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April 1995

Myopic Intrastromal Photorefractive Keratectomy With the Neodymium-Yttrium Lithium Fluoride Picosecond Laser in the Cat Cornea

Author Affiliations

From the Cornea Service, Department of Ophthalmology, The New York Eye and Ear Infirmary, New York (Drs Habib and Speaker and Mr Kaiser), and the Department of Physics, University of California, Irvine (Dr Juhasz). Drs Habib and Speaker and Mr Kaiser have no financial interest in the products discussed in this study. Dr Juhasz is a consultant to Intelligent Surgical Lasers Inc.

Arch Ophthalmol. 1995;113(4):499-505. doi:10.1001/archopht.1995.01100040121037

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 di-opters and pachymetric thinning of 50 μm 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.

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