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Significance: Multiple eye diseases such as age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa can cause photoreceptor dysfunction. Rod photoreceptors are known to be more vulnerable than cone photoreceptors. Therefore, functional assessment of rod photoreceptors is important for early detection of eye diseases. Aim: This study is to demonstrate the feasibility of using intrinsic optical signal (IOS) optoretinography (ORG) for objective detection of dark adaptation (DA) abnormality due to rod photoreceptor degeneration. Approach: Functional optical coherence tomography (OCT) was employed for IOS ORG of wild-type (WT) and retinal degeneration 10 (rd10) mice. Six WT C57BL/6J and eight rd10 B6.CXB1-Pde6brd10/J mice at postnatal day 14 (P14) were used for this study. Dynamic OCT analysis of retinal thickness and brightness changes, corresponding to light to dark transition, was implemented Results: Comparative measurement of the retina under light and dark conditions revealed significant IOS changes within the outer retina. The thickness between external limiting membrane (ELM) and retinal pigment epithelium (RPE) reduced, and the OCT brightness of inner segment ellipsoid zone (EZ) decreased during DA, compared to light adaptation (LA). Relative EZ intensity change was observed to decrease larger in rd10, compared to WT. The relative intensity of the hyporeflective band between ELM and RPE also showed significant decrease in rd10 retinas during DA. Conclusions: DA-IOS abnormalities were observed in rd10, compared to WT at P14. The ORG measurement of DA-IOS kinetics promises valuable information for noninvasive assessment of photoreceptor function.

Intrinsic optical signal (IOS) imaging of the retina, also termed as optoretinography (ORG), promises a noninvasive method for objective assessment of retinal function. By providing unparalleled capability to differentiate individual layers of the retina, functional optical coherence tomography (OCT) has been actively investigated for intrinsic signal ORG measurements. However, clinical deployment of functional OCT for quantitative ORG is still challenging due to the lack of a standardized imaging protocol and the complication of IOS sources and mechanisms. This article aims to summarize recent developments of functional OCT for ORG measurement, OCT intensity- and phase-based IOS processing. Technical challenges and perspectives of quantitative IOS analysis and ORG interpretations are discussed.

This study is to characterize reflectance profiles of retinal blood vessels in optical coherence tomography (OCT), and to validate these vascular features to guide artery-vein classification in OCT angiography (OCTA) of human retina. Depth-resolved OCT reveals unique features of retinal arteries and veins. Retinal arteries show hyper-reflective boundaries at both upper (inner side towards the vitreous) and lower (outer side towards the choroid) walls. In contrary, retinal veins reveal hyper-reflectivity at the upper boundary only. Uniform lumen intensity was observed in both small and large arteries. However, the vein lumen intensity was dependent on the vessel size. Small veins exhibit a hyper-reflective zone at the bottom half of the lumen, while large veins show a hypo-reflective zone at the bottom half of the lumen, Comment: 11 pages, 4 figures