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Purpose: The aim was to assess the repeatability of Fourier transfom analysis of videokeratographic data using Pentacam in normal (CG), keratoconic (KC) and post-CXL (CXL) corneas., Methods: This was a prospective, clinic-based, observational study. One randomly selected eye from all study participants was included in the analysis: 62 normal eyes (CG group), 33 keratoconus eyes (KC group), while 34 eyes, which had already received CXL treatment, formed the CXL group. Fourier analysis of keratometric data were obtained using Pentacam, by two different operators within each of two sessions. Precision, repeatability and Intraclass Correlation Coefficient (ICC), were calculated for evaluating intrassesion and intersession repeatability for the following parameters: Spherical Component (SphRmin, SphEcc), Maximum Decentration (Max Dec), Regular Astigmatism, and Irregularitiy (Irr). Bland-Altman analysis was used for assessing interobserver repeatability., Results: All parameters were presented to be repeatable, reliable and reproductible in all groups. Best intrasession and intersession repeatability and reliability were detected for parameters SphRmin, SphEcc and Max Dec parameters for both operators using ICC (intrasession: ICC > 98%, intersession: ICC > 94.7%) and within subject standard deviation. Best precision and lowest range of agreement was found for the SphRmin parameter (CG: 0.05, KC: 0.16, and CXL: 0.2) in all groups, while the lowest repeatability, reliability and reproducibility was detected for the Irr parameter., Conclusions: The Pentacam system provides accurate measurements of Fourier tranform keratometric data. A single Pentacam scan will be sufficient for most clinical applications.

Purpose: To develop an algorithm for the Fourier analysis of posterior corneal videokeratographic data and to evaluate the derived parameters in the diagnosis of Subclinical Keratoconus (SKC) and Keratoconus (KC)., Methods: This was a cross-sectional, observational study that took place in the Eye Institute of Thrace, Democritus University, Greece. Eighty eyes formed the KC group, 55 eyes formed the SKC group while 50 normal eyes populated the control group. A self-developed algorithm in visual basic for Microsoft Excel performed a Fourier series harmonic analysis for the posterior corneal sagittal curvature data. The algorithm decomposed the obtained curvatures into a spherical component, regular astigmatism, asymmetry and higher order irregularities for averaged central 4 mm and for each individual ring separately (1, 2, 3 and 4 mm). The obtained values were evaluated for their diagnostic capacity using receiver operating curves (ROC). Logistic regression was attempted for the identification of a combined diagnostic model., Results: Significant differences were detected in regular astigmatism, asymmetry and higher order irregularities among groups. For the SKC group, the parameters with high diagnostic ability (AUC > 90%) were the higher order irregularities, the asymmetry and the regular astigmatism, mainly in the corneal periphery. Higher predictive accuracy was identified using diagnostic models that combined the asymmetry, regular astigmatism and higher order irregularities in averaged 3and 4 mm area (AUC: 98.4%, Sensitivity: 91.7% and Specificity:100%)., Conclusions: Fourier decomposition of posterior Keratometric data provides parameters with high accuracy in differentiating SKC from normal corneas and should be included in the prompt diagnosis of KC., (© 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists.)

