ( P = .028) months after CXL compared to baseline assessment. Staging of each element of the ABCD keratoconus staging system indicated no change between baseline and 3, 6, and 12 months after CXL., Conclusions: The geometric and functional parameters included in the ABCD keratoconus staging system showed stability of corneal status and CDVA 1 year after CXL. [ J Refract Surg . 2021;37(10):700-706.] .

Purpose: To study the clinical, tomographic and densitometric features of eyes that showed >5 D of corneal flattening following collagen crosslinking (CXL) for progressive keratoconus and to identify preoperative predictive factors for such a response., Methods: This was a retrospective case control study of 548 eyes with progressive keratoconus which had undergone epithelium-off CXL (Dresden protocol) with a follow-up of 1 to 10 years. Eyes that showed ⩾5 D corneal flattening in maximum keratometry (Kmax) following CXL (group A) were compared with one eye of the remaining patients in the same cohort (group B). Changes in refraction and visual acuity, Kmax and thinnest pachymetry were compared between both groups. Univariate and multivariate regression analysis identified preoperative risk factors for unusual corneal flattening., Results: Forty three eyes in group A were compared with 502 eyes in group B. At the time of maximum flattening, group A showed more flattening (-7.6 ± 3.2 D) and thinning (-53.7 ± 45.2 µ) than group B (-1.69 ± 2.9 D and -26.6 ± 36.7 µ, respectively). Multivariate analysis based on parameters suggested by a univariate regression analysis identified pre-op Kmax to be the most significant predictor of intense corneal flattening. A subgroup analysis of K-matched eyes revealed that the duration of time following CXL was a significant risk factor for extreme corneal flattening following CXL., Conclusion: An intense corneal flattening >5 D in Kmax was documented in 7.85% of a cohort of keratoconus patients who underwent CXL. High preoperative Kmax and the duration of time following CXL were significant predictors of this response which was accompanied by significant corneal thinning.

Objective: To evaluate changes in visual acuity and corneal tomographic outcomes at 6 months after femtosecond-laser assisted implantation of two different types of intracorneal implants in keratoconus., Methods: A total of 39 keratoconus eyes implanted with two segments KeraRing ( n  = 22 eyes) or MyoRing ( n  = 17 eyes) were enrolled. Tomographic data (Pentacam system, Oculus) were analyzed and correlated with enhancement in uncorrected (UDVA) and corrected distance visual acuity (CDVA). The tomographic indices were front maximum keratometry (Kmax), corneal asphericity (Q-value) on both surfaces, average pachymetric progression indices (PPI), maximum Ambrosio relational thickness (ARTmax), Belin-Ambrósio enhanced ectasia total deviation index (BAD-D), index of surface variance (ISV), vertical asymmetry (IVA), height asymmetry (IHA) and height decentration (IHD)., Results: LogMAR UDVA and CDVA improved 2.1 ( p  = 0.003) and 0.7 ( p  = 0.074) lines with KeraRing, and 8 and 2.5 lines with MyoRing ( p  = 0.001). The highest and lowest mean differences in the tomographic indices between both groups were related to ISV and IHD, respectively. Changes in all indices differed significantly between two groups except for changes in front corneal astigmatism, ARTmax, ISV, IVA, IHD and IHA ( p  > 0.05). Correlation of changes in CDVA with changes in other parameters was statistically significant only for IHD in the KeraRing group, while changes in in UDVA were significantly correlated with changes in spherical equivalent, back Q-value, ISV, IVA, and IHA only in the MyoRing group., Conclusion: Both implants promote corneal shape regularization and an enhancement in UDVA in keratoconus. A considerable flattening effect and reduction in prolateness in the front corneal surface were observed with MyoRing.

Purpose: To evaluate the correlation between changes in maximum keratometry (Kmax) and ABC values from the ABCD Progression Display (Pentacam) in progressive keratoconus (KC) and to evaluate whether the ABC changes were able to detect progression earlier than Kmax., Setting: Humanitas Clinical and Research Center, Rozzano, Milan, Italy., Design: Retrospective study., Methods: Kmax, ABC values, and thinnest point (ThCT) were recorded at the day of corneal crosslinking (CXL) (T0) and previous follow-up (T-1). In patients without earlier progression in Kmax, follow-up examination (T-2) was used to determine whether any of the ABC parameters reached statistical significance for progression., Results: Seventy-six eyes of 63 patients scheduled for CXL with documented progression (Kmax increase of >1.00 diopter) were included. There was a significant, albeit moderate, correlation between the change in Kmax between T0 and T-1 and the change in both A (ρ = 0.391) and B values (ρ = 0.339). There was no significant correlation between the change in Kmax between T0 and T-1 and the change in either C or ThCT. In patients with T-2 examinations, 16 (51.6%) of 31 patients showed a statistically significant change on the ABCD progression display that was not detected with Kmax., Conclusions: This study showed a significant, but moderate, correlation between the change in Kmax and the change in A and B values in progressive KC. Moreover, more than half of the cases showed documented progression earlier with the ABCD progression display than that detected by standard Kmax changes. This study suggests possible changes in progression criteria to allow for earlier intervention., (Copyright © 2020 Published by Wolters Kluwer on behalf of ASCRS and ESCRS.)

