Functional optical coherence tomography for nonmydriatic intrinsic signal optoretinography of human photoreceptors

Abstract

Physiological dysfunction of diseased cells might occur prior to detectable morphological abnormalities such as retinal cell damage and thickness change. Functional assessment of photoreceptor physiology is essential for the early detection of eye diseases. It is desirable to develop a high-resolution method for objective assessment of photoreceptor physiology. Functional intrinsic optical signal (IOS) imaging, also known as optoretinography (ORG) or optophysiology, measures transient light changes correlated with retinal neural activities. The photoreceptor-IOS arises promptly after the beginning of stimulation, which ensures a unique biomarker for objective ORG measurement of physiological conditions of retinal photoreceptors. In this study, the feasibility of functional optical coherence tomography (OCT) imaging of fast photoreceptor-IOS in human photoreceptors has been demonstrated. The fast photoreceptor-IOS occurred before stimulus-evoked pupillary response and thus allows nonmydriatic ORG of human photoreceptors. The outer segment (OS) was confirmed as the source of fast photoreceptor-IOS by depth-resolved OCT. The active IOS changes were found at both OS boundaries, which connected to the inner segment and retinal pigment epithelium. This supports that the mechanism of the fast photoreceptor-IOS can be explained by transient OS shrinkage due to phototransduction.