title: Comparison of Tear cytokines and clinical outcomes between off-flap and on-flap epi-LASIK with mitomycin C.
abstract: OBJECTIVE
  To compare tear cytokines and clinical outcomes between off-flap and on-flap epi-LASIK eyes and explore the possible mechanism for the clinical differences.
  
  
  METHODS
  This double-masked, randomized study enrolled 18 myopic patients who underwent off-flap epi-LASIK with mitomycin C (MMC) in 1 eye and on-flap epi-LASIK with MMC in the contralateral eye. Tears were collected from each eye preoperatively and 2 hours, 1 day, and 5 days postoperatively. Concentrations of multiple tear cytokines were measured by a multiplex immunobead assay. Uncorrected distance visual acuity (UDVA), refraction, haze scores, pain scores, and percentage of corneal epithelial healing were evaluated.
  
  
  RESULTS
  Compared with the on-flap group, the off-flap group had outcomes of better UDVA and higher percentages of epithelial healing at 5 days after surgery (P<.001) and lower levels of haze at 1 month after surgery (P=.049). Preoperatively, no significant differences were noted in the release rate of all tear cytokines between groups. At 2 hours postoperatively, the release rate of tear basic fibroblast growth factor (bFGF), platelet-derived growth factor-BB (PDGF-BB), interleukin-8 (IL-8), and tumor necrosis factor alpha (TNF-α) in the off-flap group were significantly lower than those in the on-flap group (P=.011, .017, .048, and .041, respectively).
  
  
  CONCLUSIONS
  Off-flap epi-LASIK with MMC offers faster corneal epithelial healing and visual recovery, and temporary less haze than on-flap epi-LASIK with MMC. The lower tear levels of bFGF, PDGF-BB, IL-8, and TNF-α in the offflap group 2 hours after surgery may suggest a possible mechanism for the clinical differences.
authors.affiliation: Department of Ophthalmology, Peking University Third Hospital, Beijing, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yue-Guo
authors.initials: YG
authors.lastname: Chen
authors.forename: Ying-Jie
authors.initials: YJ
authors.lastname: Xia
authors.forename: Hong
authors.initials: H
authors.lastname: Qi
mesh_terms: D000328:Adult; D000477:Alkylating Agents / Q000008:administration & dosage*; D003131:Combined Modality Therapy; D016207:Cytokines / Q000378:metabolism*; D004311:Double-Blind Method; D058447:Eye Pain / Q000503:physiopathology; D005136:Eye Proteins / Q000378:metabolism; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007118:Immunoassay; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D016685:Mitomycin / Q000008:administration & dosage*; D009216:Myopia / Q000503:physiopathology / Q000601:surgery; D010147:Pain Measurement; D012029:Refraction, Ocular / Q000502:physiology; D013524:Surgical Flaps; D013666:Tears / Q000378:metabolism*; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D014945:Wound Healing / Q000502:physiology; D055815:Young Adult
chemical_list: D000477:Alkylating Agents; D016207:Cytokines; D005136:Eye Proteins; C042434:tear proteins; D016685:Mitomycin