Recent advances in the diagnosis and treatment of ectatic corneal disease have mandated a more modern staging system. The new Belin ABCD keratoconus staging system incorporates anterior and posterior curvature centered on the thinnest point of the cornea, thinnest pachymetry values and distance visual acuity in grades from 0-4. By including posterior curvature and thickness measurements based on the thinnest point, as opposed to apical, the new staging system better reflects anatomical changes seen in keratoconus and other ectatic diseases., Competing Interests: None

Before the advent of modern tomographic imaging and corneal cross-linking (CXL), diagnosis and treatment of ectatic disease were limited to disease severity where changes on the anterior corneal surface lead to visual complaints. Rigid contact lenses and/or penetrating keratoplasty addressed late stage disease, as identifying early or subclinical disease was not possible, or its need appreciated. The emergence of CXL as a viable treatment to alter the natural progression of keratoconus heightened the need for improved diagnostics.Several methods have been described in the literature to evaluate and document progression in keratoconus, but there has been no consistent definition of ectasia progression. Newer imaging techniques (ie, tomography) allowed the detection of earlier ectatic disease, before visual loss and subjective complaints. The Belin ABCD classification/staging system was introduced on a Scheimpflug imaging system [Pentacam, (Oculus GmbH, Wetzlar, Germany)] to address previous shortcomings. The ABCD system utilizes 4 parameters: Anterior ("A") and posterior ("B" for Back) radius of curvature taken from a 3.0 mm optical zone centered on the thinnest point, "C" is minimal Corneal thickness, and "D" best spectacle Distance visual acuity. The first 3 parameters (A, B, C) are machine-generated objective measurements that can be used to determine progressive change.The staging system is not limited to a specific commercial entity and can be incorporated in any tomographic imaging system. The ABCD Progression Display graphically displays each parameter and shows when statistical change above measurement noise is reached. This should allow the clinician the ability to diagnose progressive disease at a much earlier stage than was previously possible, with the confidence that earlier intervention could prevent visual loss.

Purpose: To investigate the changes in corneal backward scattering using Scheimpflug tomography (densitometry) 6 months after intrastromal corneal ring segments (Keraring) implant for keratoconus and to correlate with clinical results., Methods: Along with standard ophthalmic examination, Scheimpflug tomography using Pentacam HR was performed to document corneal densitometry and corneal shape. A densitometry map was displayed using grayscale units (GSUs) ranging from 0 to 100 (minimum to maximum light scattering) in 4 concentric annuluses: central 2-, 2- to 6-, 6- to 10-, 10- to 12-, and total 12-mm corneal diameter and at 3 different depths: anterior 120 μm, posterior 60 μm, middle (varying accordingly to the total thickness), and total thickness., Results: The changes in mean corneal densitometry values for anterior, central, and posterior layers were 3.82 ± 3.13, 2.70 ± 1.78, and 1.68 ± 1.52 GSU, respectively, and for annuluses of 0 to 2, 2 to 6, 6 to 10, and 10 to 12 mm were 2.96 ± 2.60, 4.53 ± 2.28, 2.09 ± 1.74, and 0.45 ± 3.93 GSU, respectively. The mean values increased for all corneal layers (P < 0.05), except in the peripheral 10- to 12-mm annulus (P> 0.05). The highest increase was in the annulus 2 to 6 mm of the anterior layer (5.72 ± 3.70 GSU). Changes in the mean densitometry showed a significant correlation with the mean of average keratometry changes only for the front corneal surface and changes in the Q-values for both corneal surfaces in the 2- to 6-mm annulus for all layers., Conclusions: Significant increase in the corneal densitometry mainly in the anterior 2- to 6-mm annulus of the cornea is associated with the position of the ring segment implant. More studies are needed to elucidate the relevance of such findings.

