Optophysiology: Depth-resolved probing of retinal physiology with functional ultrahigh-resolution optical coherence tomography

Noncontact, depth-resolved, optical probing of retinal response to visual stimulation with a <10-μm spatial resolution, achieved by using functional ultrahigh-resolution optical coherence tomography (fUHROCT), is demonstrated in isolated rabbit retinas. The method takes advantage of the fact that physiological changes in dark-adapted retinas caused by light stimulation can result in local variation of the tissue reflectivity. fUHROCT scans were acquired from isolated retinas synchronously with electrical recordings before, during, and after light stimulation. Pronounced stimulus-related changes in the retinal reflectivity profile were observed in the inner/outer segments of the photoreceptor layer and the plexiform layers. Control experiments (e.g., dark adaptation vs. light stimulation), pharmacological inhibition of photoreceptor function, and synaptic transmission to the inner retina confirmed that the origin of the observed optical changes is the altered physiological state of the retina evoked by the light stimulus. We have demonstrated that fUHROCT allows for simultaneous, noninvasive probing of both retinal morphology and function, which could significantly improve the early diagnosis of various ophthalmic pathologies and could lead to better understanding of pathogenesis

Laser/Light Applications in Neurology and Neurosurgery

Applications of light in neurology and neurosurgery can be diagnostic or therapeutic. Neurophotonics is the science of photon interaction with neural tissue. Photodynamic therapy (PDT) has been attempted to destroy infiltrative tumor cells in tissue. Spatially modulated imaging (MI) is a newly described non-contact optical technique in the spatial domain. With this technique, both quantitative mapping of tissue optical properties within a single measurement and cross sectional optical tomography can be achieved rapidly. The ability to control the activity of a defined class of neurons has the potential to advance clinical neuromodulation