Purpose: This study was performed to evaluate the safety and effectiveness of noncontact holmium: YAG (Ho:YAG) laser thermal keratoplasty (LTK) for correcting low to moderate hyperopia.
Methods: Twenty-eight patients were treated unilaterally to correct low to moderate hyperopia (up to +3.88 diopters [D] refractive error) using simultaneous noncontact delivery of Ho:YAG laser energy. Treatment parameters included one or two symmetric octagonal rings of eight spots per ring with centerline 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 energy, ranging from 208 to 242 mJ. Follow-up was 1 year in 26 (93%) of the 28 patients.
Results: At 1 year postoperatively, uncorrected distance visual acuity was improved in all patients. The mean change in subjective 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 approximately 6 months. In the one-ring treatment group (17 eyes), refractive corrections of -0.50 to -1.13 D were achieved in ten eyes (59%), and seven eyes (41%) were unchanged (within +/- 0.25 D) relative to their preoperative measurements. In the two-ring treatment group, all eight 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 visual acuity. These was no clinically significant change in endothelial cell density with respect to preoperative values. Glare and contrast sensitivity 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.
Conclusions: This initial United States clinical study with 1-year follow-up indicates that noncontact LTK treatment of low hyperopia is safe and effective, providing persistent, though modest, refractive corrections in 59% of the one-ring group and larger, persistent, refractive corrections in 100% of the two-ring group.