The approach to corneal ectatic disease has changed dramatically over the last decade with advances in both diagnosis and treatment. Newer treatments, such as corneal cross-linking, have the potential to slow or stop the progression of the disease, but benefit from earlier identification of the disease than had previously been possible or required. The continued use of older diagnostic criteria and ambiguous terminology can lead to erroneous study conclusions that may not be applicable to patients with true pathology., Competing Interests: Consultant OCULUS GmbH CMO CXLOphthalmics but received no financial support for any of this work., (Georg Thieme Verlag KG Stuttgart · New York.)

Purpose: To investigate descriptions and inclusion criteria of keratoconus used in randomized trials assessing the efficacy of surgical and nonsurgical interventions., Methods: Systematic review: we searched (Pre-)Medline and the Cochrane Library from inception until December 2018 and checked the reference lists of included articles and reviews. We included randomized trials assessing the efficacy of any kind of keratoconus treatment. No language restrictions were imposed. We assessed articles against the inclusion criteria, extracted relevant data including any kind of keratoconus description, and examined the methodological quality., Results: Searches retrieved 459 nonduplicate records, and we included 57 randomized controlled trials investigating 9 different surgical interventions with the most used primary outcome measure being maximum keratometry. Only 15 (26.3%) described eligibility parameters regarding keratoconus staging/classification, of which 12 studies used the Amsler-Krumeich classification. Eleven studies were published before 1997 (before publication of the Consolidated Standards of Reporting Trials statement), and none of these described the use of a classification. From 1997 onward, 15 of 46 studies (32.6%) described the incorporation of a classification system (P = 0.051). The average methodological quality of included trails was modest., Conclusions: The evidence from randomized trials, even after introduction of the Consolidated Standards of Reporting Trials statement, remains ill-formed regarding a careful definition of keratoconus. This is unfortunate because imprecisions regarding the specification of included patients preclude clinicians to assess applicability, that is, the extent to which they can use inferences drawn from study participants regarding efficacy and adverse events in the care of individual patients.

Purpose: The aim of this study was to determine whether there are significant clinical variations in the Belin/Ambrosio Enhanced Ectasia Display (BAD display) parameters between Chinese and North American eyes and whether any variations are related to differences in corneal diameter., Design: Retrospective observational study., Methods: Files were generated from patients seeking refractive surgical correction. Patients with previous surgery, evidence of corneal ectasia, or scans representing a non-normal cornea were excluded. Unpaired t tests were performed for all variables. Regression analyses were performed for all variables with respect to corneal diameter, and compared to evaluate the influence of corneal diameter between populations. Data were graphed as standard scores (z scores) to compare different parameters., Results: 127 North American and 49 Chinese patients met study criteria. Statistically significant differences existed for corneal diameter (P < 0.01), anterior elevation at the thinnest point (P < 0.01), and Df (P < 0.01). In both populations, statistically significant correlations existed between corneal diameter and most indices, and most profoundly on pachymetric progression and final D. Regression slopes revealed a statistically significant difference for the influence of corneal diameter on ARTmax (P = 0.04) and was nearly significant for final D (P = 0.06)., Conclusions: Corneal diameter had the greatest influence on pachymetric progression and final D, and more profoundly in the Chinese. This suggests that incorporating corneal diameter as an additional variable may make the BAD display more universally applicable. Also, the differences in anterior elevation parameters suggest that specific ethnic/geographic normative values may be beneficial for the BAD display.

Objective: To assess the anatomical changes produced by implantation of the complete intracorneal ring (MyoRing; DIOPTEX, GmbH, Linz, Austria) on the different corneal anatomical layers as measured by the ABCD keratoconus staging system 6 months after operation., Methods: Seventeen eyes of 17 keratoconic patients implanted with MyoRing using the femtosecond laser were assessed preoperatively and postoperatively. Distance uncorrected visual acuity and distance corrected visual acuity (DCVA), refraction, and Scheimpflug tomography with Pentacam HR were determined for each patient. The 4 ABCD parameters were recorded, which include the anterior and posterior radius of curvature from a 3.0-mm optical zone centered on the thinnest point (TP) (A & B, respectively), the thinnest corneal thickness (C), and DCVA (D)., Results: Statistically significant improvement (preoperatively vs. postoperatively) in the DCVA (0.40±0.21 vs. 0.67±0.20 in decimal notation, P=0.001) associated with significant flattening effect was observed in both anterior (6.02±0.40 vs. 7.18±0.54 mm, P<0.001) and posterior (4.49±0.41 vs. 4.66±0.40 mm, P=0.001) radius of curvature. There was no significant change in the corneal thickness at the TP (P=0.981). The largest magnitude of change occurred on the anterior surface as measured by the "A" parameter. The average ABCD keratoconus staging before MyoRing implantation was A4B4C2D2 and changed to A1B4C2D1 6 months after ring implantation., Conclusion: Despite the placement of MyoRings in the posterior one-third of the cornea, the greatest changes in curvature occurred on the anterior corneal surface. The ABCD classification and staging system allows for a differential assessment of the different anatomical layers and may prove useful in better understanding of the geometric (structural) and functional changes after MyoRing implantation, as well as with other corneal procedures.

