title: Sequential ablation approach to the correction of mixed astigmatism.
abstract: OBJECTIVE
  To evaluate the safety, efficacy, and stability of LASIK, using positive cylinder and negative sphere nomograms in sequence (sequential ablation) to correct mixed astigmatism.
  
  
  METHODS
  This prospective study included 40 eyes of 20 patients with mixed astigmatism. Patients underwent bilateral sequential ablation LASIK using the Technolas 217 excimer laser (Bausch & Lomb Surgical, Rochester, NY). The main outcome measures, uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), were evaluated 3 and 12 months after surgery.
  
  
  RESULTS
  Preoperative astigmatism ranged from +1.75 to +6.00 diopters (D) and negative sphere from -0.50 to -3.00 D. The postoperative refraction at 3 months remained unchanged at 1 year postoperative in all patients. A total of 32 (80%) eyes showed no significant residual astigmatism (<0.50 D); the remaining 8 (20%) eyes had 0.50 to 1.00 D of residual astigmatism. Residual negative sphere was present in 2 eyes of 2 patients with a planned monovision target. In the remaining 38 (95%) eyes, no significant residual negative sphere was present. Sixteen (40%) eyes had one line of improvement in BSCVA. No eye lost lines of visual acuity. The efficacy index shows that uncorrected vision after surgery is equal or better than corrected vision before surgery. Less corneal tissue is removed and fewer laser spots are required compared to other techniques for the correction of mixed astigmatism.
  
  
  CONCLUSIONS
  The sequential ablation approach to the correction of mixed astigmatism was efficacious, safe, and stable 1 year after surgery.
authors.affiliation: Istituto Laser Microchirurgia Oculare, Brescia, Italy. pinelli@ilmo.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Pinelli
authors.forename: Elvis Nchuinang
authors.initials: EN
authors.lastname: Ngassa
authors.forename: Elena
authors.initials: E
authors.lastname: Scaffidi
mesh_terms: D000328:Adult; D000368:Aged; D001251:Astigmatism / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D003315:Cornea / Q000473:pathology* / Q000601:surgery; D019781:Corneal Topography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012029:Refraction, Ocular; D012720:Severity of Illness Index; D016896:Treatment Outcome; D014792:Visual Acuity