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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. [ABSTRACT FROM AUTHOR]

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 CH2 (2925 cm−1) and CH3 (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. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of tafluprost on the central corneal thickness (CCT) in patients with primary open-angle glaucoma (POAG). Methods: This was a prospective study and included 100 eyes of 54 patients with POAG. All patients received tafluprost 0.0015% (Saflutan®) once daily in one or both eyes. CCT was measured by using noncontact pachymetry prior to the treatment and after 6 and 12 months. Results: Mean CCT of all treated eyes ( n = 100) was 547.79 ± 29.48 μm at baseline, 535.61 ± 26.54 μm after 6 months and 533.55 ± 26.45 μm after 12 months (Student's t test, p < 0.0001). Ninety-three percent of all treated eyes showed a decrease of CCT. CCT reduction was more significant within the first six months of the treatment period (Student's t test, p < 0.0001). After 12 months, a CCT reduction >25 μm occurred in 5% of all treated eyes. There was a significant positive correlation between the magnitude of corneal thinning and the initial CCT (Pearson, r = 0.49, p < 0.0001) but not between the magnitude of corneal thinning and intraocular pressure (IOP) reduction (Pearson, r = 0.145, p = 0.15). Discussion: Long-term use of tafluprost may decrease the CCT in patients with POAG. Consequently, clinicians must be aware of prolongated CCT variations that may arise throughout the follow-up period for proper IOP targeting and management. [ABSTRACT FROM AUTHOR]

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]

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. [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]

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. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. [Copyright &y& Elsevier]