Optical coherence tomography angiography of perilimbal vasculature: validation of a standardised imaging algorithm

Abstract

PurposeTo test the reliability and accuracy of a standardised non-invasive imaging algorithm using optical coherence tomography angiography (OCTA) in detecting and quantifying pharmacologically induced changes in the perilimbal vasculature.MethodsIn this prospective observational imaging study, 370 angiograms of 15 normal eyes and 10 eyes with nasal pterygiums were obtained using a commercially available OCTA system with split-spectrum amplitude-decorrelation angiography technology. Postprocessing of the images to quantify the area occupied by the blood vessels was performed using the Fiji software. The main outcome measures were reliability (intraobserver and interobserver agreement) and accuracy of the standardised algorithm in detecting and quantifying relative change (vasoconstriction and vasodilatation) in the area occupied by the blood vessels after instillation of topical vasoconstrictors.ResultsThe intraclass correlation coefficients for intraobserver and interobserver agreement were 0.91 and 0.88 (good to excellent), respectively. In normal eyes, significant vasoconstriction was noted at 5 min (35%–47%) after application of eye-drops, which peaked at 10 min (43%–63%) and was sustained until 20 min (35%–51%), followed by gradual recovery. Greatest effect was noted with a combination of 5% phenylephrine and 0.15% brimonidine tartrate (BT) eye-drops as compared with either one or two drops of BT alone, both at the 10 min (p=0.0058) and 20 min (p=0.0375) time points. This dose-dependent temporal trend was replicated in eyes with primary nasal pterygium (p=0.31).ConclusionsThe findings suggest that OCTA can reliably and accurately detect and quantify relative changes in the perilimbal vasculature in both normal eyes and in eyes with pterygium.

High-Resolution Optical Coherence Tomography Angiography Characteristics of Limbal Stem Cell Deficiency

“…HR-OCTA was performed by a technician using the AngioVue OCTA system (Optovue, Inc., Fremont, CA, USA) in all four limbal quadrants (superior, inferior, nasal and temporal) with adjoining bulbar conjunctiva. The technique of HR-OCTA imaging that the authors performed has been explained by the authors previously [ 17 ]. Twelve parameters that were analysed for each quadrant on OCT and OCTA imaging were: (i) epithelial thickness ( Figure 2 ), (ii) stromal thickness, (iii) ratio of epithelial thickness to stromal thickness, (iv) mean and mode of epithelial reflectivity ( Supplementary file ), (v) mean and mode of stromal reflectivity ( Supplementary file ), (vi) ratio of mean and mode of stromal reflectivity, (vii) mean total limbal vascular density, (viii) mean superficial limbal vascular density ( Figure 3 ), (ix) mean total vascular density into bin distribution, (x) mean superficial vascular density into bin distribution, (xi) ratio of segmented to total vascular density, and (xii) maximum peak bin distribution frequency in total and segmented vascular density.…”

“…Previous studies have reported the usefulness of HR-OCT in cases of LSCD by assessing the limbal epithelial thickness [ 13 ], for visualising palisades [ 14 ], and quantifying the limbal stem cell niche [ 15 ]. Recently, the HR-OCT angiography (OCTA) has been used for the anterior segment for imaging corneal neovascularisation [ 16 ], limbal and peri-limbal vasculature [ 17 ]. However, features on HR-OCT and HR-OCT angiography that are sensitive and specific for LSCD, and could be used for diagnosis of LSCD have not yet been determined.…”

Regenerative Approaches and Future Trends for the Treatment of Corneal Burn Injuries

“…Otherwise, two main molecular imaging approaches have been reported consisting in targeting of specific inflammation markers, such as VCAM-1, fibrin, thrombin and MMPs [60,71] and ex vivo labelling of macrophages [72,73]. Recent studies have also revealed the role of non-contact imaging modalities for limbal injury and corneal wound healing [74,75]. Among these, a very promising approach to image the vasculature in the eye districts is represented by Optical Coherence Tomography Angiography (OCT-A), a showed that OCT-A can reliably and accurately detect as well as quantify relative changes in the perilimbal vasculature, hence distinguishing between healthy eyes and eyes with pterygium [74].Taken together, the results of these studies are very promising, even though none of these strategies have yet been translated to the clinic.…”

“…Among these, a very promising approach to image the vasculature in the eye districts is represented by Optical Coherence Tomography Angiography (OCT-A), a technology based on laser light reflectance of moving red blood cells to obtain high resolution images of surface vessels without using exogenous dyes. Recently, Patel et al showed that OCT-A can reliably and accurately detect as well as quantify relative changes in the perilimbal vasculature, hence distinguishing between healthy eyes and eyes with pterygium [74].Taken together, the results of these studies are very promising, even though none of these strategies have yet been translated to the clinic.…”

Role of anterior segment optical coherence tomography angiography in the assessment of acute chemical ocular injury: a pilot animal model study

“…Optical coherence tomography angiography (OCTA) is a rapid, non-contact imaging technique that can help delineate ocular vasculature 10 – 14 . Whilst existing OCTA systems were not specifically designed for imaging the anterior segment, they can be adapted to assess cornea or iris vasculature, i.e.…”