Purpose: To evaluate the contribution of Fourier analysis of videokeratographic data in the diagnosis of subclinical keratoconus and keratoconus., Setting: Eye Institute of Thrace, Democritus University, Alexandroupolis, Greece., Design: Observational case series., Methods: The following Pentacam-derived parameters, resulting from Fourier decomposition of keratometric data, were evaluated for their diagnostic capacity using receiver operating curves: spherical component and eccentricity, maximum decentration, regular astigmatism in the center and in the periphery, mean astigmatism, irregularities, regular astigmatism in the center plus the irregularities, and total astigmatism. Logistic regression was performed to identify a combined diagnostic model., Results: The study comprised 80 keratoconus eyes, 55 eyes diagnosed with subclinical keratoconus, and 50 normal eyes. Significant differences were detected in spherical eccentricity, maximum decentration, irregularities, regular astigmatism in the center and in the periphery, regular astigmatism in the center plus the irregularities, mean astigmatism, and total astigmatism parameters between the groups. Almost all parameters had high diagnostic ability in both study groups (area under the curve >90%). Among individual parameters, those with the highest predictive accuracy were the regular astigmatism in the center plus the irregularities (subclinical keratoconus 97.6%, keratoconus 98.8%) and the maximum decentration (subclinical keratoconus 91.4%, keratoconus 98.5%). Sufficient predictive accuracy (subclinical keratoconus 99.4, keratoconus 100%) was identified in a diagnostic model that combined the regular astigmatism in the center plus the irregularities and the maximum decentration., Conclusion: Fourier decomposition of keratometric data provided parameters with high accuracy in differentiating corneas with subclinical keratoconus from normal corneas and should be included to allow prompt diagnosis of keratoconus., Financial Disclosure: None of the authors has a financial or proprietary interest in any material or method mentioned., (Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the reproducibility of different Scheimpflug imaging-derived reference bodies in normal, keratoconus (KC), and crosslinked (CXL) eyes., Methods: In this prospective, observational study, 40 participants populated the control group (CG), while 33 and 34 patients formed the KC group and the CXL group, respectively. One eye was randomly selected when both were eligible. Elevation measurements were obtained using Scheimpflug camera, by applying the following reference bodies: the best fit sphere (BFS), the best fit toric ellipsoid (BFTE), the best fit toric ellipsoid with fixed eccentricity of 0.4 (BFTEF), the best fit ellipsoid (BFE), and the best fit torus, by 2 operators in 2 sessions. The variability of different reference bodies' parameters was assessed using intraclass correlation coefficient (ICC)., Results: Differences between operators were nonsignificant for all reference bodies' parameters in all study groups (p>0.1). Regarding CG, BFS for both operators and BFTE for operator 1 presented the best intrasession repeatability (majority of ICCs >0.90), while average interobserver reliability was recorded for the majority of reference bodies' parameters. Regarding KC and CXL groups, BFS, BFTEF, and BFE reference bodies demonstrated the best intrasession and interobserver reproducibility (majority of ICCs >0.90) for both groups. Steep and flat radius parameters presented the best overall reproducibility, with the majority of ICCs for all reference bodies ranging above 0.90, in all study groups., Conclusions: High variability was encountered for most reference surfaces. Ellipsotoric surfaces presented acceptable repeatability in KC and post-CXL corneas.

Purpose: To assess the potential impact of corneal crosslinking treatment (365 nm ultraviolet (UV)A irradiation with riboflavin) on the material properties of Intracorneal Rings Segments (ICRS)., Materials and Methods: Material properties were studied using FT-IR spectroscopy and UV-Vis spectroscopy. Rings were examined: (1) after installation of riboflavin solution, (2) after irradiation with UV-A light and (3) after instillation of riboflavin solution followed by instillation and coeval irradiation. The experiments followed the standard corneal cross-linking (CXL) protocol of corneal crosslinking treatment., Results: After instillation of riboflavin solution, a permanent intense yellow staining of the samples was observed. UV-Vis spectroscopy confirmed that a certain amount of riboflavin solution was absorbed into the samples after CXL procedure. FT-IR spectroscopic analysis showed alterations in the spectra of ICRS mainly at the 2800-3200 cm(-1) spectral region [modification in band intensities of CH(2) (2925 cm(-1)) and CH(3) (2950 cm(-1))]., Conclusions: Our results suggest crosslinking reaction in ICRS material. This should be taken into consideration prior to any CXL treatment of post ICRS-implanted cornea.

