title: Femtosecond Laser-Assisted Intrastromal Relaxing Incisions After Penetrating Keratoplasty: Effect of Incision Depth.
abstract: OBJECTIVE
  To correlate the efficacy of femtosecond laser-assisted intrastromal relaxing incisions after penetrating keratoplasty with the posterior depth of corneal incisions.
  
  
  METHODS
  Twenty eyes of 20 patients were treated for regular postoperative penetrating keratoplasty astigmatism. Sutures had been removed and refraction had stabilized. Ultrasound pachymetry was used to calculate incisional depth. Femtosecond laser-assisted paired arcuate incisions were made inside the graft stroma, leaving 90 µm of intact anterior cornea including epithelium. The intact posterior corneal margin was 10% of the measured corneal thickness for 10 patients (10% group) and 125 µm for the remaining 10 patients (125-µm group). Follow-up visits consisted of biomicroscopy, intraocular pressure measurement, fundus examination, and topographic evaluation using anterior segment optical coherence tomography at 1 and 3 months. Postoperative corneal thickness and the depth of incisions were measured with optical coherence tomography.
  
  
  RESULTS
  Corrected distance visual acuity improved from 0.5 to 0.3 logMAR (Snellen: 20/63 to 20/40, P < .05) in the 10% group and remained constant in the 125-µm group. The refractive cylinder decreased by 34% in the 10% group (range: 0% to 60%), but did not change in the 125-µm group. The topographic anterior cylinder decreased in both groups by 48% (range: 0% to 67%) and 13% (range: 0% to 38%), respectively. The smaller the posterior intact corneal margin, the higher the surgically induced astigmatism (P < .05).
  
  
  CONCLUSIONS
  Efficacy of femtosecond laser-assisted intrastromal relaxing incisions is correlated with the posterior depth of the incisions. The deeper incisions were more effective.
authors.forename: Olli
authors.initials: O
authors.lastname: Wetterstrand
authors.forename: Juha M
authors.initials: JM
authors.lastname: Holopainen
authors.forename: Kari
authors.initials: K
authors.lastname: Krootila
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000209:etiology / Q000601:surgery*; D003316:Corneal Diseases / Q000601:surgery; D063171:Corneal Pachymetry; D003319:Corneal Stroma / Q000601:surgery*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D015948:Keratoplasty, Penetrating; D053685:Laser Therapy / Q000379:methods*; D008297:Male; D033401:Microscopy, Acoustic; D008875:Middle Aged; D011183:Postoperative Complications; D012029:Refraction, Ocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology