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Venu Manne, Patricia Sha, Jochen Straub, Mary K Durbin; Sensitivity of Spectral Domain OCTA Imaging with Polarization and Beam defocus. Invest. Ophthalmol. Vis. Sci. 2016;57(12):464.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate the effect of polarization and beam defocus/ocular diopter setting on image quality of Optical Coherence Tomography Angiography(OCTA) scans acquired on CIRRUS HD-OCT Model 5000 (ZEISS Dublin, CA).
A commercial Cirrus HD-OCT Model 5000(ZEISS Dublin, CA) with software version 9.0 was used to acquire OCTA images on 5 eyes from healthy volunteers using OCTA 3x3 mm scan. For each eye the operator used the ‘Autofocus ’ and ‘Optimize’ features on the CIRRUS GUI to attempt to automatically find the optimal position to correct for refractive error and polarization, respectively. Using ‘Autofocus ’ and ‘Optimize’ features improves the scan image quality which is reflected in signal strength indicator for each scan. Signal strength ranges from 0 to 10, with 10 being maximum signal strength.From these optimal positions, the polarization paddle position was varied from 0 to 400 motor steps in steps of 50 and OCTA images were obtained at each step. Following that with optimal position for polarization, the ocular lens position was varied to correct for refractive error by +/-2.5 D in steps of 0.5 D, and OCT images were obtained at each step. FastTrack was used to maintain the scan position at the same location as the original optimized image.
Based on data from 5 eyes, when varying the polarization position, the signal strength varied from as low as 4 to maximum of 10. When varying the beam diopter position, the signal strength varied little between 9 and 10. In Figure 1, the retinal vessels are more easily resolved and better defined with a scan of higher signal strength, see image (a) vs image (d) as pointed by red arrows. OCTA scans with signal strength of 8 or better showed highly detailed views of the retinal vasculature, even with 2.5D of defocus.
OCTA image quality is affected by polarization and beam defocus . The ‘Autofocus ’ and ‘Enhance’ features in CIRRUS(ZEISS Dublin, CA) serve to optimize signal strength and quality of OCTA scans.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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