  Delayed dark adaptation due to impaired rod photoreceptor homeostasis has
been reported as the earliest symptom of eye diseases such as age-related
macular degeneration, diabetic retinopathy, and retinitis pigmentosa. Objective
measurement of dark adaptation can facilitate early diagnosis to enable prompt
intervention to prevent vision losses. However, there is a lack of noninvasive
methods capable of spatiotemporal monitoring of photoreceptor changes during
dark adaptation. Here we demonstrate functional optical coherence tomography
(OCT) for in vivo intrinsic signal optoretinography (ORG) of dark adaptation
kinetics in the C57BL/6J mouse retina. Functional OCT revealed a shortening of
the outer retina, a morphological change in the cone and rod photoreceptor
interdigitation zone, and a reduction in intrinsic signal amplitude at the
photoreceptor inner segment ellipsoid. A strong positive correlation between
morphophysiological activities was also confirmed. Functional OCT of dark
adaptation kinetics promises a method for rapid ORG assessment of physiological
integrity of retinal photoreceptors.
