title: Intrastromal photorefractive keratectomy for myopia by Nd:YLF picosecond laser.
abstract: BACKGROUND
  An intrastromal photorefractive keratectomy (ISPRK) by Nd:YLF Picoseconds Laser has been performed on 17 eyes with corrected visual acuity of 20/200 or worse. The purpose of this study was to study the safety and effectiveness of ISPRK using different laser parameters.
  
  
  METHODS
  The Neodymiun Yttrium Lithium Fluoride laser system (Nd:YLF) was used to perform the myopic treatment. We studied the effect of pattern depth, the numbers of patterns, the thickness of a single spiral pattern, the distance between two patterns along Z axis, the pattern curvature perpendicular to the Z axis, the energy, the spatial density, and the repetition frequency of the laser pulse.
  
  
  RESULTS
  The laser treatment was completed in 12 patients. In the first group at 180 days postoperatively we did not find corneal opacities, anterior chamber or lens opacities. Pupil diameter and reactivity, endothelial cell density, and IOP were normal. Pachymetry showed an average reduction of the central corneal thickness of 99 microns (+/- 14.7 SD). Topography showed an average reduction of the corneal dioptric power of 2 D (+/- 0.4 SD). In the second group at 120 days postoperatively findings were similar. Pachymetry showed an average reduction of the central corneal thickness of 118.5 mu (+/- 12.5 SD). Topography showed an average reduction of the corneal dioptric power of 2.4D (+/- 0.9 SD).
  
  
  CONCLUSIONS
  It is possible to change the corneal power by reducing the corneal thickness with the Nd:YLF laser but the predictability of the result is unknown. Because Bowman's layer is intact, there is no scarring or haze.
authors.affiliation: Catholic University of Rome Columbus Hospital, Department of Ophthalmology, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Marchi
authors.forename: A
authors.initials: A
authors.lastname: Gualano
authors.forename: G
authors.initials: G
authors.lastname: Zumbo
authors.forename: S
authors.initials: S
authors.lastname: Marchi
mesh_terms: D003319:Corneal Stroma / Q000601:surgery*; D004869:Equipment Safety; D005500:Follow-Up Studies; D006801:Humans; D054018:Lasers, Excimer; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000295:instrumentation*; D012029:Refraction, Ocular; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology