Ablation spectra of the human cornea

Ablation of human corneal tissue with 193 nm excimer laser energy generates fluorescence in the near ultraviolet and visible regions of the spectrum. The fluorescence spectra from five human corneas were collected during abla tion in vitro. We find that the fluorescence spectrum changes continuously as the cornea is ablated from the epithelial surface towards the endotheliu m. We reduced the dimensionality of the large data set resulting from each cornea by a principal components analysis. The three most significant princ ipal component eigenvectors suffice to describe the observed spectral evolu tion, and independent analysis of each tissue sample produces a similar set of eigenvectors. The evolution of the calculated eigenvector weighting fac tors during ablation then corresponds to the observed spectral evolution. I n fact, this evolution is qualitatively consistent between corneas. We sugg est that this spectral evolution offers promise as a real-time surgical fee dback tool. (C) 2001 Society of Photo-Optical Instrumentation Engineers.