Wavelength Optimization in Femtosecond Laser Corneal Surgery

International audiencePURPOSE. To evaluate the influence of wavelength on penetration depth and quality offemtosecond laser corneal incisions in view of optimizing procedures in corneal surgeryassisted by ultrashort pulse lasers.METHODS. We performed penetrating and lamellar incisions on eye bank corneas using severalultrashort pulse laser sources. Several wavelengths within the near-infrared and shortwaveinfraredwavelength range were used and the pulse energy was varied. The corneas weresubsequently analyzed using light microscopy as well as transmission and scanning electronmicroscopy.RESULTS. We found higher penetration depths and improved incision quality when usingwavelengths close to k ¼ 1650 nm rather than the wavelength of k ¼ 1030 nm typical incurrent clinical systems. Optical micrographs show an improvement of the penetration depthby a factor of 2 to 3 while maintaining a good incision quality when using the longerwavelength. These results were confirmed with micrographs obtained with transmission andscanning electron microscopy.CONCLUSIONS. A wavelength change from the standard 1030 nm to 1650 nm in corneal surgeryassisted by ultrashort pulse laser considerably reduces light scattering within the tissue. Thisresults in a better preservation of the laser beam quality in the volume of the tissue,particularly when working at depths required for deep lamellar or penetrating keratoplasty.Using this wavelength yields improved penetration depths into the tissue; it permits use oflower energies for any given depth and thus reduces unwanted side effects as thermal effects