Hyperopia Correction by Noncontact Holmium.YAG Laser Thermal Keratoplasty: Clinical Study with Two-year Follow-up

Abstract

Background: Thermal keratoplasty to correct hyperopia has been attempted with nonlaser and laser devices. Problems have included long-term regression and irregular induced astigmatism. The present clinical study was performed to investigate the safety, efficacy, and stability of a noncontact mode of holmium:YAG laser energy delivery and a modified laser thermal keratoplasty treatment procedure for correction of low hyperopia.Methods: Seventeen patients underwent noncontact holmium:YAG laser thermal keratoplasty in their nondominant eyes for correction of hyperopia of up to 3.00 diopters. Treatment parameters included simultaneous delivery of eight holmium:YAG laser spots in a symmetrical octagonal array with a centerline diameter of 6 mm, 10 pulses of laser light at 5-Hz pulse repetition frequency, and pulse energies of 159 to 199 mJ. Follow-up was 2 years in 15 of 17 patients.Results: In the 15 eyes examined at 2 years after surgery, mean uncorrected distance Snellen visual acuity improved from 20/125-1 to 20/50-2. The mean change in spherical equivalent of subjective manifest refraction was -0.79 diopter. Eleven of these 15 eyes (73%) had a mean refractive correction of -1 .1 diopters (range, -0.38 to -2.63 diopters); regression between 14 days and 2 years was 0.2 diopter. Four eyes (27%) had no persistent refractive correction (within ± 0.25 diopter). Mean induced refractive astigmatism was 0.18 diopter. None of the eyes lost two or more lines of spectacle-corrected distance vision. The amount of refractive correction at 2 years after surgery was correlated to the treatment pulse energy and the volume of the opacified corneal tissue observed immediately after treatment.Conclusions: This technique of noncontact laser thermal keratoplasty produced safe, effective, and persistent corrections of low hyperopia in the majority of treated eyes.