Purpose: To evaluate the diagnostic capacity of the Ocular Response Analyzer's keratoconus match index (KMI) and keratoconus match probability (KMP) classification in keratoconus-suspect eyes., Setting: Department of Ophthalmology, University Clinics Saarland, Homburg, Germany., Design: Comparative case series., Methods: The KMI and KMP parameters in keratoconus-suspect eyes and normal eyes (control group) were compared. The quantitative keratoconus percentage index was calculated for all suspect eyes. According to the thinnest corneal thickness (TCT), keratoconus-suspect eyes were divided into 2 subgroups: subgroup 1 (TCT <520 μm) and subgroup 2 (TCT >520 μm). The KMI's overall predictive accuracy was assessed using receiver operating characteristic (ROC) curves. The relationship between KMI and a series of Scheimpflug-derived keratoconus-related indices was evaluated using Spearman analysis., Results: The mean KMI was 0.41 ± 0.29 (SD) in the keratoconus-suspect group (50 eyes) and 0.94 ± 0.29 in the control group (50 eyes) (P<.001). Nonsignificant KMI differences were detected between the keratoconus-suspect subgroups (subgroup 1, 27 eyes; subgroup 2, 23 eyes) (P=.059). Nonsignificant correlations were found between Scheimpflug indices and the KMI. The KMP identified 27.65% of control eyes as keratoconus suspect and 10.71%, 28.57%, and 3.57% of keratoconus-suspect eyes as being normal, having mild keratoconus, or having moderate keratoconus, respectively. The ROC analysis for the KMI indicated a predictive accuracy of 94% (cutoff point 0.72)., Conclusions: The KMI seems to be a valuable index in the early diagnosis of keratoconus-suspect eyes. The KMP identified a significant percentage of topographically defined keratoconus-suspect eyes as normal or keratoconic., Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned., (Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the contribution of reference bodies for elevation maps in diagnosis of keratoconus (KC) and forme fruste keratoconus (FFK)., Methods: Study groups included (1) 80 eyes with KC, (2) 55 eyes with FFK, and (3) 95 eyes as control eyes. The maximum elevation value at the central 5 mm of the posterior cornea (MEL) and the elevation value at thinnest corneal point (TEL) were evaluated for their diagnostic capacity using receiver operating characteristic curves under the following reference bodies: sphere, ellipsoid, toric ellipsoid, and torus, with autodiameter and fixed 8-mm-diameter settings. Moreover, characteristic parameters for each reference body and the root mean square (RMS) were evaluated for their diagnostic capacity., Results: Significant differences were detected in TEL, MEL, and RMS parameters among groups, for almost all reference bodies. The highest predictive accuracy (KC group, >99.97%; FFK group, >90.9%) was estimated for the TEL and MEL parameters using the toric ellipsoid (8 mm) reference body with a fixed eccentricity of 0.4. Moreover, the RMS parameter demonstrated sufficient diagnostic capacity (KC group, 99.95%; FFK group, 85.1%). The cutoff points for the TEL parameter were found to be 7 and 3 μm in the KC group and the FFK group, respectively; for the MEL parameter, they were 11 and 6 μm, respectively; and for the RMS parameter, they were 6.87 and 7.19 μm, respectively., Conclusions: The posterior corneal elevation values and the RMS parameter can effectively discriminate KC from normal corneas, although measured values and cutoff points depend on the selection of reference body. Moreover, the use of a toric ellipsoid reference body, with a fixed eccentricity of 0.4, seems to be an effective tool even in diagnosis of FFK.

Background: The aim was to assess the intra-session, inter-session and inter-observer repeatability of curvature and aberrometric measurements of Pentacam-derived posterior corneal surface in normal control (CG), keratoconic (KCG) and after corneal collagen cross-linked (CXLG) groups., Methods: This was a prospective, clinic-based, observational study that was conducted at the Eye Institute of Thrace (EIT) in Alexandroupolis, Greece. Sixty-two normal eyes formed the control group, 33 were in the keratoconic group, while 34 eyes, which already had received corneal collagen cross-linking formed the CXLG. Curvature and aberrometric measurements were obtained using the Pentacam by two operators within each of the two sessions. Precision (Pre), repeatability (COR) and the intra-class correlation coefficient (ICC) were calculated for evaluating intra-session and inter-session repeatability. Bland-Altman analysis was used for assessing inter-observer repeatability., Results: Simulated keratometric parameters K1 and K2, asphericity at the central 8 mm zone (Q8) and central steepest radius of best fit toric ellipsoid reference body (Rs), achieved an acceptable level of accuracy. Aberrometric parameters were repeatable, reliable and reproducible only in terms of the root mean square (RMS) errors (coma, coma-like and the RMS of higher order aberrations or HOA RMS). For both observers, best precision and lowest range of agreement (ROA) was found for HOA RMS parameters in all groups (less than 0.27 and less than 0.29 for the control group, less than 0.95 and less than 0.72 for the keratoconic group and less than 0.67 and 0.53 for the collagen cross-linked group)., Conclusion: The Pentacam system provides precise measurements of corneal posterior keratometry, reference body radius and asphericity for large diameter analysis. Although Zernike coefficients for individuals presented poor repeatability, the coma, coma-like and HOA RMS seem to be accurate indices in characterisation of back corneal aberrations., (© 2013 The Authors. Clinical and Experimental Optometry © 2013 Optometrists Association Australia.)

