PICOSECOND LASER IN-SITU KERATOMILEUSIS WITH A 1053-NM ND-YLF LASER

BACKGROUND: Excimer laser in situ keratomileusis requires a microkerat ome to generate an anterior corneal flap, plus an excimer laser to abl ate the underlying stromal tissue. In this paper we introduce the conc epts of laser flap formation and in situ keratomileusis using a picose cond laser. METHODS: A neodymium-doped yttrium-lithium-fluoride (Nd:YL F) laser with a plano-plano quartz applanation lens was used to genera te various patterns of intrastromal photodisruption in human donor eye s to fashion anterior corneal flaps and generate intrastromal lenticul es. RESULTS: Smooth intrastromal dissections, 6 mm in diameter, were g enerated 160 mu m below the corneal surface when the laser delivered p ulses at 1 kHz with energies of either 40 mu J/pulse or 60 mu J/pulse, placed 20 inn apart in an expanding spiral. This enabled us to fashio n anterior corneal flaps. The ease of the surgery and quality of the d issection corresponded well, and it was evident that both deteriorated noticeably when the laser pulses were separated by 25 mu m or 30 mu m , regardless of pulse energy. Using 40 mu J laser pulses placed 20 mu m apart we also created a 5-mm diameter, 320 mu m thick (130 mu m - 45 0 mu m deep) stromal lenticule below a corneal flap that was easily ex tracted when the flap was raised. CONCLUSIONS: Anterior corneal flaps were easily fashioned using a Nd:YLF laser. Picosecond laser in situ k eratomileusis with a Nd:YLF laser could offer a favorable alternative to combined microkeratome/excimer laser in situ keratomileusis.