title: Mass spectrometry analysis of the by-products of intrastromal photorefractive keratectomy.
abstract: OBJECTIVE
  To determine the nature and chemical composition of the cavitation bubbles generated by intrastromal photorefractive keratectomy (IPRK) with the Neodymium: Yttrium Lithium Fluoride (Nd:YLF) picosecond laser.
  
  
  METHODS
  IPRK was performed on the corneas of three fresh human cadaver eyes with the Nd:YLF picosecond laser. High energy levels of 200 mJ/pulse to 300 mJ/pulse were used to produce the maximum amount of gas within the corneal stroma. The cavitation bubbles produced in the stroma were aspirated using a gas-tight syringe connected to a valve, and the specimens were analyzed with a mass spectrometer.
  
  
  RESULTS
  The experiment was performed on three different occasions using one cadaver eye in each experiment. The analysis consistently revealed a mixture of carbon dioxide, carbon monoxide, water vapor, oxygen, and nitrogen. Atmospheric control samples also revealed oxygen and nitrogen. No other components were detected.
  
  
  CONCLUSIONS
  The gaseous by-products of IPRK with the picosecond laser result from the simple breakdown of stromal tissue and contain no toxic or unexpected components. We found that these gaseous products are capable of rapid elimination by absorption or diffusion out of the intact cornea.
authors.affiliation: Department of Ophthalmology, New York Eye and Ear Infirmary, New York 10003, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Habib
authors.forename: M G
authors.initials: MG
authors.lastname: Speaker
authors.forename: W F
authors.initials: WF
authors.lastname: Schnatter
mesh_terms: D002102:Cadaver; D003319:Corneal Stroma / Q000737:chemistry* / Q000648:ultrastructure; D005740:Gases / Q000032:analysis*; D006801:Humans; D054018:Lasers, Excimer; D013058:Mass Spectrometry; D008855:Microscopy, Electron, Scanning; D018903:Photorefractive Keratectomy; D011184:Postoperative Period
chemical_list: D005740:Gases