title: Novel Placido-derived Topography-guided Excimer Corneal Normalization With Cyclorotation Adjustment: Enhanced Athens Protocol for Keratoconus.
abstract: OBJECTIVE
  To comparatively investigate the efficacy of the enhanced Athens Protocol procedure guided by novel Placido-derived topography with cyclorotation compensation (the cyclorotation adjusted group) to similar cases guided by Scheimpflug-derived tomography without cyclorotation compensation (the non-cyclorotation adjusted group).
  
  
  METHODS
  Two groups were evaluated: the cyclorotation adjusted group (n = 110 eyes) and the non-cyclorotation adjusted group (n = 110 eyes). Analysis was based on digital processing of Scheimpflug imaging derived curvature difference maps preoperatively and 3 months postoperatively. The vector (r, ϑ) corresponding to the steepest corneal point (cone) on the preoperative surgical planning map (rp, ϑp) and on the curvature difference map (rd, ϑd) were computed. The differences between the peak topographic angular data (Δϑ = |ϑp - ϑd|) and weighted angular difference (WΔϑ = Δϑ × Δr) were calculated.
  
  
  RESULTS
  For the cyclorotation adjusted group, Δϑ was 7.18° ± 7.53° (range: 0° to 34) and WΔϑ was 3.43 ± 4.76 mm (range: 0.00 to 21.41 mm). For the non-cyclorotation adjusted group, Δϑ was 14.50° ± 12.65° (range: 0° to 49°) and WΔϑ was 10.23 ± 15.15 mm (range: 0.00 to 80.56 mm). The cyclorotation adjusted group appeared superior to the non-cyclorotation adjusted group, in both the smaller average angular difference between attempted to achieved irregular curvature normalization and in weighted angular difference, by a statistically significant margin (Δϑ: P = .0058; WΔϑ: P = .015).
  
  
  CONCLUSIONS
  This study suggests that employment of the novel Placido-derived topographic data of highly irregular corneas, such as in keratoconus, treated with topography-guided profile with cyclorotation compensation leads to markedly improved cornea normalization.
authors.forename: Anastasios John
authors.initials: AJ
authors.lastname: Kanellopoulos
authors.forename: George
authors.initials: G
authors.lastname: Asimellis
mesh_terms: D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000378:metabolism; D003131:Combined Modality Therapy; D003319:Corneal Stroma / Q000378:metabolism; D019781:Corneal Topography / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000188:drug therapy / Q000378:metabolism / Q000601:surgery / Q000628:therapy*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D010778:Photochemotherapy / Q000379:methods; D018903:Photorefractive Keratectomy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use; D012189:Retrospective Studies; D012256:Riboflavin / Q000627:therapeutic use; D025321:Surgery, Computer-Assisted; D014466:Ultraviolet Rays; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
chemical_list: D017319:Photosensitizing Agents; D003094:Collagen; D012256:Riboflavin