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Justin V Migacz, Raju Poddar, Robert J Zawadzki, Ala Moshiri, Susanna S Park, Lawrence S Morse, John S Werner; Vascular pathologies in the chorioretinal complex investigated by swept-source phase variance optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5019.
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© ARVO (1962-2015); The Authors (2016-present)
In order to investigate the in vivo, depth-resolved, vasculature maps of chorioretinal complex of age related macular degeneration (AMD) in the human eye, a new swept-source phase variance optical coherence tomography (pvOCT) system was developed. This study examines the clinical utility of the pvOCT system with a case series of macular disease.
Five eyes were imaged with pvCOCT, including 4 eyes of AMD and 1 eye with reticular pseudodrusen. The imaging system used a swept-source laser (Axsun Inc., Billerica, USA) operating at 1060 nm with a sweep repetition rate of 100 kHz. The system provided axial resolution of 5.4 µm in tissue. Phase variance (PV) data were calculated from sets of 3 B-scans acquired at each location (BM-scans) in the volume. These data highlight motion at each cross-section, primarily the flow of blood cells, yielding the depth and size of vessels within the retina. 3x3mm2 and 1.5x1.5mm2 areas around the diseased region were scanned with densities of 360 BM-scans consisting of 440 A-lines each. Volumes required 4.4 seconds to acquire. Bulk motion removal and histogram-based thresholding were implemented to remove bulk motion artifacts. The en face, projections of the data produce two-dimensional vascular maps of specific layers depth sections in the retina.
Figure 1 shows a representative case of AMD (volume scan over 1.5x1.5mm2 at 3° nasal retina). The OCT intensity (a), phase variance (b), and fluorescein angiography (c) images are shown. En face phase variance angiography images of the chorioretinal complex of sections I-IV, from (b) are shown in (d)-(g), respectively, as well as a color composite in (h). A lack of PV signal within the druse sight (arrow in b) demonstrates that there is no visible blood flow directly below the RPE. In (f), the localized reduction in PV signal (white arrow) may be due to focal ischemia in the Sattler’s layer under the druse site. The FA image (c) and its PV counterpart (d) have similar visualizations of the vessels although the PV image has higher contrast and can reveal some capillaries (yellow arrows) not seen by FA.
The swept-source pvOCT system can noninvasively visualize vasculature maps of the chorioretinal complex. The vasculature pattern has good correlation with FA but is depth-resolved. It promises to provide valuable investigative information of macular diseases.
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