ULTRASOUND BIOMICROSCOPY OF INTRASTROMAL PHOTOREFRACTIVE KERATECTOMY WITH THE ND-YLF PICOSECOND LASER

PURPOSE: To evaluate corneal morphology in vivo following intrastromal photorefractive keratectomy (IPRK) with the Nd:YLF picosecond laser, using the ultrasound biomicroscope. MATERIALS AND METHODS: Myopic intr astromal PRK was performed in the anterior stroma of cat corneas with the neodymium:yttrium lithium fluoride (Nd:YLF) picosecond laser. Peri odic examination of the treated corneas up to 6 months postoperative w as performed with high resolution ultrasound biomicroscopy. Corneal th ickness, depth of the laser patterns from the corneal surface, alignme nt of the laser treatment, extent of stromal opacification until resol ution, and contour of the corneal surface were measured with the ultra sound biomicroscope throughout follow up. RESULTS: The treated corneas were thickened on ultrasonic biomicroscopy measurement immediately af ter intrastromal PRK and revealed a densely echogenic shadow parallel to the corneal surface at the treatment site. There was increased stro mal echogenicity denoting mild edema. The echoes decreased over time a nd appeared thinner at 2 months compared to the preoperative and immed iate postoperative measurements. At 6-month follow up, the treated cor neas were echolucent on ultrasonic biomicroscopy. CONCLUSION: The ultr asound biomicroscope might become a helpful tool in assessing accuracy of treatment parameters of intrastromal PRK as well as in monitoring the response of the cornea to treatment.