Non-invasive in vivo measurement of retinal physiology with high-speed ultrahigh resolution OCT

Non-invasive in vivo functional optical imaging is demonstrated using high-speed, ultrahigh resolution optical coherence tomography (UHR-OCT). A high-speed, UHR-OCT system using spectral/Fourier domain detection was developed for functional imaging experiments in the rodent retina. Using a spectrally multiplexed superluminescent diode light source, imaging was performed with 2.8 μm resolution at a rate of 24,000 axial scans per second. OCT measurement protocols were designed to minimize noise sources that cause undesired fluctuations in the measured OCT signal. A white light stimulus was applied to the retina and the average reflectivity from each intraretinal layer was monitored over time using OCT. A white light stimulus induces a response consisting of an increase in the reflectance of the photoreceptor outer segments. To our knowledge, this is the first in vivo demonstration of functional imaging using OCT in the retina. Further systematic investigation will be required to fully characterize the observed optical changes. Eventually, this may prove to be an objective method for measuring photoreceptor function in the human retina.