Purpose: We aim to design two sampling methods, the grid and sectoral methods, to provide more precise detection of focal corneal scar changes with time following pterygium excision with the Pentacam imaging system., Methods: This is a retrospective study of our previous prospective observational case series. Thirty patients underwent primary pterygium excision with adjuvant topical mitomycin-C application were followed up and imaged with Pentacam system at postoperative weeks 1, 4, 12 and month 18. Grid and sectoral methods were used to sample density changes (in grayscale units, GSU) over the scarred areas as well as the clear pole of the same cornea., Results: Using the grid method, the average corneal densities were 39.4, 37.1, 36.7 and 34.7 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. On the other hand, using the sectoral method, the average corneal densities were 35.3, 33.3, 32.5 and 31.9 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. Paired t tests achieved statistical significance when comparing all follow-up time points to first postoperative visit. A statistically significant effect of time on the average density was shown on ANOVA (p < 0.001) using both analyses over the scarred areas, but not over the clear pole of the same cornea (p > 0.05)., Conclusion: Our novel approach to monitor corneal density changes using the grid or sectoral sampling methods seemingly enhances the power in monitoring density changes in corneal scars when compared to conventional total-diameter average densitometry.

Purpose: To improve the detection of corneal ectasia susceptibility using tomographic data., Design: Multicenter case-control study., Methods: Data from patients from 5 different clinics from South America, the United States, and Europe were evaluated. Artificial intelligence (AI) models were generated using Pentacam HR (Oculus, Wetzlar, Germany) parameters to discriminate the preoperative data of 3 groups: stable laser-assisted in situ keratomileusis (LASIK) cases (2980 patients with minimum follow-up of 7 years), ectasia susceptibility (71 eyes of 45 patients that developed post-LASIK ectasia [PLE]), and clinical keratoconus (KC; 182 patients). Model accuracy was independently tested in a different set of stable LASIK cases (298 patients with minimum follow-up of 4 years) and in 188 unoperated patients with very asymmetric ectasia (VAE); these patients presented normal topography (VAE-NT) in 1 eye and clinically diagnosed ectasia in the other (VAE-E). Accuracy was evaluated with ROC curves., Results: The random forest (RF) provided highest accuracy among AI models in this sample with 100% sensitivity for clinical ectasia (KC+VAE-E; cutoff 0.52), being named Pentacam Random Forest Index (PRFI). Considering all cases, the PRFI had an area under the curve (AUC) of 0.992 (94.2% sensitivity, 98.8% specificity; cutoff 0.216), being statistically higher than the Belin/Ambrósio deviation (BAD-D; AUC = 0.960, 87.3% sensitivity, 97.5% specificity; P = .006, DeLong's test). The optimized cutoff of 0.125 provided sensitivity of 85.2% for VAE-NT and 80% for PLE, with 96.6% specificity., Conclusion: The PRFI enhances ectasia diagnosis. Further integrations with corneal biomechanical parameters and with the corneal impact from laser vision correction are needed for assessing ectasia risk., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Purpose: To assess the changes in the ABCD keratoconus staging system 6 months after intracorneal ring segment implantation., Methods: Fifty eyes of 50 patients with keratoconus who were implanted with the Keraring (Mediphacos, Belo Horizonte, Brazil) using the femtosecond laser were assessed. Preoperative and postoperative assessments included determination of distance uncorrected visual acuity and distance corrected visual acuity (DCVA), refraction, and Scheimpflug tomography with the Pentacam HR. In the ABCD keratoconus staging system, the elements A, B, C, and D stand for anterior and posterior radii of curvature in a 3.0-mm zone centered on the thinnest point (TP), corneal thickness at the TP, and DCVA, respectively., Results: Keraring implantation produced significant flattening changes (preoperatively vs. postoperatively) in the anterior (6.60 ± 0.48 vs. 7.22 ± 0.57 mm, P < 0.001) and posterior (4.99 ± 0.47 vs. 5.16 ± 0.53 mm, P = 0.002) radii of curvature of the 3-mm zone centered on the corneal TP associated with a statistically significant improvement in the DCVA (0.56 ± 0.24 vs. 0.70 ± 0.22 in the decimal notation, P = 0.001) with no significant change in the corneal thickness at the TP (P = 0.285). The most changes occurred in element A of the ABCD keratoconus classification. Also, a 1-stage change was observed for element B, whereas elements C and D did not show changes in their postoperative stages after ring implantation. ABCD keratoconus staging before ring implantation was A2B3C2D1 and changed to A1B2C2D1 6 months after surgery., Conclusions: The ABCD staging system provides a more comprehensive guide that better illustrates the structural changes and visual acuity as one aspect of visual function after the implantation of the intrastromal corneal ring segments.

The initial published clinical report on riboflavin/ultraviolet A corneal cross-linking (CXL) for treatment of progressive keratoconus dates back to 2003. CXL has since then been widely used outside the United States for treatment of progressive keratoconus and post-laser in situ keratomileusis ectasia. The Food and Drug Administration (FDA) approved Avedro Inc.'s corneal cross-linking system (KXL) for treatment of patients with progressive keratoconus and post-laser in situ keratomileusis ectasia in April 2016. The procedure is not currently approved for stable keratoconus. There are 2 FDA-approved topical ophthalmic solutions for use in CXL. Riboflavin 5'-phosphate in 20% dextran ophthalmic solution 0.146% (Photrexa Viscous) and Riboflavin 5'-phosphate ophthalmic solution 0.146% (Photrexa) are intended for use with the KXL system. Photrexa Viscous is used in all CXL procedures, whereas Photrexa is indicated for use when the corneal stroma is thinner than 400 µm after completion of the Photrexa Viscous induction period. The FDA-approved procedure using the Dresden protocol (UV-A, 3 mW/cm for 30 min) induces cytologic and morphologic changes in the anterior 250 to 300 µm of the corneal stroma. It has been believed that a minimum thickness of 400 μm was necessary to protect the corneal endothelium from potential damage. The CXL procedure using the standard Dresden protocol is established as the gold standard for treatment of progressive keratoconus. CXL treatment is indicated for a list of conditions ranging from corneal ectasia to infectious keratitis. Newer protocols, treatment regimens, and expanded indications will require further refinements, investigations, and long-term studies.

This review describes the evolution of the diagnosis and treatment of keratoconus from the earliest written description to present day. The first description was provided in 1736 by Benedict Duddell who described the prominent corneas of a fourteen-year-old boy. Throughout the 19th century, a variety of surgical procedures were proposed to manage the disease, such as surgically repositioning the pupil away from the cone, iris incarceration to produce a slit-like pupil, cauterization of the cone to produce a scar, and full thickness elliptical excision of the cone. Despite the ingenuity of these procedures, many led to serious complications. In 1936, Ramon Castroviejo revolutionized surgical management by performing the first corneal transplant for keratoconus. The advent of refractive surgery in the 1990s brought about a sudden and critical need for better understanding of keratoconus and corneal ectatic disease. Topographic analysis allowed for earlier detection of keratoconus, prior to clinical signs and symptoms. Tomographic analysis provided analysis of the anterior and posterior surfaces of the cornea and allowed for even earlier detection. The Belin/Ambrosio Enhanced Ectasia Display on the Pentacam incorporates anterior and posterior elevation, pachymetric map, best fit sphere and enhanced reference surface to provide an overall "D" value that is predictive of ectatic disease. This display allows refractive providers to quickly and accurately screen potential refractive surgery candidates to identify those at risk for ectasia and early subclinical keratoconus. Corneal crosslinking was revolutionary in the treatment of keratoconus. There have been several randomized controlled trials that have found it to be safe and effective to halt ectatic progression. Crosslinking was recently approved by the FDA for progressive keratoconus. Currently, there is no clear definition of ectasia progression. Providers must be able to clearly, objectively and consistently diagnose progressive disease to institute timely treatment in the population with the greatest potential benefit. The new Belin ABCD grading system and progression analysis incorporated into the Oculus Pentacam software provides an objective way of assessing progression over time. Keratoconus diagnosis and management have grown tremendously since the first description in 1736, but there is still much to learn about keratoconus and its management., Competing Interests: Dr. Belin is a consultant to OCULUS GmbH, Avedro, & CXLO, but received no support for this study. The other authors have no conflict of interest to disclose, no financial or proprietary interest in any material or method mentioned in this manuscript. None of the authors received no financial incentive for the data presented. The authors have no public or private support., (Georg Thieme Verlag KG Stuttgart · New York.)

