title: Treatment of corneal surface irregularities using biomask as an adjunct to excimer laser phototherapeutic keratectomy.
abstract: OBJECTIVE
  To assess the clinical changes induced by the use of BioMask as an adjunct to phototherapeutic keratectomy (PTK) using the excimer laser.
  
  
  METHODS
  A nonrandomized, prospective clinical trial was conducted. Twenty-two consecutive patients were enrolled for BioMask treatment with reduced visual acuity caused by irregular astigmatism or corneal scarring. Patients were treated with a broad-beam excimer laser using the standard PTK mode. The BioMask collagen material was applied as a liquid at 47 degrees C and molded using custom-made, rigid, gas-permeable contact lenses. After allowing the material to cool for approximately 3 minutes, the lens was removed and the gel was ablated at a fluence of 130-140 mJ/cm2 at a frequency of 10 Hz, until the stromal bed appeared smooth. After surgery, patients were followed at day 1, week 1, and months 1, 3, 6, 9, and 12. The main outcome measures were best spectacle-corrected visual acuity (BSCVA) and uncorrected visual acuity (UVA).
  
  
  RESULTS
  Comparison of the preoperative and postoperative BSCVAs showed a statistically significant change in vision (p = 0.0356). Before surgery, the mean Snellen BSCVA was 20/90, whereas after surgery, BSCVA increased to 20/60. Sixty-five percent of the patients had an improved BSCVA, with an average gain of 3.7 lines per patient (range, +2 to +10). Fifteen percent of the patients lost an average of 3.0 lines (range, -2 to -6), and 20% had no change. UVA averaged 20/180 before surgery and 20/123 after surgery, but the change was not statistically significant. With respect to UVA, 63% improved by an average of 4.25 lines per patient (range, +2 to +9). Twenty-six percent (26%) lost an average of 5.6 lines (range, -2 to -8), and 10% had no change. The average follow-up time was 8 months for both BSCVA and UVA. When patients were stratified by their treatment indications and ranked in order of BSCVA outcome, patients with Salzmann's nodular degeneration did the best, followed by those with prior refractive surgery, corneal dystrophies, and corneal scars. Even though BSCVA did not improve as much in the corneal scar group, 50% of the patients reported an improvement in the symptoms they experienced before surgery based on questionnaires. Conclusion. BioMask appears to have potential as an ablatable mask material when used in conjunction with PTK for the treatment of corneal surface irregularities.
authors.affiliation: Kremer Laser Eye Center, King of Prussia, PA 19406, USA.
authors.forename: Fred
authors.initials: F
authors.lastname: Kremer
authors.forename: Michael
authors.initials: M
authors.lastname: Aronsky
authors.forename: Barry
authors.initials: B
authors.lastname: Bowyer
authors.forename: Scott X
authors.initials: SX
authors.lastname: Stevens
mesh_terms: D001251:Astigmatism / Q000601:surgery*; D001672:Biocompatible Materials; D024042:Collagen Type I / Q000627:therapeutic use; D003315:Cornea / Q000601:surgery*; D019781:Corneal Topography; D006801:Humans; D054018:Lasers, Excimer; D018903:Photorefractive Keratectomy / Q000295:instrumentation*; D011446:Prospective Studies; D016896:Treatment Outcome; D014792:Visual Acuity
chemical_list: D001672:Biocompatible Materials; D024042:Collagen Type I