Retinal Imaging With Adaptive Optics High Speed and High Resolution Optical Coherence Tomography

Abstract

Abstract: : Purpose: OCT is a powerful optical sectioning technique commonly used in retinal imaging to achieve high axial resolution (up to 3 µm), but it is limited in its transverse resolution by the small size of the eye’s pupil and by ocular wavefront aberrations. The coupling of AO technology to OCT offers the possibility to obtain images with high transverse and high axial resolution. Methods: Fourier domain optical coherence tomography was achieved using a superluminescent diode centered at 840 nm and 50 nm optical bandwidth (6 µm axial resolution) operating at 10.000 A–scans/s (10 Frames/s, 1000A–scans/Frame). This system was combined with a closed–loop AO system to quantify and correct higher–order wavefront aberrations using a Hartmann–Shack sensor at 30 Hz and a high–stroke 35– actuator bimorph deformable mirror. Results: Adaptive optics OCT offers improved in vivo imaging of small structures lying within retinal layers and greater differentiation between retinal layers. Closed–loop real–time correction of ocular aberrations, achieved for a 6 mm pupil diameter permits lateral resolution close to the theoretical diffraction limit. A significant signal–to–noise improvement with OCT is possible when correcting higher–order aberrations using AO. First results on healthy normal subjects as well as selected patients will be presented. Conclusions: The combination of AO and high–speed Fourier domain OCT offers the potential to increase sensitivity and transverse resolution as compared to imaging with OCT alone. High acquisition speed combined with improved transverse resolution is expected to yield three–dimensional visualization of retinal features at resolutions hitherto possible only with histological samples.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • anatomy • retina