Objective: To investigate the visual and anatomical outcomes of Boston keratoprosthesis (Kpro) type 1 reimplantation., Design: Subgroup analysis of multicentre prospective cohort study., Participants: Of 303 eyes that underwent Kpro implantation between January 2003 and July 2008 by 1 of 19 surgeons at 18 medical centres, 13 eyes of 13 patients who underwent reimplantation of Boston Kpro type 1 were compared with 13 eyes of 13 diagnosis-matched patients who underwent initial implantation., Methods: Forms reporting preoperative, intraoperative, and postoperative parameters were prospectively collected and analyzed. Main outcome measures were Kpro retention and logMAR visual acuity., Results: After a mean follow-up time of 17.1 ± 17.6 months, the retention of both initial and repeat Kpro implantation was 92.3% (12/13 in both groups), and 62% of initial implantation and 58% of repeat implantation eyes achieved visual acuity better than 20/200. Vision worse than 20/200 was often due to glaucoma or posterior segment pathology. Best-recorded logMAR visual acuity was significantly improved postoperatively in both groups (p < 0.001), and there was no statistically significant difference in final logMAR visual acuity between the 2 groups (p = 0.89). Sterile keratolysis (n = 4) and fungal infection (n = 5) were the most common causes of initial Kpro failure in the repeat Kpro group. The single failure in the repeat Kpro implantation group was due to fungal keratitis, and in the control group it was related to Kpro extrusion., Conclusions: Repeat Kpro implantation is a viable option after failed initial Kpro, with visual and anatomical outcomes comparable to those of initial procedures., (Copyright © 2018 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.)

Purpose: To report 5 cases of advanced unilateral keratoconus documented by sequential tomographic evaluation., Methods: Retrospective review over a 10-year period at a single practice identifying patients with unilateral keratoconus by advanced imaging throughout the follow-up period., Results: Five patients were identified with progressive keratoconus in 1 eye and no changes in the fellow eye based on full tomographic evaluation and analysis of both anterior and posterior corneal surfaces and corneal thickness with a mean follow-up period of 59 months (range 39-86)., Conclusions: Keratoconus is believed to be a bilateral disease that can present asymmetrically. We present 5 cases that appear to be true unilateral keratoconus with no associated mechanical environmental factors.

Purpose: To evaluate long-term changes in mean keratometry, astigmatism, true net power (TNP), and total corneal refractive power (TCRP) of corneas after primary pterygium excision., Methods: This is a prospective observational series conducted at a tertiary teaching hospital eye center in Hong Kong. A total of 31 eyes of 31 patients with primary pterygium excision were included. Patients with recurrent or double-headed pterygia or a history of corneal scars from previous trauma, infection, or surgery were excluded. Data were collected prospectively at postoperative weeks 1, 4, 12, and month 18., Results: Mean keratometry of the anterior cornea was 44.3 diopters (D) [95% confidence interval (CI): 43.6-44.9 D] at week 1, 44.3 D (95% CI: 43.6-44.9 D, standard error = 0.3) at week 4, 44.3 D (95% CI: 43.7-44.9 D) at week 12, and 44.1 D (95% CI: 43.5-44.7 D) at month 18. Mean astigmatism of the anterior cornea was 1.1 D (95% CI: 0.7-1.4 D), 1.0 D (95% CI: 0.7-1.3 D), 0.9 D (95% CI: 0.6-1.1 D), and 1.0 D (95% CI: 0.7-1.3 D) at postoperative 1, 4, 12 weeks, and 18 months, respectively. Mean keratometry, astigmatism of the anterior and posterior cornea, TNP and TCRP at 2.0-mm, 3.0-mm, 4.0-mm rings and zones remained unchanged on all follow-up visits (P = 1 for all comparisons)., Conclusions: Keratometric values including TNP and TCRP were stable as soon as 1 week after pterygium excision. This information might help clinicians in planning subsequent intraocular surgery that requires biometric assessment for intraocular lens implantation.

