Evaluation of a unique cw laser in radial thermokeratoplasty

Colin L. Smithpeter; Ashley J. Welch; Henry Grady Rylander III

doi:10.1117/12.147515

24 June 1993 Evaluation of a unique cw laser in radial thermokeratoplasty

Colin L. Smithpeter, Ashley J. Welch, Henry Grady Rylander III

Proceedings Volume 1877, Ophthalmic Technologies III; (1993) https://doi.org/10.1117/12.147515
Event: OE/LASE'93: Optics, Electro-Optics, and Laser Applications in Scienceand Engineering, 1993, Los Angeles, CA, United States

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.

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Colin L. Smithpeter, Ashley J. Welch, and Henry Grady Rylander III "Evaluation of a unique cw laser in radial thermokeratoplasty", Proc. SPIE 1877, Ophthalmic Technologies III, (24 June 1993); https://doi.org/10.1117/12.147515

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KEYWORDS

Cornea

Continuous wave operation

Sapphire

Birefringence

Pulsed laser operation

Eye

Laser vision correction

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