The Journal of Japan Society for Laser Surgery and Medicine

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We developed a temperature monitoring method with high-time resolution by means of auto-fluorescence measurement in order to monitor photorefractive keratectomy (PRK), quantitatively and qualitatively. We obtained calibration function to estimate the temperature which indicated sudden elevation induced by ArF excimer laser irradiation using tryphophan (Trp) solution as a cornea fluorescence model. We could fit the theoretical relation between fluorescence and temperature to the auto-fluorescence measurement results with correlation coefficient of 0.99 arranging the activation energy and the ratio of frequency factor to radiative rate of the Trp solution to 8.9kcal/mol, 4.6×10⁶, respectively. Since these values closed to reported values, we thought that developed temperature calibration method was appropriate. When AfF excimer laser was irradiated to the Trp solution at the fluence of 28-180mJ/cm2, temperature elevation was estimated to 4-32K. This temperature elevation of Trp solution agreed with a simple heat deposition calculation. Sampling depth was less than 5nm. The estimated temperature corresponded to the temperature at about 20ns after AfF excimer laser irradiation. We demonstrated that our method was unique high-time resolution, non-invasive and non-contact temperature monitoring method during ArF excimer laser irradiation to the cornea model. The present method has a potential application for monitoring ablation depth and ablation side effects during PRK.

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