title: Corneal power estimation for intraocular lens power calculation after corneal laser refractive surgery in Chinese eyes.
abstract: OBJECTIVE
  To develop and evaluate an algorithm for corneal power estimation in intraocular lens (IOL) power calculation after corneal laser refractive surgery in Chinese eyes.
  
  
  METHODS
  Guangdong Eye Institute, Guangdong Academy of Medical Sciences, Guangzhou, China.
  
  
  METHODS
  Prospective comparative case series.
  
  
  METHODS
  Corneal parameters in Chinese eyes and German eyes were measured using a rotating Scheimpflug camera. Corneal power was simplified as a corrective algorithm: K(C) = 1.114 × K(M) + K(2) (K(M) = measured K reading; K(2) = K(P) - K(A) × K(P) × CT/1.376; K(A) = anterior corneal power; K(P) = posterior corneal power; CCT = central corneal thickness). The variation and change in K(2) induced by refractive surgery were analyzed in Chinese eyes. The corrective algorithm was identified as K(C) = 1.114 × K(M) - 6.20. The method was evaluated in Chinese cataract cases after refractive surgery using the Haigis formula.
  
  
  RESULTS
  No difference in anterior corneal radius (R(A)) or CCT between Chinese eyes and German eyes were found; however, the posterior corneal radius (R(P)), R(A)/R(P) ratio, keratometric index, and K(2) were different. The mean K(2) was -6.23 diopters (D) ± 0.24 (SD) in Chinese eyes and -6.12 ± 0.23 D in German eyes (P<.01). The mean change in K(2) induced by refractive surgery was -0.02 ± 0.06 D. The median absolute prediction error in IOL power calculation was 0.43 D (range 0.01 to 1.80 D).
  
  
  CONCLUSIONS
  The algorithm was a relatively reliable method in IOL power calculation after corneal refractive surgery in Chinese eyes.
authors.affiliation: Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors.forename: Haiying
authors.initials: H
authors.lastname: Jin
authors.forename: Gerd U
authors.initials: GU
authors.lastname: Auffarth
authors.forename: Haike
authors.initials: H
authors.lastname: Guo
authors.forename: Peiquan
authors.initials: P
authors.lastname: Zhao
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D044466:Asian People / Q000208:ethnology; D001699:Biometry; D002681:China / Q000453:epidemiology; D003315:Cornea / Q000503:physiopathology*; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000208:ethnology / Q000503:physiopathology / Q000601:surgery*; D055095:Optics and Photonics; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology; D044465:White People / Q000208:ethnology; D055815:Young Adult