Functional optical coherence tomography of retinal morphophysiological changes during dark adaptation

Abstract

The retina is a light-sensing neural network, converting light energy to bioelectric signals for visual information processing. The retina is often damaged by neurodegeneration, which leads to severe vision loss. The initial symptoms of retinal neurodegenerative diseases are manifested by functional abnormalities. Delayed dark adaptation is one of the earliest functional symptoms of retinal neurodegeneration. Therefore, objective measurement of dark adaptation promises the early diagnosis of various retinal diseases. In this study, we demonstrate the feasibility of functional optical coherence tomography (OCT) imaging of the retina during dark adaptation <i>in vivo</i>. A custom-designed spectral-domain OCT was used in dark adaptation measurement, and two-month-old C57BL/6J mice were used in this study. We observed three image biomarkers. First, the outer retinal thickness became thinner during dark adaption. Second, OCT intensity of the inner segment ellipsoid zone was gradually decreased over time under darkness. Third, during dark adaptation, there was a rearrangement of the interdigitation zone between the outer segment and retinal pigment epithelium. Functional OCT enabled the concurrent measurement of retinal thickness changes and intrinsic optical signal (IOS) changes in the retina during dark adaptation. These functional biomarkers may help assess the early dysfunction of outer retinal neurons.