title: Clinical effect of blowing nitrogen gas across the cornea during photorefractive keratectomy.
abstract: OBJECTIVE
  We evaluated the clinical effects of blowing nitrogen gas over the cornea during photorefractive keratectomy.
  
  
  METHODS
  We retrospectively compared clinical outcomes of 32 patients (37 eyes), divided into two groups who had photorefractive keratectomy with nitrogen gas blowing across the cornea (n = 19) and without nitrogen gas (n = 18). All photorefractive keratectomies were performed between April 1991 and August 1992. Ablation zone diameters were 5.0 or 5.5 mm. The average attempted correction was -3.47 +/- 1.76 diopters (D) in the nitrogen gas group, and -3.48 +/- 1.25 D in the non-nitrogen gas group.
  
  
  RESULTS
  The nitrogen gas group achieved more accurate corrections than the non-nitrogen gas group, but had a significantly greater amount of corneal haze at all postoperative examinations. Corneal haze was most evident at 1 month and gradually diminished therafter in both groups. At 6 months, videokeratography revealed a central island in 2 eyes (11.1%) of the non-nitrogen gas group. Because of undercorrection (2 eyes) or central island (1 eye), 3 out of 18 eyes in the non-nitrogen gas group were reablated 6 months later.
  
  
  CONCLUSIONS
  The non-nitrogen gas group had more undercorrections and a higher frequency rate of central steep islands, but nitrogen gas blowing caused a greater amount of corneal haze.
authors.affiliation: Department of Ophthalmology, University of Rochester Medical Center, New York, USA.
authors.forename: M
authors.initials: M
authors.lastname: Itoi
authors.forename: R
authors.initials: R
authors.lastname: Ryan
authors.forename: M
authors.initials: M
authors.lastname: Depaolis
authors.forename: J V
authors.initials: JV
authors.lastname: Aquavella
mesh_terms: D000287:Administration, Topical; D000328:Adult; D003131:Combined Modality Therapy; D003315:Cornea / Q000187:drug effects* / Q000503:physiopathology / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D054018:Lasers, Excimer; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D009584:Nitrogen / Q000008:administration & dosage*; D009887:Ophthalmoscopy; D018903:Photorefractive Keratectomy / Q000379:methods*; D012044:Regression Analysis; D012189:Retrospective Studies; D016896:Treatment Outcome; D014792:Visual Acuity
chemical_list: D009584:Nitrogen