title: Corneal changes following collagen cross linking and simultaneous topography guided photoablation with collagen cross linking for keratoconus.
abstract: OBJECTIVE
  To compare the outcome of Collagen cross-linking (CXL) with that following topography-guided customized ablation treatment (T-CAT) with simultaneous CXL in eyes with progressive keratoconus.
  
  
  METHODS
  This was a prospective, non-randomized single centre study of 66 eyes with progressive keratoconus. Of these, 40 eyes underwent CXL and 26 eyes underwent T-CAT + CXL. The refractive, topographic, tomographic and aberrometric changes measured at baseline, 1, 3 and 6 months post-operatively were compared between both groups.
  
  
  RESULTS
  After a mean follow-up of 7.7 ± 1.3 months, the mean retinoscopic cylinder decreased by 1.02 ± 3.16 D in the CXL group ( P = 0.1) and 2.87 ± 3.22 D in the T-CAT + CXL group ( P = 0.04). The Best corrected visual acuity increased by 2 lines or more in 10% of eyes in the CXL group and in 23.3% of eyes in the T-CAT + CXL group. The mean steepest-K reduced by 0.40 ± 3.71 D ( P = 0.77) in the CXL group and by 2.91 ± 2.01D ( P = 0.03) in the T-CAT + CXL group. The sag factor and surface asymmetry index showed no significant change in the CXL group but reduced by 3.59 ± 5.94 D ( P = 0.01) and 0.72 ± 1.18 ( P = 0.02) respectively in the T-CAT + CXL group. There was a significant increase in the highest posterior corneal elevation in both groups (9.57 ± 14.93 μ in the CXL group and 7.85 ± 9.25 μ in the T-CAT + CXL group, P ≤ 0.001 for both). There was significantly greater reduction of mean coma ( P < 0.001) and mean higher-order aberrations ( P = 0.01) following T-CAT + CXL compared to CXL.
  
  
  CONCLUSIONS
  CAT + CXL is an effective approach to confer biomechanical stability and to improve the corneal contour in eyes with keratoconus and results in better refractive, topographic and aberrometric outcomes than CXL alone.
authors.affiliation: Department of Cornea and Refractive Surgery, Medical Research Foundation, Sankara Nethralaya, Chennai, Tamil Nadu, India.
authors.forename: Prema
authors.initials: P
authors.lastname: Padmanabhan
authors.forename: Aishwaryah
authors.initials: A
authors.lastname: Radhakrishnan
authors.forename: Abinaya Priya
authors.initials: AP
authors.lastname: Venkataraman
authors.forename: Nidhi
authors.initials: N
authors.lastname: Gupta
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Srinivasan
mesh_terms: D000293:Adolescent; D000328:Adult; D003094:Collagen / Q000378:metabolism*; D003315:Cornea / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D019781:Corneal Topography / Q000379:methods*; D003432:Cross-Linking Reagents / Q000627:therapeutic use*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D053685:Laser Therapy / Q000379:methods*; D008297:Male; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011446:Prospective Studies; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014792:Visual Acuity; D055815:Young Adult
chemical_list: D003432:Cross-Linking Reagents; D017319:Photosensitizing Agents; D003094:Collagen