title: Ray-tracing intraocular lens power calculation using anterior segment optical coherence tomography measurements.
abstract: OBJECTIVE
  To assess the efficiency of ray-tracing intraocular lens (IOL) power calculation with anterior segment optical coherence tomography (AS-OCT) in normal eyes with cataract.
  
  
  METHODS
  Miyata Eye Hospital, Miyakonojo, Miyazaki, Japan.
  
  
  METHODS
  Case series.
  
  
  METHODS
  The study comprised consecutive patients who had cataract surgery and obtained a corrected visual acuity of 0.15 logMAR or better postoperatively. Preoperatively, Placido topography and AS-OCT measurements were taken during a routine examination. The predicted postoperative refractions were obtained using 3 methods: the SRK/T formula with autokeratometry, ray-tracing calculation with Placido topography data, and ray-tracing calculations with AS-OCT measurement of both corneal surfaces. The refractive errors from the manifest refraction spherical equivalent were compared 1 month postoperatively, and the effects of corneal eccentricity and posterior corneal curvature were evaluated.
  
  
  RESULTS
  Seventy patients (102 eyes) were enrolled. There was no significant difference in refractive errors (P=.89). The refractive error with the SRK/T formula was correlated significantly with corneal eccentricity (P=.0017); the ray-tracing calculations were unaffected. There was a weak correlation with the posterior corneal curvature in the ray-tracing calculations performed with Placido topography (P<.0002).
  
  
  CONCLUSIONS
  The accuracy of the ray-tracing IOL power calculations using AS-OCT data was comparable to that of the conventional formula and minimized the effect of corneal eccentricity and posterior corneal curvature.
authors.affiliation: Miyata Eye Hospital, Miyakonojo, Miyazaki, Japan. minami@miyata-med.ne.jp
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Minami
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kataoka
authors.forename: Jiro
authors.initials: J
authors.lastname: Matsunaga
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Ohtani
authors.forename: Masato
authors.initials: M
authors.lastname: Honbou
authors.forename: Kazunori
authors.initials: K
authors.lastname: Miyata
mesh_terms: D000328:Adult; D000368:Aged; D019781:Corneal Topography; D003867:Depth Perception / Q000502:physiology; D005260:Female; D006801:Humans; D007368:Interferometry; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D055095:Optics and Photonics; D018918:Phacoemulsification; D011446:Prospective Studies; D019591:Pseudophakia / Q000503:physiopathology; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology; D041623:Tomography, Optical Coherence / Q000379:methods*; D014792:Visual Acuity / Q000502:physiology