Small cellular deformations associated with the changes of cell potential can reveal the underlying physiological activity. Using quantitative phase microscopy, we demonstrate deformations of up to 3nm during action potential in HEK cells, and ~1nm in primary cortical neurons. Phase-resolved OCT with adaptive optics in human eyes revealed rapid axial shrinkage of the cone outer segments, starting within 0.3ms after light stimulus, followed by a gradual expansion that saturates around 500ms. Characteristics of the rapid outer segment contraction are consistent with the early receptor potential, attributed to charge movement across the outer segment disc membranes during photoisomerization.
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