Noncontact laser photothermal keratoplasty I: Biophysical principles and laser beam delivery system

J. M. Parel, Q. Ren, G. Simon

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

BACKGROUND: Thermal shrinkage of stromal collagen is known to produce changes in the corneal curvature. We designed a novel, noncontact laser beam delivery system to perform laser photothermal keratoplasty. MATERIALS AND METHODS: The instrument consistent of a pulsed holmium:YAG laser (2.10- micrometer wavelength, 250-microsecond pulse width, 5-hertz repetition rate) coupled via a monofilament fiber to a common slit-lamp microscope equipped with a polyprism, an adjustable mask, and a projection lens. The system projected an 8-spot annular pattern of infrared laser energy on the cornea to achieve a thermal profile within the stroma and to attain controlled, predictable collagen shrinkage. The system produced treatment patterns of 8 to 32 spots of 150 to 600 μm diameter in concentric rings, continuously adjustable between 3 and 7 mm. The versatility of the system in creating different treatment patterns was tested on thermal paper and human cadaver eyes. RESULTS: A uniform beam profile and different treatment patterns for myopia, hyperopia, and astigmatism were obtained. Myopic correction of 6.00 diopters was demonstrated on cadaver eyes. Corneal topography documented corneal flattening (> 6.00 D) with the following treatment parameters: each spot size on the cornea = 300 μm, radiant exposure of each spot = 18.0 J/cm2, number of pulses = 1, diameter of the treatment ring = 3 mm. CONCLUSIONS: Noncontact slit-lamp microscope laser delivery system for laser photothermal keratoplasty provides flexible and precise selection of laser treatment parameters. It may improve the efficacy of the procedure.

Original languageEnglish (US)
Pages (from-to)511-518
Number of pages8
JournalJournal of Refractive and Corneal Surgery
Volume10
Issue number5
StatePublished - 1994

ASJC Scopus subject areas

  • Ophthalmology

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