Signal and resolution enhancements in dual beam optical coherence tomography of the human eye.

In the past 10 years, a dual beam version of partial coherence interferometry has been developed for measuring intraocular distances in vivo with a precision on the order of 0.3 to 3 μm. Two improvements of this technology are described. A special diffractive optical element allows matching of the wavefronts of the divergent beam reflected at the cornea and the parallel beam reflected at the retina and collimated by the optic system of the eye. In this way, the power of the light oscillations of the interfering beams incident on the photodetector is increased and the signal-to-noise ratio of in vivo measurements to the human retina is improved by 20 to 25 dB. By using a synthesized light source consisting of two spectrally displaced superluminescent diodes with an effective bandwidth of 50 nm, and by compensating for the dispersive effects of the ocular media, it was possible to record the first optical coherence tomogram of the retina of a human eye in vivo with an axial resolution of ∼6 to 7 μm. This is a twofold improvement over the current technology. © 1998 Society of Photo-Optical Instrumentation Engineers.