Myopic intrastromal photorefractive keratectomy with the neodymium-yttrium lithium fluoride picosecond laser in the cat cornea
M. S. Habib, M. G. Speaker, R. Kaiser and T. Juhasz
Department of Ophthalmology, New York Eye and Ear Infirmary, New York, USA.
OBJECTIVE: To evaluate the refractive effects of myopic intrastromal
photorefractive keratectomy (IPRK) with the neodymium-yttrium lithium
fluoride (Nd-YLF) picosecond laser. METHODS: A 1053-nm Nd-YLF picosecond
laser was used to produce myopic IPRK in cat corneas at threshold energy
densities. Preoperative corneal topography and ultrasonic pachymetry were
performed followed by IPRK in one eye each of 21 cats. No anti-inflammatory
medications were administered. Postoperative corneal topography, ultrasonic
pachymetry, and slit-lamp examination were performed at scheduled
intervals. RESULTS: An average topographic flattening of 11.4 diopters and
pachymetric thinning of 50 microns at the center of the treatment zone were
observed by 6 weeks following treatment. The average diameter of the zone
of flattening was 5.1 mm at 6 weeks and 6.0 mm at 12 weeks postoperatively.
At 6 months postoperatively, the average central corneal power was
unchanged, while the average central thickness had returned to the
preoperative value. A mild subepithelial haze was detected at 1 month
following IPRK, which was barely perceptible at the second through sixth
months. Regression of the topographic effects of PRK was not observed.
CONCLUSION: Intrastromal PRK with the Nd-YLF picosecond laser produces
central flattening of the cat cornea with barely perceptible stromal haze
and no regression of topographic effect after 6 months in the absence of
treatment with anti-inflammatory agents.
