Plexus-specific effect of flicker-light stimulation on the retinal microvasculature assessed with optical coherence tomography angiography

Kallab, Martin; Hommer, Nikolaus; Tan, Bingyao; Pfister, Martín; Schlatter, Andreas; Werkmeister, René M.; Chua, Jacqueline; Schmidl, Doreen; Schmetterer, Leopold; Garhöfer, Gerhard

doi:10.1152/ajpheart.00495.2020

Cited by 15 publications

(11 citation statements)

References 36 publications

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“…Among these approaches, Hessian-based filtering has been shown to result in the best quality of final image [ 25 ]. Other works have employed a Frangi filter to improve visibility of vessels in OCTA images of the retina [ 49 ], choroid [ 67 ], and skin [ 41 ]. Despite its widespread use, the Frangi filter has also been criticized in some studies for introducing errors in the vessel architecture, either by missing vessels rendered in the image with low SNR or generating spurious vessels depending on the structure of the background noise [ 68 , 69 ].…”

Section: Discussionmentioning

confidence: 99%

“…We chose eight metrics to comprehensively characterize microvascular network architecture based on an extensive qualitative review of the literature, balancing coverage and overlap of characteristics [ 13 , 44 – 48 ]. These metrics allow users to obtain comprehensive information about the microvasculature [ 49 ]. Table 1 and Fig 3 give an overview of our selected metrics, how they are calculated, and indications of biological relevance.…”

Section: Methodsmentioning

confidence: 99%

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OCTAVA: An open-source toolbox for quantitative analysis of optical coherence tomography angiography images

et al. 2021

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Optical coherence tomography angiography (OCTA) performs non-invasive visualization and characterization of microvasculature in research and clinical applications mainly in ophthalmology and dermatology. A wide variety of instruments, imaging protocols, processing methods and metrics have been used to describe the microvasculature, such that comparing different study outcomes is currently not feasible. With the goal of contributing to standardization of OCTA data analysis, we report a user-friendly, open-source toolbox, OCTAVA (OCTA Vascular Analyzer), to automate the pre-processing, segmentation, and quantitative analysis of en face OCTA maximum intensity projection images in a standardized workflow. We present each analysis step, including optimization of filtering and choice of segmentation algorithm, and definition of metrics. We perform quantitative analysis of OCTA images from different commercial and non-commercial instruments and samples and show OCTAVA can accurately and reproducibly determine metrics for characterization of microvasculature. Wide adoption could enable studies and aggregation of data on a scale sufficient to develop reliable microvascular biomarkers for early detection, and to guide treatment, of microvascular disease.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

OCTAVA: An open-source toolbox for quantitative analysis of optical coherence tomography angiography images

et al. 2021

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“…2020; Kallab et al. 2021). This is of special importance, given that these larger vessels would contribute disproportionally to the OCT‐A signal and may mask subtle changes in the microcirculation.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, it has been hypothesized that in complex neural tissues, such as the retina, microvascular responses to metabolic stimuli are not distributed uniformly but vary locally with high spatial and temporal resolution (Kornfield & Newman 2014; Kallab et al. 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Evidence from other vascular beds such as those of the heart or the brain suggests that small resistance vessels respond differently compared to larger arterioles or feeder vessels (DeFily & Chilian 1995;Kulik et al 2008). Furthermore, it has been hypothesized that in complex neural tissues, such as the retina, microvascular responses to metabolic stimuli are not distributed uniformly but vary locally with high spatial and temporal resolution (Kornfield & Newman 2014;Kallab et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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Effect of hyperoxia and hypoxia on retinal vascular parameters assessed with optical coherence tomography angiography

