Marginal Corneal Vascular Arcades

Abstract

The MCA comprise a network of branched interlinked elliptical loops supporting circumferential blood flow in the corneal periphery. There was no definable change in vascular pattern extending into the limbal region.

Optical Coherence Tomography Angiography for Anterior Segment Vasculature Imaging

“…Because this is a relatively new technology developed for retinal use, we initially conducted a proof-ofconcept study of eyes of healthy subjects to determine the scan protocol, which produced substantially consistent scans of the corneolimbal vessels (k value, 0.76; ICC, 0.94). Although our corneal vascular measurements were similar in terms of consistency with those of a previous corneal indocyanine green angiography (ICGA) study (ICC, 0.67e0.83), 19 we recognize that several aspects such as age, gender, or other ocular factors may lead to variation in loop size and branching between subjects, even for similar corneal quadrants. 19 However, the aim of this study was not to describe the corneal vasculature in detail, but rather to demonstrate that this OCTA system may be adapted for anterior segment vasculature imaging with adequate consistency.…”

“…Although our corneal vascular measurements were similar in terms of consistency with those of a previous corneal indocyanine green angiography (ICGA) study (ICC, 0.67e0.83), 19 we recognize that several aspects such as age, gender, or other ocular factors may lead to variation in loop size and branching between subjects, even for similar corneal quadrants. 19 However, the aim of this study was not to describe the corneal vasculature in detail, but rather to demonstrate that this OCTA system may be adapted for anterior segment vasculature imaging with adequate consistency. We used the same scanning protocol to image eyes with abnormal corneal vasculature to confirm that the OCTA could successfully image aberrant blood vessels amid various important pathologic features, such as vascularization in a corneal graft that is associated with corneal graft rejection 22 and postherpetic keratitis, where its treatment is increasingly being evaluated using new antiangiogenic therapies.…”

“…25,26 Our findings support previous observations that vessels in the periphery of the cornea comprise a fine capillary network consisting of vascular loops with 3 to 4 branches, which are not as evident on slit-lamp images. 19 Although a previous study of corneal vascular arcades using ICGA was described in detail, these measurements were from various random quadrants of the corneal limbus. 19 In our study, we compared scans from each quadrant and found that there was a higher density of vascular loops in the temporal marginal corneal arcades compared with those in the nasal quadrants.…”

“…We then used a selective filter to highlight the linear structures such as blood vessels and to reduce the surrounding noise to export the resulting vascular tree as a binary image for further processing, similar to a previously described method. 19 Each ROI was assessed for the number of vascular loops (as illustrated in Fig 1), 6 vessel segments (previously defined as the section between 2 branch points or a terminal point), 19 fractal dimension (D f ) value, and the area enclosed by each vascular loop (square millimeters). 19,20 The quality of the scan images were assessed using the signal strength index and image quality score using a recognized system, that is, 0 to 4 (0, no vessel discernible; 1, poor vessel delineation; 2, good vessel delineation; 3, very good vessel delineation; 4, excellent vessel delineation) on 2 scans per quadrant, performed by 2 independent, masked assessors.…”

“…19 Each ROI was assessed for the number of vascular loops (as illustrated in Fig 1), 6 vessel segments (previously defined as the section between 2 branch points or a terminal point), 19 fractal dimension (D f ) value, and the area enclosed by each vascular loop (square millimeters). 19,20 The quality of the scan images were assessed using the signal strength index and image quality score using a recognized system, that is, 0 to 4 (0, no vessel discernible; 1, poor vessel delineation; 2, good vessel delineation; 3, very good vessel delineation; 4, excellent vessel delineation) on 2 scans per quadrant, performed by 2 independent, masked assessors. 20 We then used the scan protocol as derived above to perform OCTA imaging in 5 patients with various corneal pathologic features, namely, corneal neovascularization in a corneal graft, pterygium, postherpetic keratitis scar, lipid keratopathy, and limbal stem cell deficiency.…”