Combining adaptive optics with optical coherence tomography: unveiling the cellular structure of the human retina in vivo

Optical coherence tomography (OCT) represents a noninvasive, high axial resolution imaging technique that provides a unique insight for clinicians into structures of the normal and diseased human retina in vivo. Similar to all ophthalmic instruments, imaging has to be performed through the optics of the eye (i.e., cornea and lens), which show natural imperfections and therefore introduce aberrations. In OCT this results in a degradation of transverse resolution limiting the instrument's ability to detect small structures (e.g., single cells). Adaptive optics (AO) is capable of compensating for these aberrations (both static and dynamic) to achieve nearly diffraction-limited transverse resolution. Therefore, a combination of AO with OCT results in a powerful imaging system capable of resolving the cellular 3D architecture of the human retina in vivo. This review describes the basic principles of OCT and AO instruments, as well as the integration of AO into OCT systems together with recent experimental results obtained with this new technology. Additionally, the review includes a discussion of remaining technical problems associated with AO-OCT in retinal imaging, followed by an outlook of possible further developments.