In situ Monitoring of Laser Modification Process in Human Cataractous Lens and Porcine Cornea Using Coherence Tomography

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Abstract
We demonstrate that optical coherence tomography (OCT) is a convenient diagnostic tool to monitor pulse-to-pulse kinetics in laser interactions with biological tissue. In experiments on laser modification and ablation of the cataractous human lens and the porcine cornea we have applied this technique in situ to investigate different modes of preablation tissue swelling, crater formation and thermally affected zone development. The cataractous lens is an example of highly scattering media whereas the cornea is initially low scattering. The radiation with different wavelengths has been employed including that of a YAG:Er laser (λ=2.94 μm), a glass:Er laser (λ=1.54 μm), YAG:Nd lasers (λ=1.32 μm and λ=1.44 μm), as well as of the fifth harmonic of a Nd:YAP laser (λ=0.216 μm). Pulse-to-pulse OCT monitoring has been accompanied by the probe beam shielding diagnostics to provide the time-resolved observation of the interaction dynamics. © 1999 Society of Photo-Optical Instrumentation Engineers.