Purpose: To evaluate the diagnostic capacity of the Ocular Response Analyser's keratoconus match index (KMI) and keratoconus match probability (KMP) classification in a sample of keratoconus (KC) patients., Methods: Keratoconus match index and KMP from 114 KC eyes, randomly selected from 114 patients with bilateral keratoconus (KCG), were compared with the corresponding ones from 109 normal eyes (CG). Keratoconus match index's predictive accuracy was assessed by receiver operating curves (ROC). Keratoconus match probability level of agreement was evaluated at the different KC stages of the Amsler-Krumeich classification. Correlations were estimated with topographic keratoconus classification (TKC), keratoconus index (KI), index of surface variance (ISV), vertical asymmetry (IVA), height asymmetry (IHA), height decentration (IHD), minimal radius (Rmin), central corneal thickness (CCT), thinnest corneal thickness (TCT) mean keratometry (Km) and intraocular pressure (IOPg)., Results: Mean KMI in KCG and CG was 0.20 ± 0.38 and 0.98 ± 0.25, respectively (p < 0.01). Significant KMI differences (p < 0.01) were detected in different KC groups [range: 0.62 ± 0.38 (KC 1), -0.62 ± 0.04 (KC 4)]. Significant correlation was detected between KC staging and KMI (r = -0.56, p < 0.0001). Keratoconus match probability identified 22.03% of the CG eyes as suspect. Moreover, KMP identified 7.01% and 23.68% of the KCG eyes as normal and suspect, respectively. Receiver operating curves analysis for KMI parameter indicated a predictive accuracy of 97.7% (cut-off point: 0.512, sensitivity: 91.18%, specificity: 94.34%)., Conclusions: Keratoconus match index seems to be a reliable index in keratoconus diagnosis and staging. Keratoconus match probability identifies a significant percentage of topographically defined KC and CG eyes as suspect. Diagnostic capacity of these novel indexes needs to be further explored., (© 2013 The Authors. Acta Ophthalmologica © 2013 Acta Ophthalmologica Scandinavica Foundation.)

Purpose: To evaluate the sensitivity and specificity of corneal biomechanical metrics, anterior segment data, and a combination model in differentiating forme fruste keratoconus (FFK) from normal corneas., Methods: A total of 50 FFK eyes were identified by calculation of the KISA index and recruited FFK group. Results were compared with 50 normal eyes (NG group) randomly selected from 50 patients. The following parameters were evaluated for their diagnostic capacity by evaluation of their receiver operating characteristic curves (ROC): corneal hysteresis (CH), corneal resistance factor (CRF), corneal astigmatism (Cyl), anterior chamber depth (ACD), corneal volume (CV) at 3 mm (CV3) and at 5 mm (CV5), maximum posterior elevation value (PEL), central corneal thickness (CCT), thinnest corneal thickness (TCT) and its coordinates (TCTx, TCTy ), the ratio TCT/CCT, pachymetric progression indexes (PPImin, PPIavg, and PPImax), and Ambrósio's relational thickness (ARTmin, ARTavg, and ARTmax). Logistic regression was attempted for identification of a combined diagnostic model., Results: Significant differences were detected in all studied parameters except the Cyl, ACD, TCTx, and CV. Among individual parameters, the highest predictive accuracy was for ARTavg (area under the curve [AUC] 95.4%, sensitivity 90%, specificity 88.9%) and TCT (AUC 95.3%, sensitivity 90.9%, specificity 89%). Sufficient predictive accuracy (AUC 99.4%, sensitivity 98.8%, specificity 94.6%) was identified in a diagnostic model that combined the CRF, ARTavg, and PEL parameters., Conclusions: None of the individual parameters provide sufficient diagnostic capacity in FFK. However, diagnostic models that combine biomechanical and tomographic data seem to provide high accuracy in differentiating FFK from normal corneas.