Hommer

Kallab

Sim

et al. 2021

Acta Ophthalmologica

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To investigate the response of the superficial and deep capillary plexuses to hyperoxia and hypoxia using optical coherence tomography angiography (OCT-A) and retinal vessel analyzer.Methods: Twenty-four healthy volunteers participated in this randomized, double-masked, crossover study. For each subject, two study days were scheduled: on one study day, hyperoxia was induced by breathing 100% oxygen whereas on the other study day, hypoxia was induced by breathing a mixture of 88% nitrogen and 12% oxygen. Perfusiondensity wascalculated in the superficial vascular plexus (SVP) and the deep capillary plexus (DCP), using OCT-A before (normal breathing) and during breathing of the gas mixtures. Retinal vessel calibres in major retinal vessels were measured using a dynamic vessel analyzer.Results: During 100% oxygen breathing, a significant decrease in DCP perfusion density from 41.7 AE 2.4 a.u to 35.6 AE 3.1 a.u. (p < 0.001) was observed, which was accompanied by a significant decrease in vessel diameters in majorretinal arteries and veins(p < 0.001 each). No significant change in perfusion density in the SVP occurred (p = 0.33). In contrast, during hypoxia, perfusion density in the SVP significantly increased from 34.4 AE 3.0a.u.to 37.1 AE 2.2 a.u. (p < 0.001), while it remained stable in the DCP (p = 0.25). A significant increase in retinal vessel diameters was found (p < 0.01). Systemic oxygen saturation correlated negatively with perfusion density in the SVP and the DCP and retinal vessel diameters (p < 0.005 each). Conclusion:Our results show that systemic hyperoxia induces a significant decrease in vessel density in the DCP, while hypoxia leads to increased vessel density limited to the SVP. These results indicate that the retinal circulation shows the ability to adapt its blood flow to metabolic changes with high local resolution dependent on the capillary plexus.

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Assessment of alterations in the retina and vitreous in pre‐ and post‐COVID‐19 patients using swept‐source optical coherence tomography and angiography: A comparative study

Gao,

Zhang,

Mou

et al. 2023

Journal of Medical Virology

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Ocular manifestations have been well recognized in coronavirus disease 2019 (COVID‐19) outbreak. Several studies have detected ocular manifestations in patients after COVID‐19. However, little is known about the retinal and vitreal alterations in patients before and after COVID‐19 infection. This study aimed to investigate the retinal and vitreal alterations in patients before and after contracting COVID‐19 infection using swept‐source optical coherence tomography (SS‐OCT) and angiography (SS‐OCTA). A total of 38 participants (76 eyes) were enrolled and followed‐up 1 month after COVID‐19 infection. Then, 26 patients (52 eyes) were evaluated 3 months after COVID‐19 infection. Compared with the pre‐COVID‐19 status, patients with 1‐ and 3‐month post‐COVID‐19 statuses had significant thinning of ganglion cell and inner plexiform layer, thickening of inner nuclear layer, a decrease in the vessel density (VD) of superficial vascular complex, and an increase in the VD of deep vascular complex. Meanwhile, alteration in parameters of foveal avascular zone (all p < 0.05) and hyper‐reflective dots in the vitreous of 27 patients (54 eyes) (71.1% vs. pre‐COVID‐19, 34.2%, p = 0.006) were observed. These findings suggest significantly retinal and vitreal alterations occurred in patients after COVID‐19 infection, possibly due to direct or indirect virus‐induced injuries. Further longitudinal studies are required to investigate the long‐term effects of COVID‐19 infection on the human eyes.

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Plexus-specific effect of flicker-light stimulation on the retinal microvasculature assessed with optical coherence tomography angiography

Cited by 15 publications

References 36 publications

OCTAVA: An open-source toolbox for quantitative analysis of optical coherence tomography angiography images

OCTAVA: An open-source toolbox for quantitative analysis of optical coherence tomography angiography images

Effect of hyperoxia and hypoxia on retinal vascular parameters assessed with optical coherence tomography angiography

Assessment of alterations in the retina and vitreous in pre‐ and post‐COVID‐19 patients using swept‐source optical coherence tomography and angiography: A comparative study

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