Retinal angiography with real-time speckle variance optical coherence tomography

Abstract

This report describes a novel, non-invasive and label-free optical imaging technique, speckle variance optical coherence tomography (svOCT), for visualising blood flow within human retinal capillary networks. This imaging system uses a custom-built swept source OCT system operating at a line rate of 100 kHz. Real-time processing and visualisation is implemented on a consumer grade graphics processing unit. To investigate the quality of microvascular detail acquired with this device we compared images of human capillary networks acquired with svOCT and fluorescein angiography. We found that the density of capillary microvasculature acquired with this svOCT device was visibly greater than fluorescein angiography. We also found that this svOCT device had the capacity to generate en face images of distinct capillary networks that are morphologically comparable with previously published histological studies. Finally, we found that this svOCT device has the ability to non-invasively illustrate the common manifestations of diabetic retinopathy and retinal vascular occlusion. The results of this study suggest that graphics processing unit accelerated svOCT has the potential to non-invasively provide useful quantitative information about human retinal capillary networks. Therefore svOCT may have clinical and research applications for the management of retinal microvascular diseases, which are a major cause of visual morbidity worldwide.

In vivo optical imaging of human retinal capillary networks using speckle variance optical coherence tomography with quantitative clinico-histological correlation

“…The svOCT images were processed using the GPU-accelerated program (Xu et al, 2014(Xu et al, , 2015, and the retinal layers were automatically segmented using a 3D Graph Cut based segmentation tool implemented in Matlab (Lee et al, 2012). En face retinal network images were generated from the same 4 capillary networks using the morphometric criteria described above.…”

“…En face visualisation of the retinal microvasculature was processed and displayed in real-time ( Fig. 1A) using our open source GPU algorithm for svOCT (Xu et al, 2014(Xu et al, , 2015. Scan dimensions were calibrated based on the eye length of each participant, measured using the Zeiss IOLMaster 500 (IOL master 500, Carl Zeiss, Jena, Germany).…”

Quantifying Variability in Longitudinal Peripapillary RNFL and Choroidal Layer Thickness Using Surface Based Registration of OCT Images

“…15,16 Each image consisted of 400 B-scans, with 400 A-scans per B-scan and 1024 pixels per A-scan. The axial voxel resolution was 2.7 μm, the axial coherence length was 6 μm, and the lateral resolution ranged from 11.9 μm to 14.5 μm depending on the eye's axial length.…”

Strip-based registration of serially acquired optical coherence tomography angiography

“…5 The OCT system used a 1060-nm swept source (Axsun Inc.) with 100 kHz A-scan rate and a 111-nm 10-dB tuning bandwidth; the digitized spectrum used for imaging corresponded to an axial resolution of ∼6 μm in tissue. The size of the focal waist on the retina was estimated using the GullstrandLeGrand model of the human eye to be ω 0 ≈ 7.3 μm (calculated using Gaussian optics) corresponding to a lateral FWHM of ∼8.6 μm.…”

“…Variants of OCT-A methods have been described in recent review articles. [1][2][3][4] We have recently validated the speckle variance approach to OCT-A against standard invasive techniques, such as fluorescein angiography (FA), 5,6 in which only the superficial capillaries can be distinguished due to excessive choroidal fluorescence 7 and ex vivo histological analyses. 6,[8][9][10] The noninvasive, in vivo visualization of the retinal microvasculature using OCT-A can be instrumental in studying the onset and development of retinal vascular diseases.…”