HYPEROPIA CORRECTION BY NONCONTACT HOLMIUM-YAG LASER THERMAL KERATOPLASTY CLINICAL-STUDY WITH 2-YEAR FOLLOW-UP

Background: Thermal keratoplasty to correct hyperopia has been attempt ed with nonlaser and laser devices. Problems have included long-term r egression and irregular induced astigmatism. The present clinical stud y 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 h yperopia. Methods: Seventeen patients underwent noncontact holmium:YAG laser thermal keratoplasty in their nondominant eyes for correction o f hyperopia of up to 3.00 diopters, Treatment parameters included simu ltaneous delivery of eight holmium:YAG laser spots in a symmetrical oc tagonal array with a centerline diameter of 6 mm, 10 pulses of laser l ight 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 Sne llen visual acuity improved from 20/125-1 to 20/50-2. The mean change in spherical equivalent of subjective manifest refraction was -0.79 di opter. Eleven of these 15 eyes (73%) had a mean refractive correction of -1.1 diopters(range, -0.38 to -2.63 diopters); regression between 1 4 days and 2 years was 0.2 diopter. Four eyes (27%) had no persistent refractive correction (within +/- 0.25 diopter). Mean induced refracti ve astigmatism was 0.18 diopter. None of the eyes lost two or more lin es of spectacle-corrected distance vision. The amount of refractive co rrection at 2 years after surgery was correlated to the treatment puls e energy and the volume of the opacified corneal tissue observed immed iately after treatment. Conclusions: This technique of noncontact lase r thermal keratoplasty produced safe, effective, and persistent correc tions of low hyperopia in the majority of treated eyes.