Proceedings Article | 20 February 2006
KEYWORDS: Adaptive optics, Optical coherence tomography, Eye, Retina, Tissue optics, Tomography, Imaging systems, Interferometry, Wavefronts, Image resolution
Since the advent of Adaptive Optics in ophthalmic instrumentation, several attempts for improving the performances of the existing observing techniques, either in imaging or tomography, have been made. For long, Adaptive Optics have proven its ability to restore high lateral resolution with the SLO or flood imaging, or more recently to enhance the interferometric contrast and hence, the sensitivity, of OCT. Nevertheless, the direct acquisition of en face tomographic images equivalent to horizontal optical sections of the retinal tissue is still the objective of intensive developments. We report here a new instrumental approach where a time domain full field OCT setup has been coupled with a double pass adaptive optics system, providing 300 x 300 x 4 μm instantaneous optical sections of biological tissues. We will describe how the interferometric contrast is derived without any modulation of the optical path, thus giving access to targets as critical, because unstable, as the retinal tissue during in vivo ophthalmic examinations. The advantages of this new design, which benefits from the implementation of very recent deformable mirrors, featuring simultaneously a higher actuators density and a much larger stroke, will be discussed, and the ability of the system to accommodate for variable pupil sizes, thanks to wavefront sensing techniques optimized for ophthalmology, are commented. The performances of the system, in terms of X,Y,Z resolution, sensitivity, registration capability and / or image stabilisation are discussed and illustrated with results obtained in the laboratory and in clinical environment.