Purpose: To determine the variability in Scheimpflug image-derived posterior elevation measurements in eyes with keratoconus or corneal collagen crosslinking (CXL)., Setting: Eye Institute of Thrace, Alexandroupolis, Greece., Design: Prospective observational study., Methods: Two operators in 2 sessions obtained posterior elevation measurements using the Pentacam Scheimpflug system. Variability in measurements was assessed using Bland-Altman analysis and intraclass correlation coefficients (ICCs). Measurements were associated with a series of Scheimpflug-derived keratoconus indices using the Pearson correlation and multivariate linear-regression analysis., Results: Mean interobserver differences for the central elevation point (e1) and the highest elevation point (HEP) in the keratoconus group were -0.9 μm (95% limits of agreement [LoA], 5.7 to -7.5 μm) and 1.7 μm (95% LoA, 26 to -22.6 μm), respectively. In the CXL group, the mean differences were 0.2 μm (95% LoA, 6.0 to -5.5 μm) and -6.1 μm (95% LoA, 16.8 to -29 μm), respectively. The ICC values in the keratoconus group were satisfactory for most elevation points; the ICC values were unsatisfactory for a series of points in the lower corneal hemisphere. The ICC values for points in both hemispheres were unsatisfactory in the CXL group; HEP had adequate reproducibility. The e1 and HEP parameters correlated significantly with most Scheimpflug-derived indices (P<.05) in the keratoconus group but not in the CXL group. Regression analysis indicated that the central keratoconus index was the primary determinant of the variability in keratoconus eyes., Conclusions: Scheimpflug-derived posterior elevation measurements had acceptable reproducibility in keratoconus eyes and post-CXL eyes. Less consistent measurements were obtained in the lower hemisphere., (Copyright © 2012 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.)

Purpose: To assess the effect of stage 1 keratoconus (KC) and of the 2 prevalent KC therapeutic options: (1) corneal collagen cross-linking (CXL) and (2) CXL combined with topography-guided photorefractive keratectomy (t-PRK) on self-reported quality of life (QOL) by means of the 25-item National Eye Institute Visual Function Questionnaire (NEI-VFQ 25)., Methods: Thirty-two patients with bilateral KC stage 1 (KC group) and best-corrected visual acuity of 20/20 in both eyes were prospectively recruited. Of them, 19 KC patients underwent typical CXL treatment (CXL group), whereas 13 underwent CXL combined with t-PRK treatment (tCXL group). Only the eye with the most advanced condition received the treatment. Subjects responded to the NEI-VFQ 25 1 day before the treatment and 1 year postoperatively. Thirty-nine age-matched contact lens users formed the control group. NEI-VFQ 25 subscale and total scores were associated with spherical equivalent, mean keratometry, and a series of Scheimpflug imaging-derived corneal variance indexes by means of the Spearman correlation coefficient and multivariate linear regression analysis., Results: Preoperatively, significant differences were detected between the KC group and the control group in VFQ 25 total and all subscale scores (P < 0.05), except "general health," "color vision," and "peripheral vision" domains. According to the multivariate linear regression analysis, the index of height decentration was the most significant predictor of VFQ 25 total score (b = 0.943; P = 0.016). Postoperatively, significant differences were detected in "mental health" and "dependency" VFQ 25 domains for both the CXL and tCXL groups (P = 0.05). Furthermore, the tCXL group demonstrated significant differences in the "near activities" (P = 0.04), "role limitations" (P = 0.02), and "driving" (P < 0.01) subscale scores., Conclusions: Our results suggest that KC exerts a significant impact on KC patients' QOL, even in its early stages with normal best-spectacle-corrected visual acuity. Moreover, both CXL and CXL combined with t-PRK seem to exert a beneficial impact on self-reported QOL, suggesting that they should be applied as soon as possible.

