Page 179 - Demo

The eye as a window to the brain1776performed the retinal blood vessel assessments (A.A.). Images of the right eye were used for analyses. In case the quality was poor, the left eye image was used.Four vascular parameters were calculated, as described previously:12, 16, 20, 21 central retinal artery and central retinal vein equivalent (CRAE and CRVE; both measures of vessel diameter), fractal dimension (FD; measure of the branching pattern and vessel density) and vascular tortuosity (measure of the vessel trajectory). Vessel length was determined with customized semi-automated MATLAB 2022a software (MathWorks, Inc., Natick, Massachusetts, United States). 20CRAE and CRVE were calculated with the revised Knudtson‐Parr‐Hubbardformula and averaged over the six largest arterioles and venules in the zone between 0.5- and 2-disc diameters from the optic disc.22 In order to adjust for magnification differences of the two cameras, image resolution and refractive errors, a calibration factor was multiplied by individual CRAE and CRVE to convert values in pixels to micrometers (μm).12 FD was calculated with automated MATLAB 2018a software, using the box-counting method, in which images are divided into multiple equally sized square boxes. 23 The number of boxes containing the skeletonized line tracing was counted and the process was repeated for different sized squares. FD was calculated as the gradient of logarithms of the number of boxes and the size of the boxes.16 Vascular tortuosity was calculated as the ratio of the arc length (i.e., actual length of the vessel) divided by the chord length (i.e., length of a straight line drawn from the start to end point of the vessel, Figure 1) averaged over all vessels. 24, 25Optical coherence tomographyAn HRA+OCT Spectralis Tracking Laser Tomography camera (Heidelberg Engineering, United States of America) was used to obtain peripapillary RNFL thickness and macular thickness. Thickness of peripapillary RNFLwas evaluated as a 3.4 mm diameter circle surrounding the optic disk which was segmented into four sectors: superior, inferior, temporal, and nasal (Figure 2). The superior and inferior sectors were further divided into temporal-superior, nasal-superior, temporal-inferior and nasal-inferior