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Proceedings Paper

Evaluation of a unique cw laser in radial thermokeratoplasty
Author(s): Colin L. Smithpeter; Ashley J. Welch; Henry Grady Rylander
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Paper Abstract

A unique continuous wave (cw) holmium laser ((lambda) equals 2.09 micrometers , Rare Earth Medical) has been evaluated as a new heating modality for thermokeratoplasty. Thermokeratoplasty is a refractive surgical procedure for the correction of hyperopia which uses selective heating to reshape the cornea. The holmium laser is highly effective in this procedure due to the high absorption coefficient ((mu) a equals 27.55 cm-1) of the cornea at 2.09 micrometers . The depth of corneal photocoagulation has been evaluated with histological studies of enucleated porcine eyes that were irradiated with the cw Ho:YAG laser. Laser power and exposure time ranged from 300 mW to 800 mW and 100 ms to 800 ms, respectively. The laser was delivered to the eyes via a 600 micrometers low-OH optical fiber. Coagulation depth was determined by birefringence microscopy of the corneal sections. Our studies also compared the effects of contact and non-contact irradiation and found significant advantages with the contact mode. The optimal laser parameters determined from the histology studies were used for in vivo rabbit studies to quantify the refractive correction possible. One coagulation was placed on each of sixteen equiangular rays taken from a central, clear, optical zone in the cornea with a diameter of 7 mm. Refractive changes in the central cornea were quantified with a keratoscope. Initial procedures resulted in refractive changes up to five diopters. The keratoscope results showed a significant regression at three weeks post- operatively.

Paper Details

Date Published: 24 June 1993
PDF: 7 pages
Proc. SPIE 1877, Ophthalmic Technologies III, (24 June 1993); doi: 10.1117/12.147515
Show Author Affiliations
Colin L. Smithpeter, Univ. of Texas/Austin (United States)
Ashley J. Welch, Univ. of Texas/Austin (United States)
Henry Grady Rylander, Univ. of Texas/Austin (United States)

Published in SPIE Proceedings Vol. 1877:
Ophthalmic Technologies III
Jean-Marie A. Parel; Qiushi Ren, Editor(s)

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