Background: To evaluate corneal hysteresis (CH) and corneal resistance factor (CRF) in keratoconic (KC) eyes before and after corneal collagen cross-linking (CXL). Furthermore, to determine potential correlations with a series of corneal and demographic factors., Methods: The study consisted of 50 KC eyes that underwent CXL. CH and CRF were measured by the ocular response analyzer (ORA). Correlations were attempted with uncorrected visual acuity (UVA), best spectacle-corrected visual acuity (BSCVA), central corneal thickness (CCT), mean keratometry (Km), astigmatism (Astig.), residual astigmatism, age, and gender. Fifty non-KC eyes served as controls., Results: CH and CRF (mean ± SD) for non-KC eyes were 10.1 ± 1.9 mmHg and 9.7 ± 2.4 mmHg respectively, while for KC eyes preoperatively they were 8.2 ± 1.4 mmHg (p = 0.007) and 7.4 ± 2.3 mmHg (p = 0.01) respectively. Non-significant differences were detected between preoperative and postoperative CH and CRF measurements in KC eyes (p = 0.518 and p = 0.479 respectively). Significant correlations were found between ORA parameters and BSCVA, CCT, Km, Astig. and residual astigmatism., Conclusions: ORA parameters demonstrate significant differences between KC and non-KC eyes. Both CH and CRF present significant correlations with visual acuity and corneal parameters. CXL exerts a non-significant impact on ORA measurements.

Purpose: To evaluate the Goldmann applanation tonometer (GAT), the Pascal dynamic contour tonometer (PDCT), and the ocular response analyzer (ORA) tonometer in measuring intraocular pressure (IOP) in keratoconic eyes before and after riboflavin/ultraviolet A corneal collagen crosslinking (CXL), to assess agreement among devices and to analyze the impact of some ocular parameters on their measurements., Methods: Fifty keratoconic eyes were included. Intraocular pressure was measured with GAT, PDCT, and ORA before and after CXL. Fifty nonkeratoconic eyes served as controls. Device agreements were calculated by Bland-Altman analysis. The effect of some ocular characteristics on IOP measurement differences between tonometers was determined., Results: Between the 2 groups, there were statistically significant differences in all examined parameters. Preoperatively, in both groups a statistically significant difference was found in IOP measurements among devices (p<0.05). Bland-Altman analysis showed a bias among devices. On average, PDCT overread GAT and ORA. The IOP measurement differences were better predicted by corneal resistance factor. Postoperatively, in keratoconus eyes, there was no statistically significant difference in IOP measurements among the 3 tonometers (p>0.05). The IOP readings with all tonometers after treatment were higher than those obtained preoperatively; however, not to a statistically significant level, with the exception of PDCT and ORA readings at the first month postoperatively. Corneal resistance factor measurements have no significant change after CXL., Conclusions: Pascal dynamic contour tonometer could provide more consistent and closer to the true IOP readings than GAT and ORA in healthy eyes with corneal thickness outside the 520-550 µm range, in keratoconus patients and after CXL. Corneal resistance factor was associated significantly with agreement among devices.

