title: 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 6mm, 10 pulses of laser light at 5-Hz pulse repetition frequency, and pulse energies of 159 to 199mJ. 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.
authors.affiliation: Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: D D
authors.initials: DD
authors.lastname: Koch
authors.forename: A
authors.initials: A
authors.lastname: Abarca
authors.forename: R
authors.initials: R
authors.lastname: Villarreal
authors.forename: R
authors.initials: R
authors.lastname: Menefee
authors.forename: T
authors.initials: T
authors.lastname: Kohnen
authors.forename: A
authors.initials: A
authors.lastname: Vassiliadis
authors.forename: M
authors.initials: M
authors.lastname: Berry
mesh_terms: D000368:Aged; D015350:Contrast Sensitivity; D003315:Cornea / Q000033:anatomy & histology / Q000601:surgery*; D016039:Corneal Transplantation / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006695:Holmium; D006801:Humans; D006956:Hyperopia / Q000601:surgery*; D007429:Intraocular Pressure; D053685:Laser Therapy; D008297:Male; D008875:Middle Aged; D017060:Patient Satisfaction; D011183:Postoperative Complications; D012449:Safety; D014792:Visual Acuity
chemical_list: D006695:Holmium