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Chan Wen, Jianqin Lei, Cheng Pei; The effect of axial length and signal strength on the measurement of peripapillary capillaries based on swept source optical coherence tomography angiography.. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2855.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the effect of axial length (AL) and signal strength on the measurement of vessel length density (VLD) of optic nerve head and peripapillary capillaries based on swept source optical coherence tomography angiography (SSOCTA).
This is a cross-sectional study that included only healthy volunteers. One eye was randomly chosen from each participant to be imaged with SSOCTA (Triton, OCTARA 1.0) using a 3×3mm scan pattern centered on the optic disc. The en face image of optic nerve head (ONH) was used for analysis and no segmentation was corrected. Image was excluded if the signal strength was less than 50 or there's obvious motion artifact or central deviation. All images were processed with a multi-scale Hessian filter, an auto-threshold (Otsu), subtraction of large vessels and skeletonization based on Image J. VLD was calculated on 5 locations including the ONH (a 1.5-mm circle manually centered on the disc) and 4 radial peripapillary areas (superior (S), nasal (N), inferior (I) and temporal (T)) between a 2.25-mm circle and the 1.5-mm circle. AL was measured by IOL Master. Pearson's test was used to assess the correlation between AL, signal strength and the VLD.
Ninety-eight eyes from 98 healthy Asian participants (23 males and 75 females, mean age 26.0±6.1 years) were involved in this study. The mean AL was 25.0±1.3 mm and the mean signal strength was 62.7±4.8 . The mean VLD measured on ONH , S , N , I and T was 16.8±1.9, 22.6±2.0, 23.0±2.8, 22.7±2.0 and 25.7±2.2 mm-1 . Axial length was significantly correlated with VLD on ONH (r=0.4, P<0.001), I (r=0.3, P=0.003) and T (r=0.2, P=0.025). While signal strength was not correlated with measurement of VLD on any location.
Axial length could positively affect the measurement of VLD on optic nerve head, inferior and temporal radial peripapillary areas based on SSOCTA. While signal strength did not affect the measurement.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
The above is an original scan of left optic disc and the bottom one is a skeletonization image with subtracting large vessels.
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