Measurement of damage threshold of human anterior corneal layers irradiated by femtosecond laser pulses for corneal graft surgery

In this work, we concentrate on the accurate determination of the damage threshold of the epithelial and Bowman's layers of human corneal tissue. To this aim, we use a statistical approach, well adapted to the measurement of the laser damage threshold of a living tissue and giving further information concerning the deterministic character of femtosecond damage and thus the technical development of the laser process. In addition, the technique provides a quantitative measurement of the fluence range for which the damage occurrence is erratic. Determination of these thresholds is the key issue for the technical development of a laser-cut eye surgery process. Actually, the knowledge of the low threshold is required for fixing the laser fluence level for which the tissue integrity is preserved, and the determination of the high threshold is essential for the development of the cutting surgery process of the tissue. Indeed, we presume that the operating laser condition has to be related to the high fluence damage threshold or somewhat higher, depending on the targeted constraints of quality and efficiency of the surgery process.