Background: To evaluate corneal hysteresis (CH) and corneal resistance factor (CRF) in keratoconic (KC) eyes before and after corneal collagen cross-linking (CXL). Furthermore, to determine potential correlations with a series of corneal and demographic factors. Methods: The study consisted of 50 KC eyes that underwent CXL. CH and CRF were measured by the ocular response analyzer (ORA). Correlations were attempted with uncorrected visual acuity (UVA), best spectacle-corrected visual acuity (BSCVA), central corneal thickness (CCT), mean keratometry (Km), astigmatism (Astig.), residual astigmatism, age, and gender. Fifty non-KC eyes served as controls. Results: CH and CRF (mean ± SD) for non-KC eyes were 10.1 ± 1.9 mmHg and 9.7 ± 2.4 mmHg respectively, while for KC eyes preoperatively they were 8.2 ± 1.4 mmHg ( p = 0.007) and 7.4 ± 2.3 mmHg ( p = 0.01) respectively. Non-significant differences were detected between preoperative and postoperative CH and CRF measurements in KC eyes ( p = 0.518 and p = 0.479 respectively). Significant correlations were found between ORA parameters and BSCVA, CCT, Km, Astig. and residual astigmatism. Conclusions: ORA parameters demonstrate significant differences between KC and non-KC eyes. Both CH and CRF present significant correlations with visual acuity and corneal parameters. CXL exerts a non-significant impact on ORA measurements. [ABSTRACT FROM AUTHOR]

Introduction: Corneal collagen cross-linking is a rather new technique that uses riboflavin and ultraviolet A light for collagen fiber stabilization in keratoconus corneas. Other than reversible side effects, the preliminary results of corneal collagen cross-linking studies suggest that it is a rather safe technique. In this report, we demonstrate a case of corneal melting after corneal collagen cross-linking for keratoconus corneas associated with an acute inflammatory response.Case Presentation: A 23-year-old Caucasian man with keratoconus cornea stage 1 to 2 underwent uneventful corneal collagen cross-linking treatment according to the Dresden protocol. The next day the patient had intense photophobia, watering and redness of the eye, and his visual acuity was limited to counting fingers. Slit lamp biomicroscopy revealed severe corneal haze accompanied by non-specific endothelial precipitates following an acute inflammatory response. Mild inflammation could be detected in the anterior chamber. Moreover, the re-epithelialization process could barely be detected. His corneal state gradually deteriorated, resulting in descemetocele and finally perforation.Conclusion: In this report, we present a case of a patient with corneal melting after standard corneal collagen cross-linking treatment for keratoconus corneas following an acute inflammatory response. Despite modifying postoperative treatment, elaboration of all apparent associated causes by the treating physicians and undergoing extensive laboratory testing, the patient developed descemetocele, which led to perforation. Our report suggests that further research is necessary regarding the safety of corneal collagen cross-linking in keratoconus corneas. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the diagnostic capacity of the keratoconus match index (KMI) and keratoconus match probability (KMP) classification from a dynamic bidirectional applanation device (Ocular Response Analyzer) in eyes with pellucid marginal degeneration (PMD). Setting: Department of Ophthalmology, University Clinics Saarland, Homburg, Germany. Design: Cross-sectional study. Methods: Pellucid marginal degeneration eligibility was confirmed by inferior peripheral thinning, corneal protrusion, and irregular astigmatism. The KMI and KMP parameters in PMD eyes (study group) were compared with those in normal eyes (control group). The KMI's overall predictive accuracy was assessed operating characteristic (ROC) curves. The relationship between KMI and corneal hysteresis (CH), the corneal resistance factor (CRF), and a series of Scheimpflug camera indices was evaluated with Spearman analysis (r). Results: The mean KMI in the study group (40 eyes) and control group (40 eyes) was 0.34 ± 0.43 (SD) and 0.95 ± 0.30, respectively (P<.001). The KMI correlated significantly with the CH, CRF, and most Scheimpflug camera indices. Regression analysis indicated that the index of height decentration (r = −0.877, P<.001) was the primary determinant of the KMI. Moreover, the KMP index identified 50.0%, 29.16%, and 20.83% of PMD eyes as ectatic, suspect for ectasia, and normal, respectively. The ROC curve analysis of the KMI parameter indicated a predictive accuracy of 94.8% (cutoff point 0.626; sensitivity 85.71%; specificity 90.1%). Conclusions: The KMI seems to be a promising diagnostic index for PMD. In contrast, the KMP index identified a significant percentage of topographically defined PMD eyes as normal, limiting its diagnostic value in PMD. Financial Disclosures: No author has a financial or proprietary interest in any material or method mentioned. [ABSTRACT FROM AUTHOR]