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Harsha L Rao, Jayasree P Venugopal, Robert N Weinreb, Zia Pradhan, Narendra K Puttaiah, Sathi Devi, Kaweh Mansouri, Carroll A B Webers; Repeatability of vessel density measurements of high-density optical coherence tomography angiography scans and their comparability with standard-density scans in normal and glaucoma eyes. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5068.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the repeatability of peripapillary vessel density (VD) measurements of high-density (HD) optical coherence tomography angiography (OCTA, RTVue XR OCT, Optovue Inc.) scans in normal and glaucomatous eyes, and to compare these VD measurements with those of standard-density (SD) OCTA scans.
In a cross-sectional study, 46 normal (33 subjects) and 89 glaucoma eyes (64 patients) underwent 3 HD (400x400 A-lines) and 1 SD (304x304 A-lines) optic nerve head OCTA scans (4.5x4.5 mm) in the same session. Repeatability of the VD measurements of HD scans was assessed using within-subject coefficient of repeatability (CRw) and coefficient of variation (CVw). Effect of signal strength index (SSI) on repeatability was evaluated with repeated measures mixed effects models. Agreement in VD measurements between HD and SD scans was assessed using Bland and Altman analysis.
CRw (%) and CVw (%) of peripapillary VD measurements of HD scans ranged from 3.2 to 6.7, and 2.6 to 4.8 respectively in glaucoma eyes. Repeatability estimates of most VD measurements were better in normal compared to glaucoma eyes. VD measurements significantly increased with increase in SSI of repeat scans (coefficients ranging from 0.17 to 0.37, p<0.001 for all associations). Therefore, the HD scan with a SSI closest to that of the SD scan, was used in the agreement analysis. Mean difference in the VD values between HD and SD scans ranged between 0.7% (temporal sector VD in normal) and 2.4% (superonasal sector VD in glaucoma), with HD scans showing significantly higher VD values than SD scans. The 95% limits of agreement (LoA) in glaucoma eyes ranged between -2.0% to 5.0% for whole enface VD and -4.8% to 9.6% for superotemporal VD.
Test-retest repeatability of VDs on HD scans was as high as 6%. VD of HD scans were higher than that of SD scans. The wide 95% LoA indicate that the VD measurements of HD and SD scans cannot be used interchangeably. These results should be considered while using OCTA for longitudinal evaluation in glaucoma.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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