Reversible isomerization of rhodopsin imaged in-vivo with phase-sensitive OCT

Vision begins with photoisomerization, triggering conformational changes in opsins. Microelectrode recordings are invasive and insensitive to early receptor potential in rods. Phase-sensitive OCT (optoretinography, ORG) enables noninvasive label-free detection of nanoscale cellular deformations caused by physiological processes. Green flashes induce rapid contraction of the rod outer segments, while UV flashes elicit an opposite response. These deformations are explained as electromechanical manifestations of charge transfer across rod disc membranes during isomerization into Meta II (green) and Meta III (UV). ORG reveals rhodopsin dynamics with greater sensitivity than electrical methods, offering insights into visual transduction and potential for early diagnosis of photoreceptor dysfunction.