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H Lubatschowski, A Heisterkamp, T Mamon, W Drommer, H Welling, W Ertmer; Intrastromal Corneal Surgery with Ultrashort Laser Pulses . Invest. Ophthalmol. Vis. Sci. 2002;43(13):144.
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Purpose: Femtosecond (fs) photodisruption opens new pathways in refractive surgery due to its gentle and precise interaction mechanism with biological tissue. With ultra-short laser pulses extremely precise cuts can be generated inside the corneal stroma in order to prepare corneal flaps and lenticules (fs-LASIK). Method: As a laser source, a titanium:sapphire laser system was used generating 160 fs - 1 ps pulses at a wavelength of 780 nm and a repetition rate of 3 kHz. The focal spot diameter inside the corneal stroma was approximately 4 µm at a pulse energy of 0.7µJ. On enucleated porcine eyglobes as well as on the eyes of three living rabbits a myopic correction (-3 to -5 dpts) was performed. The irradiated corneae were examined by light and electron microscopy. Results: The precision of the laser generated intrastromal cuts increases with decreasing laser pulse energy and pulse duration. Near the threshold for optical breakdown, microdissection of the corneal stroma could be performed with sub-µm precision. The amount of thermal damage of the irradiated tissue is below 1 µm. At high pulse intensities and small numerical apertures of the focusing lens, intrastromal streaks inside the treated eyes were found as a new side effect. This could be attributed to the non linear interaction mechanism with the corneal tissue. Conclusion: The quality of tissue processing by fs-photodisruption is comparable with the quality seen on ArF excimer laser ablation. The precision of the laser generated intrastromal cuts enable this procedure to correct refractive errors as well as to prepare donator and recipient tissue for keratoplasty with a much higher flexibility of what is known from the use of mechanical knifes.
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