HYPEROPIA CORRECTION BY NONCONTACT HOLMIUM-YAG LASER THERMAL KERATOPLASTY - UNITED-STATES PHASE IIA CLINICAL-STUDY WITH A 1-YEAR FOLLOW-UP

Purpose: This study was performed to evaluate the safety and effective ness of noncontact holmium:YAG (Ho:YAG) laser thermal keratoplasty (LT K) for correcting low to moderate hyperopia. Methods: Twenty-eight pat ients were treated unilaterally to correct low to moderate hyperopia ( up to + 3.88 diopters [D] refractive error) using simultaneous noncont act delivery of Ho:YAG laser energy. Treatment parameters included one or two symmetric octagonal rings of eight spots per ring with centerl ine diameters of 6 mm (1 ring) or 6 and 7 mm (2 rings), ten pulses of laser light at 5-Hz pulse repetition frequency, and variable pulse ene rgy, ranging from 208 to 242 mJ. Follow-up was 1 year in 26 (93%) of t he 28 patients. Results: At 1 year postoperatively, uncorrected distan ce visual acuity was improved in all patients. The mean change in subj ective manifest refraction (+/- spherical equivalent [SE]) was -0.55 /- 0.33 D and -1.64 +/- 0.61 D for one- and two-ring treatment groups, respectively, with good stability in the refractive change after appr oximately 6 months. In the one-ring treatment group (17 eyes), refract ive corrections of -0.50 to -1.13 D were achieved in ten eyes (59%), a nd seven eyes (41%) were unchanged (within +/- 0.25 D) relative to the ir preoperative measurements. In the two-ring treatment group, all eig ht eyes (100%) had substantial refractive corrections (range, -0.75 to -2.50 D). Mean induced refractive astigmatism was 0.25 +/- 0.29 D and 0.47 +/- 0.53 D for one- and two-ring treatments, respectively. None of the eyes lost two or more lines of spectacle-corrected distance vis ual acuity. There was no clinically significant change in endothelial cell density with respect to preoperative values. Glare and contrast s ensitivity testing indicate that peripheral corneal opacities produced by LTK do not degrade vision. The amount of refractive change in each group was correlated with the amount of laser pulse energy. Conclusio ns: This initial United States clinical study with I-year follow-up in dicates that noncontact LTK treatment of low hyperopia is safe and eff ective, providing persistent, though modest, refractive corrections in 59% of the one-ring group and larger, persistent, refractive correcti ons in 100% of the two-ring group.