OCT functions as a type of optical biopsy, providing information on retinal pathology in situ and in real time, with resolutions approaching that of excisional biopsy and histopathology. The development of ultrabroad-bandwidth and tunable light sources, as well as high-speed Fourier detection techniques, has enabled a significant improvement in ophthalmic optical coherence tomography (OCT) imaging performance. Three-dimensional, ultrahigh-resolution OCT (UHR OCT) can provide information on intraretinal morphology that is not available from any other non-invasive diagnostic. High-speed imaging facilitates the acquisition of three-dimensional data sets (3D-OCT), thus enabling volumetric rendering and the generation of OCT fundus images that precisely and reproducibly register OCT images to fundus features. The development of broadband light sources emitting at new wavelengths, e.g., approximately 1050 nm, has enabled not only 3D-OCT imaging with enhanced choroidal visualization, but also reduced scattering losses and improved OCT performance in cataract patients. Adaptive optics using high-stroke, deformable mirror technology to correct higher order aberrations in the human eye, in combination with specially designed optics to compensate chromatic aberration along with three-dimensional UHR OCT, has recently enabled in vivo cellular-resolution retinal imaging. In addition, extensions of OCT have been developed to enhance image contrast and to enable non-invasive depth-resolved functional imaging of the retina, thus providing blood flow, spectroscopic, polarization-sensitive and physiological information. Functional OCT promises to enable the differentiation of retinal pathologies via localized, functional retinal response or metabolic properties. These advances promise to have a powerful impact on fundamental as well as clinical studies.