title: [Intraocular lens calculation for cataract treated with photorefractive keratectomy using ray tracing method].
abstract: OBJECTIVE
  Conventional methods (such as the SRK-II formula) do not accurately calculate the power of the intraocular lens (IOL) after refractive surgery. Therefore, we compared a new formula including a ray tracing method to the conventional method for foldable IOL lens implantation.
  
  
  METHODS
  Foldable IOLs (MA 60 BM) were implanted in 26 patients (32 eyes) using the phakoemulsification technique. The power of the IOL was measured preoperatively using the SRK-II formula in all cases. From the results of postoperative refractive errors of these cases, the power of IOL calculated by the ray tracing method was compared to the SRK-II formula. Cataract patients first treated with photorefractive keratectomy (PRK) received IOL implants using our ray tracing method and their postoperative refraction was measured.
  
  
  RESULTS
  The average postoperative refractive error was 1.32 D in SRK-II formula, 0.95 D in the ray tracing method with Ray 1 used and 0.89 D with Ray 2 used. Postoperative refraction of both eyes first treated with PRK was--1.00 D.
  
  
  CONCLUSIONS
  The average postoperative refractive error was reduced in the ray tracing method using Olsen's predicted ACD (Ray 2) compared to SRK-II formula. This new tracing method appears to be useful for determination of IOL power and it may be applied for IOL calculation for cataract surgery after refractive surgery.
authors.affiliation: Department of Ophthalmology, Juntendo University, Urayasu Hospital, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ishikawa
authors.forename: A
authors.initials: A
authors.lastname: Hirano
authors.forename: K
authors.initials: K
authors.lastname: Murai
authors.forename: M
authors.initials: M
authors.lastname: Kumagai
authors.forename: K
authors.initials: K
authors.lastname: Nakayasu
authors.forename: A
authors.initials: A
authors.lastname: Kanai
mesh_terms: D002386:Cataract / Q000628:therapy*; D006801:Humans; D054018:Lasers, Excimer; D007910:Lenses, Intraocular; D008722:Methods; D018918:Phacoemulsification; D018903:Photorefractive Keratectomy; D012030:Refractive Errors