Abstract
Femtosecond near-infrared lasers are widely used for a number of ophthalmic procedures, with flap cutting in the laser-assisted in situ keratomileusis (LASIK) surgery being the most frequent one. At the same time, lasers of this type, equipped with harmonic generators, have been shown to deliver enough ultraviolet (UV) power for the second stage of the LASIK procedure, the stromal ablation. However, the speed of the ablation reported so far was well below the currently accepted standards. Our purpose was to perform high-speed photorefractive keratectomy (PRK) with femtosecond UV pulses in rabbits and to evaluate its predictability, reproducibility and healing response. The laser source delivered femtosecond 206 nm pulses with a repetition rate of 50 kHz and an average power of 400 mW. Transepithelial PRK was performed using two different ablation protocols, to a total depth of 110 and 150 μm. The surface temperature was monitored during ablation; haze dynamics and histological samples were evaluated to assess outcomes of the PRK procedure. For comparison, analogous excimer ablation was performed. Increase of the ablation speed up to 1.6 s/diopter for a 6 mm optical zone using femtosecond UV pulses did not significantly impact the healing process.
Highlights
Since the first appearance of near infrared (NIR) femtosecond lasers in refractive surgery as a tool for flap creation,[1] the number of applications for these lasers in ophthalmic surgery has grown significantly
After upgrading the laser system, the myopic corneal ablation speed in rabbit corneas increased by nearly a factor of four compared with the laser setup used in our previous experiments.[18]
The healing process and its outcomes in terms of haze and histopathology evaluations were similar to those described in our previous study, in which we compared the outcomes at 1 month after femtosecond UV (180 Æ 5 mW, 20 kHz) or excimer ablation.[18]
Summary
Since the first appearance of near infrared (NIR) femtosecond lasers in refractive surgery as a tool for flap creation,[1] the number of applications for these lasers in ophthalmic surgery has grown significantly. It is possible to complete at least myopic correction using only the femtosecond laser,[2,3] this procedure still has not made pulsed ultraviolet (UV) lasers obsolete. The excimer laser has been the laser source of choice for photorefractive keratectomy (PRK) since the introduction of the procedure;[4,5] later on, it took a choice position in laserassisted in situ keratomileusis (LASIK)-type surgeries.
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