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Andrew J. Bower, Tao Liu, Zhuolin Liu, Nancy Aguilera, Joanne Li, Rongwen Lu, John Giannini, Steven Cornelissen, Alfredo Dubra, Daniel Hammer, Johnny Tam; Direct comparison of photoreceptor reflectivity measurements using simultaneous adaptive optics SLO and OCT. Invest. Ophthalmol. Vis. Sci. 2021;62(8):26.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the similarities and differences in reflectivity of individual cone photoreceptors as seen by adaptive optics (AO) scanning light ophthalmoscopy (AO-SLO) in comparison to AO-optical coherence tomography (AO-OCT).
Simultaneous, co-registered AO-SLO and AO-OCT images unaffected by transverse or longitudinal chromatic aberration were acquired from three subjects at eccentricities from 2.5° to 10° temporal. Images were acquired using a custom multimodal AO ophthalmoscope in which 10% of the 1080 nm light returning from the eye was captured for AO-SLO using a custom-developed avalanche photodiode (Boston Micromachines), with the remaining 90% of 1080 nm light used for AO-OCT. Following manual identification of photoreceptors, the following measurements corresponding to single cones were extracted: (1) AO-SLO intensity, (2) AO-OCT inner segment/outer segment (IS/OS) junction intensity, (3) AO-OCT cone outer segment tip (COST) intensity, and (4) AO-OCT outer segment projection intensity. In addition, outer segment length was measured as the intensity peak-to-peak distance between the IS/OS and COST of each cone.
The variable reflectivity observed in the cone photoreceptor mosaic matched well between the AO-SLO and AO-OCT projection images. AO-SLO intensities of 500 cones identified in the images were significantly correlated with outer segment projection intensity in AO-OCT (p<0.01, F-test on linear regression), with stronger correspondence of the AO-SLO intensity to IS/OS intensity compared to COST intensity. Both the IS/OS and COST layers could be observed in 91% of cones. In the remaining 9% of cones, only a single reflection in the IS/OS was observed with no apparent corresponding COST reflection. When both IS/OS and COST reflections were observed, the IS/OS reflection was brighter for 88% of cones. There was no apparent relationship between AO-SLO reflectivity and outer segment length (p>0.01, F-test on linear regression).
The use of a shared 1080 nm light source for simultaneous acquisition of AO-SLO images and AO-OCT volumes enables direct comparison of cone reflectivity across two inherently co-registered modalities. We show that cone reflectance on AO-SLO images arises more strongly from the IS/OS band, which may have implications for our understanding of cone waveguiding properties and their disc shedding processes.
This is a 2021 ARVO Annual Meeting abstract.
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