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Zhihong Hu, Wongsiri Taweebanjongsin, Ziyuan Wang, Julian Weichsel, Michel Teussink, Srinivas Sadda; Comparison of High Resolution and High Speed OCTA Axial Profiles in Normal Eyes. Invest. Ophthalmol. Vis. Sci. 2020;61(7):5340.
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© ARVO (1962-2015); The Authors (2016-present)
While in standard transverse optical coherence tomography angiography (OCTA) en face analysis, the signal is averaged over predefined retinal vascular slabs, in axial OCTA analysis it is averaged over the transverse directions and subsequently the resulting axial profiles are analyzed in depth. OCTA axial profiles may be sensitive to detect changes in the microvasculature at different depth in the setting of disease even in high speed OCT acquisitions at lower transverse resolution (but still preserving original OCT high resolution axially). The purpose of this study is to compare the OCTA axial profiles in high resolution and high speed OCT scans in normal eyes to assess if acquisition time can be reduced without significant loss of information in OCTA axial profiles.
Seventeen macular OCTA images from healthy subjects were captured with a Spectralis HRA + OCT device (Heidelberg Engineering) in both high resolution mode (768 A-scans x 768 B-scans, 15° x 15°, 4.4 mm x 4.4 mm) and high speed mode (384 A-scans x 384 B-scans, 15°x15°, 4.4 mm x 4.4 mm), respectively. For both modes, the OCTA axial signal (vessel density) at each depth position was assessed within 4 fovea-centered concentric rings located at 2.5°- 3.75°, 6.25°-7.5°, 10° - 11.25°, and 13.75° - 15°.
Figure 1 shows the en face OCTA images of the superficial vascular complex from a high speed and a high resolution scans. Although the reduced resolution is apparent, the overall vascular pattern is unchanged. Figure 2 demonstrates the OCTA axial vascular profiles in the 4 concentric ring locations using high speed and high resolution modes. Comparison of the profiles shows that they are very similar with respect to number of peaks, shape/width of the peaks, and the axial position of the peaks.
Although the high speed mode has reduced transverse resolution, its axial signal profiles are very similar to those obtained with high resolution mode in normal eyes. If these findings are confirmed in eyes with disease, this suggests that axial OCTA analysis may be performed in high speed images for better efficiency in regard to both acquisition time and patient comfort.
This is a 2020 ARVO Annual Meeting abstract.
Superficial en face OCTA maps from high speed (Left) and high resolution (Right)
Comparison of axial vascular profiles in the 4 concentric rings. Left column: 4 ring positions. Middle column: Axial signals in high speed. Right column: Axial signals in high resolution.
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