title: Comparative study of visual acuity and aberrations after intralase femtosecond LASIK: small corneal flap versus big corneal flap.
abstract: OBJECTIVE
  To study the effect of different flap sizes on visual acuity, refractive outcomes, and aberrations after femtosecond laser for laser in situ keratomileusis (LASIK).
  
  
  METHODS
  In each of the forty patients enrolled, 1 eye was randomly assigned to receive treatment with a 8.1mm diameter corneal flap, defined as the small flap, while the other eye was treated with a 8.6mm diameter corneal flap, defined as the big flap. Refractive errors, visual acuity, and higher-order aberrations were compared between the two groups at week 1, month 1 and 3 postoperatively.
  
  
  RESULTS
  The postoperative refractive errors and visual acuity all conformed to the intended goal. Postoperative higher-order aberrations were increased, especially in spherical aberration (Z12) and vertical coma (Z7). There were no statistically significant differences between the two groups in terms of postoperative refractive errors, visual acuity, root mean square of total HOAs (HO-RMS), trefoil 30° (Z6), vertical coma (Z7), horizontal coma (Z8), trefoil 0° (Z9), and spherical aberration (Z12) at any point during the postoperative follow-up.
  
  
  CONCLUSIONS
  Both the small and big flaps are safe and effective procedures to correct myopia, provided the exposure stroma meets the excimer laser ablations. The personalized size corneal flap is feasible, as we can design the size of corneal flap based on the principle that the corneal flap diameter should be equal to or greater than the sum of the maximum ablation diameter and apparatus error.
authors.affiliation: Department of Ophthalmology, Shandong Provincial Hospital affiliated to Shandong University, No.324 Jingwuweiqi Road, Jinan 250021, Shandong Province, China ; Department of Ophthalmology, The Second People's Hospital of Jinan, 148 Jingyi Road, Jinan 250001, Shandong Province, China.
authors.forename: Ya-Li
authors.initials: YL
authors.lastname: Zhang
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Chang-Xia
authors.initials: CX
authors.lastname: Cui
authors.forename: Ming
authors.initials: M
authors.lastname: Hu
authors.forename: Zhao-Na
authors.initials: ZN
authors.lastname: Li
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Cao
authors.forename: Xiu-Hua
authors.initials: XH
authors.lastname: Jing
authors.forename: Guo-Ying
authors.initials: GY
authors.lastname: Mu
keywords: aberration; femtosecond laser; flap; laser in situ keratomileusis; refractive surgery; visual acuity