Adaptive Optics Optical Coherence Tomography Research Articles

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.

Adaptive optics-optical coherence tomography: optimizing visualization of microscopic retinal structures in three dimensions

Adaptive optics-optical coherence tomography (AO-OCT) permits improved imaging of microscopic retinal structures by combining the high lateral resolution of AO with the high axial resolution of OCT, resulting in the narrowest three-dimensional (3D) point-spread function (PSF) of all in vivo retinal imaging techniques. Owing to the high volumetric resolution of AO-OCT systems, it is now possible, for the first time, to acquire images of 3D cellular structures in the living retina. Thus, with AO-OCT, those retinal structures that are not visible with AO or OCT alone (e.g., bundles of retinal nerve fiber layers, 3D mosaic of photoreceptors, 3D structure of microvasculature, and detailed structure of retinal disruptions) can be visualized. Our current AO-OCT instrumentation uses spectrometer-based Fourier-domain OCT technology and two-deformable-mirror-based AO wavefront correction. We describe image processing methods that help to remove motion artifacts observed in volumetric data, followed by innovative data visualization techniques [including two-dimensional (2D) and 3D representations]. Finally, examples of microscopic retinal structures that are acquired with the University of California Davis AO-OCT system are presented.

Adaptive-optics optical coherence tomography for high-resolution and high-speed 3D retinal in vivo imaging

We have combined Fourier-domain optical coherence tomography (FD-OCT) with a closed-loop adaptive optics (AO) system using a Hartmann-Shack wavefront sensor and a bimorph deformable mirror. The adaptive optics system measures and corrects the wavefront aberration of the human eye for improved lateral resolution (~4 μm) of retinal images, while maintaining the high axial resolution (~6 μm) of stand alone OCT. The AO-OCT instrument enables the three-dimensional (3D) visualization of different retinal structures in vivo with high 3D resolution (4×4×6 μm). Using this system, we have demonstrated the ability to image microscopic blood vessels and the cone photoreceptor mosaic.