The aim of the present study was to investigate the efficacy of a novel surgical intervention, excisional keratectomy combined with focal cryotherapy and amniotic membrane inlay (EKCAI), for the treatment of recalcitrant filamentary fungal keratitis. A retrospective analysis was performed of patients who underwent excisional keratectomy combined with conjunctival flap inlay (EKCFI), EKCAI or therapeutic penetrating keratoplasty (TPK) from January 2006 to January 2011. Recalcitrance was determined as being unresponsive to standard medical antifungal therapy for at ≥1 week. Outcome measures among the three intervention modalities were compared. A total of 128 patients had a follow-up of ≥1 year after the primary intervention. The success rates of interventions at 1-year follow-up were 58.33% in the EKCFI group, 88.37% in the EKCAI group and 93.44% in the TPK group (P<0.0002). The preoperative visual acuity of the three groups were similar (P=0.6458), while the postoperative best-corrected visual acuity (BCVA) of patients without recurrence was significantly different among the three groups 3 months after surgery. The best postoperative BCVA was found in the TPK group, while the worst was in the EKCFI group. In conclusion, EKCAI does not require donor cornea, is straightforward surgically, and has a favorable success rate compared with EKCFI.

Purpose: To evaluate the long-term change in average corneal densities at 18 months after primary pterygium excision with topical adjuvant mitomycin-C application, particularly the relationship between anterior and posterior corneal layer densities., Methods: Prospective observational case series. Patients were imaged with the Pentacam at 18 months after their surgery. Average corneal densities were the primary outcome and were compared with postoperative weeks 1, 4, and 12 data using paired t test., Results: In all, 31 eyes of 31 patients were recruited. Mean age at time of operation was 62.0 ± 9.4 years. Mean best-corrected logarithm of the minimal angle of resolution visual acuity at 18 months was 0.14. The mean total anterior, central, and posterior average corneal densities were 30.6, 25.9, and 20.5 respectively. Compared with postoperative week 1 data, the anterior layer was reduced by 12.7% (P = 0.0144); however, there was no significant change in the central and posterior layers (P = 0.5353 and 0.0858, respectively). Subgroup analyses did not support the use of a 10- to 12-mm annulus as opposed to total-diameter data, and density reduction effect at 18 months from week 12 and week 1 seemed to be stronger in males (P = 0.0074 and 0.0042, respectively)., Conclusions: Anterior corneal scars continued to diminish in density with time. Previous finding of a significant increase in posterior layer density at postoperative week 12 is likely not a result of optical phenomenon caused by a less dense anterior layer. Sex difference in terms of scar remodeling may be present.

Purpose: To propose a new keratoconus classification/staging system that utilises current tomographic data and better reflects the anatomical and functional changes seen in keratoconus., Method: A previously published normative database was reanalysed to generate both anterior and posterior average radii of curvature (ARC and PRC) taken from a 3.0 mm optical zone centred on the thinnest point of the cornea. Mean and standard deviations were recorded and anterior data were compared to the existing Amsler-Krumeich (AK) Classification. ARC, PRC, thinnest pachymetry and distance visual acuity were then used to construct a keratoconus classification., Results: 672 eyes of 336 patients were analysed. Anterior and posterior values were 7.65 ± 0.236 mm and 6.26 ± 0.214 mm, respectively, and thinnest pachymetry values were 534.2 ± 30.36 µm. The ARC values were 2.63, 5.47 and 6.44 standard deviations from the mean values of stages 1-3 in the AK classification, respectively. PRC staging uses the same standard deviation gates. The pachymetric values differed by 4.42 and 7.72 standard deviations for stages 2 and 3, respectively., Conclusion: A new keratoconus staging incorporates anterior and posterior curvature, thinnest pachymetric values, and distance visual acuity and consists of stages 0-4 (5 stages). The proposed system closely matches the existing AK classification stages 1-4 on anterior curvature. As it incorporates posterior curvature and thickness measurements based on the thinnest point, rather than apical measurements, the new staging system better reflects the anatomical changes seen in keratoconus., (Georg Thieme Verlag KG Stuttgart · New York.)

Pentacam is a rotating Scheimpflug-based corneal and anterior segment tomographer that gives as comprehensive analysis of corneal 3D geometry. With this device the detection of mild keratoconus or ectasia susceptibility is possible. This is fundamental for screening ectasia risk prior to laser vision correction. The identification of susceptible cases at risk for developing progressive iatrogenic ectasia should go beyond (but not over) corneal front surface topography., (Copyright © 2015. Published by Elsevier GmbH.)

