Setup for femtosecond laser corneal surgery

Abstract : Purpose: The authors present a microsurgery experimental system using Nd: Glass femtosecond laser. It is coupled to a confocal microscopy observation system to investigate intrastromal effects of the femtosecond laser. Methods: The femtosecond laser is a CPA system with a regenerative amplifier delivering pulses at a wavelength of 1.065 µm, with a pulse duration of 500 fs, an energy of 60 µJ for a repetition rate of 10 KHz. The amplified pulses power fluctuations are lower than 1%. Pulses repetition rate is adjustable up to 10kHz and can even be reduced to single shot. The laser beam has a Gaussian distribution shape TEM00. The obtainable peak power density is on the order of 10^15W/cm^2. The laser beam travels to the samples guided by one six–lens set and one magnifier. The last lens can be changed to adjust the focal distance from 2 to 5 cm and the focal spot from 1 to 4 µm. The samples are fixed to an anterior chamber system, which is driven by a micrometric precision motor system. The 3 dimensional movements are computer controlled. The laser energy is continuously monitor for measurements consistency. The experimental set up is also composed of a confocal microscope, which permits corneal sample analysis without removing them from the artificial chamber system. Results: The experimental set up permits complex geometry to be done. Penetrating and lamellar cuts could be performed in silicon dioxide and human corneal samples. The confocal microscopy observation system permits precise parameter control of the cutting system (cut shape, shot scanning and treatment depth). Conclusions: Applications for femtosecond laser are the refractive surgery and corneal keratoplasty. The development of concepts as sutureless keratoplasty needs an experimental system with large flexibility in order to work out useful cut parameters.