PhD student, Macquarie University
The ocular circulation provides readily visible information about the state of the systemic circulation. Pulse wave velocity in large arteries is commonly used as a clinical indicator of arterial stiffness. However, whether arterial stiffness at the microvascular level reflects systemic arterial stiffness remains unknown. My aim is to investigate the interaction between dynamic characteristics of retinal vessels, intraocular pressure (IOP) and systemic vascular characteristics. Studying dynamic characteristics of retinal vessels may aid in identifying new cardiovascular-related biomarkers as well as being potentially relevant to the pathogenesis of neurodegenerative disorders such as glaucoma and Alzheimer’s disease.
Abstract: To compare retinal vessel calibers extracted from phase-sensitive optical coherence tomography (OCT) images with vessel calibers as obtained from the Retinal Vessel Analyzer (RVA).Data from previously published studies in 13 healthy subjects breathing room air (n = 214 vessels) and 7 subjects breathing 100% oxygen (n = 101 vessels) were used. Vessel calibers from OCT phase images were measured vertically along the optical axis by three independent graders. The data from RVA fundus images were corrected for magnification to obtain absolute values.The average vessel diameter as obtained from OCT images during normoxia was lower than from RVA images (83.8 ± 28.2 μm versus 86.6 ± 28.0 μm, P < 0.001). The same phenomenon was observed during 100% oxygen breathing (OCT: 81.0 ± 22.4 μm, RVA: 85.5 ± 26.0 μm; P = 0.001). Although the agreement between the two methods was generally high, the difference in individual vessels could be as high as 40%. These differences were neither dependent on absolute vessel size nor preferably found in specific subjects. Interobserver differences between OCT evaluators were much lower than differences between the techniques.Extracting vessel calibers from OCT phase images may be an attractive approach to overcome some of the problems associated with fundus imaging. The source of differences in vessel caliber between the two methods remains to be investigated. In addition, it remains unclear whether OCT-based vessel caliber measurement is superior to fundus camera-based imaging in risk stratification for systemic or ocular disease. (ClinicalTrials.gov numbers, NCT00914407, NCT02531399.).
Pub.: 14 Jul '16, Pinned: 30 Aug '17
Abstract: An optical coherence tomography (OCT) microvascular imaging platform, consisting of Doppler (DOCT) and speckle variance (svOCT) modalities, and microvascular image quantification tools are developed. The quantification methods extract blood flow-related parameters from DOCT images and vessel morphological parameters from svOCT images. This platform is used to assess the microvascular (DOCT and svOCT) images obtained during a clinical study on late oral radiation toxicity. This specific pathology was considered a suitable scenario for verifying the performance of the developed quantification platform because late oral radiation toxicity is known to involve microvascular damage. The derived parameters are compared between several DOCT and svOCT images from one patient and one healthy volunteer as proof-of-principle, and the significance of the observed differences is discussed. Given the low number of OCT clinical studies that measure and quantify microvascular images and considering the importance of such quantification in a number of pathologies, this newly developed platform can serve as a useful tool in studying diseases and treatments with microvascular involvement.
Pub.: 12 Jul '13, Pinned: 30 Aug '17