Purpose: To establish a normative database for corneal elevation in Chinese myopic patients who underwent refractive surgery, and analyze the association of corneal elevation with sex, age, and ocular parameters., Methods: A total of 3000 eyes in 1500 patients were evaluated with the Pentacam. Anterior and posterior elevations were measured at the apex and thinnest point. Normative thresholds were defined according to the Tukey method. Univariate and multivariate analyses were performed to assess the association of corneal elevation with sex, age, and ocular parameters., Results: Normal upper limits for corneal elevation in adult Chinese were 4.95μm, 5.25μm, 6.2μm, and 11.0μm at the anterior apex, anterior thinnest point, posterior apex, and posterior thinnest point, respectively. Thinner corneal pachymetry at the apex and greater anterior corneal astigmatism tended to show greater anterior corneal elevation values. Younger age, greater anterior corneal astigmatism, lower anterior and posterior keratometry, and shallower anterior chamber depth resulted in greater posterior corneal elevation values., Conclusions: Locally derived thresholds may offer higher sensitivity and specificity when screening eyes for myopic refractive surgery, and keratoconic and post-orthokeratology eyes. Anterior and posterior corneal elevation at the apex and thinnest point were associated significantly with anterior corneal astigmatism, showing a positive correlation., (Copyright © 2016 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.)

Several methods have been described in the literature to both evaluate and document progression in keratoconus, but there is no consistent or clear definition of ectasia progression. The authors describe how modern corneal tomography, including both anterior and posterior elevation and pachymetric data can be used to screen for ectatic progression, and how software programs such as the Enhanced Reference Surface and the Belin-Ambrosio Enhanced Ectasia Display (BAD) can be employed to detect earlier changes. Additionally, in order to describe specific quantitative values that can be used as progression determinants, the normal noise measurement of the three parameters (corneal thickness at the thinnest point, anterior and posterior radius of curvature (ARC, PRC) taken from the 3.0 mm optical zone centered on the thinnest point), was assessed. These values were obtained by imaging five normal patients using three different technicians on three separate days. The 95 % and 80 % one-sided confidence intervals for all three parameters were surprisingly small (7.88/4.03 μm for corneal thickness, 0.024/0.012 mm for ARC, and 0.083/0.042 mm for PRC), suggesting that they may perform well as progression determinants.

Purpose: To report logarithm of the minimal angle of resolution (logMAR) visual outcomes of the Boston keratoprosthesis type 1., Design: Prospective cohort study., Methods: Preoperative, intraoperative, and postoperative parameters of 300 eyes of 300 patients who underwent implantation of a Boston keratoprosthesis type 1 device between January 2003 and July 2008 by 1 of 19 surgeons at 18 medical centers were collected., Results: After an average of 17.1 ± 14.8 months, visual acuity improved significantly (P < .0001) to a mean final value of 0.89 ± 0.64 (20/150). There were also significantly fewer eyes with light perception (6.7%; n = 19; P < .0001), although 3.1% (n = 9) progressed to no light perception. There was no association between age (P = .08), sex (P = .959), operative side (P = .167), or failure (P = .494) and final visual acuity. The median time to achieve 20/200 visual acuity was 1 month (95% confidence interval 1.0-6.0) and it was retained for an average of 47.8 months. Multivariate analysis, controlling for preoperative visual acuity, demonstrated 2 factors associated with final visual outcome: chemical injury was associated with better final vision (P = .007), whereas age-related macular degeneration was associated with poorer vision (P < .0001)., Conclusions: The Boston keratoprosthesis type 1 is an effective device for rehabilitation in advanced ocular surface disease, resulting in a significant improvement in visual acuity. Eyes achieved a mean value of 20/150 (0.89 ± 0.64 logMAR units) after 6 months and this was relatively stable thereafter. The best visual prognosis is observed in chemical injury eyes, whereas the worst prognosis is in aniridia, although the latter has limited visual potential., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Purpose: To propose a series of standardized guidelines for reporting keratoprosthesis (KPRO) results., Methods: At the most recent KPRO Study Group Meeting (Barcelona, 2015), representatives of the 4 multinational corneal societies (Cornea Society, Asia Cornea Society, EuCornea, and PanCornea) and the KPRO Study Group agreed to propose consistent terminology for reporting KPRO results, especially in describing the length of follow-up and in the description of the KPRO itself. Consensus was reached for minimal reporting guidelines., Results: The 4 multinational corneal societies and the KPRO Study Group agreed to standardized terminology for reporting the length of follow-up, preoperative diagnosis grouping, and data stratification based on the KPRO type used., Conclusions: Guidelines suggesting minimal reporting standards will assist in both data collection and reporting and will allow for better comparative analysis and pooling of the available data.