Optical coherence tomography-based determination of ischaemia onset - the temporal dynamics of retinal thickness increase in acute central retinal artery occlusion.

PURPOSE: Acute central retinal artery occlusion (CRAO) induces ischaemic retinal oedema. The purpose of this study was to define sensitivity and specificity of optical coherence tomography (OCT) based retinal thickness analysis in determining ischaemia onset in CRAO. METHODS: The relative retinal thickness increase (RRTI) in comparison with the fellow eye was analysed retrospectively in OCT scans of 66 patients diagnosed with CRAO between January 2010 and December 2019 within 48 hr of ischaemia onset. The natural course of RRTI and the sensitivity and specificity of OCT-based determination of ischaemia onset in identifying CRAO within 4.5 hr using the RRTI were evaluated. RESULTS: Relative retinal thickness increase (RRTI) in acute CRAO follows a hyperbolic curve with a steep incline within the early phase after which it reaches a plateau. Optical coherence tomography (OCT)-based retinal thickness analysis in CRAO allows to differentiate patients with ischaemia onset within the past 4.5 hr or thereafter with a sensitivity of 100% and a specificity of 94.3%. CONCLUSION: Relative retinal thickness increase (RRTI) allows to identify CRAO patients that are eligible for a potentially beneficial reperfusion therapy within a therapeutic window of 4.5 hr with a high accuracy. Especially in patients with unknown ischaemia onset, this diagnostic tool could be of major importance in the future clinical management.

New Scheimpflug Dynamic In Vivo Curve Analyses to Characterize Biomechanical Changes of the Cornea After Cross-linking for Progressive Keratoconus.

PURPOSE: To evaluate the effect of corneal cross-linking (CXL) in progressive keratoconus by applying in vivo static and dynamic Scheimpflug analyses. METHODS: In this longitudinal retrospective study, corneal topography and tomography (Pentacam HD) and dynamic Scheimpflug-based biomechanical analyses (CorvisST [CST]) of 24 eyes of 24 patients with progressive keratoconus before and 6 months after CXL were reviewed. New dynamic curve analyses, provided by Oculus Optikgeräte, were performed to analyze corneal dynamics throughout the entire response to the CST air puff impulse. RESULTS: Besides subtle changes of topography and tomography, only the CorvisST predefined parameters peak distance (-0.5 mm) and radius of the intended cornea (+0.5 mm; P < .05) demonstrated statistically significant differences 6 months after CXL. Using new dynamic curve analyses, additional distinct changes of the corneal biomechanical characteristics after CXL were noted. CONCLUSIONS: Published results of corneal biomechanical changes after CXL for progressive keratoconus based on single, predefined CST parameters are inconsistent. The new dynamic curve analyses demonstrate distinct changes of the biomechanical properties of the cornea and might therefore be the next step in understanding in vivo analyses of corneal biomechanics.

Screening for Subclinical Keratoconus Using Swept-Source Fourier Domain Anterior Segment Optical Coherence Tomography.

PURPOSE: To discriminate between subclinical fellow eyes of patients with keratoconus (scKCE) and normal eyes (NE) using swept-source Fourier-domain anterior segment optical coherence tomography (SS-OCT). SETTING: University Medical Center Hamburg-Eppendorf, Germany. DESIGN: Retrospective cross-sectional study. METHODS: NE (both eyes with a KISA% Index <60; N = 213) and scKCE (KISA% Index <60, but an index of >100 in the fellow eye; N = 61) eyes were grouped according to the KISA% Index. Topography and tomography data were obtained by SS-OCT (Casia SS1000) and reviewed retrospectively. Receiver operating characteristics were performed for Casia SS1000 integrated automated parameters and newly computed indices. Additionally, discriminant functions were calculated for the automated single parameters, the computed indices, and the combination of both. RESULTS: An accuracy ≥0.7 was reached for 28 (8 automated and 20 newly computed parameters) of 785 parameters. Fourier analysis posterior higher-order irregular astigmatism revealed the highest accuracy with 0.81. By combining automated parameters with the newly computed indices in 1 discriminant function, an area under the curve of 0.92 with a corresponding accuracy of 0.85 was achieved. CONCLUSIONS: SS-OCT is able to discriminate between NE and scKCE with high accuracy. Automated single parameters and newly computed indices were combined to further improve this accuracy.

Corneal biomechanical changes after crosslinking for progressive keratoconus with the corneal visualization scheimpflug technology.

Purpose. To evaluate the effect of corneal crosslinking in progressive keratoconus by applying in vivo corneal visualization Scheimpflug technology. Design. Longitudinal retrospective study. Subjects and Controls. Seventeen eyes of patients treated with corneal crosslinking for progressive keratoconus. Methods. Corneal visualization Scheimpflug technology analyses (research software version 6.07r08) of subjects with progressive keratoconus before and 3 months after corneal crosslinking (CXL) were reviewed retrospectively. t-test (for normal distribution) and Wilcoxon matched-pairs test (if not normally distributed) were used to test for statistically significant differences between pre- and post-CXL analyses. Results. We demonstrated statistically significant differences for the intraocular pressure (median: +3 mmHg, P = 0.004), the central corneal pachymetry (pachy; mean: -35 µm, P < 0.001), the timespan between the air impulse release and the first applanation of the cornea (A1time; median: +0.12 ms, P < 0.05), and the timespan between the air impulse release and the second applanation of the cornea (A2time; median: -37 ms, P < 0.05). Conclusions. With the A1time and the A2time, we identified two parameters that demonstrated a statistically significant improvement of the biomechanical properties of the cornea after CXL. Despite the known initial decrease of the pachymetry after CXL, none of the analyzed parameters indicated a progression of the keratoconus.