In vivo measurement of retinal physiology with high-speed ultrahigh-resolution optical coherence tomography

Noninvasive in vivo functional optical imaging of the intact retina is demonstrated by using high-speed, ultrahigh-resolution optical coherence tomography (OCT). Imaging was performed with 2.8 microm resolution at a rate of 24,000 axial scans per second. A white-light stimulus was applied to the dark-adapted rat retina, and the average reflectivities from different intraretinal layers were monitored as a function of time. A 10%-15% increase in the average amplitude reflectance of the photoreceptor outer segments was observed in response to the stimulus. The spatial distribution of the change in the OCT signal is consistent with an increase in backscatter from the photoreceptor outer segments. To our knowledge, this is the first in vivo demonstration of OCT functional imaging in the intact retina.