title: Clinical results using the Holladay 2 intraocular lens power formula.
abstract: OBJECTIVE
  To analyze the accuracy of the Holladay 2 formula, which has been proposed as an improvement over the original Holladay formula.
  
  
  METHODS
  This retrospective analysis comprised 317 eyes operated on by 1 surgeon using 1 technique and 1 intraocular lens style in a specialty practice. Because the Holladay 2 formula has yet to be published, its accuracy can only be analyzed using the commercially available Holladay IOL Consultant computer program to compare it to the Holladay 1, Hoffer Q, and SRK/T formulas. Defined axial length ranges were analyzed individually.
  
  
  RESULTS
  A lower mean absolute error (MAE) trend was found for the average length eye (22.0 to 24.5 mm) by the Holladay 1 and Hoffer Q formulas. For short eyes (< 22.0 mm), the Hoffer Q and Holladay 2 perform better. The SRK/T consistently showed a trend toward the lowest MAE in all long eyes (>24.5 mm) as well as the subdivisions of medium long (24.5 to 26.0 mm) and very long (>26.0 mm). The Holladay 2 trended toward the least accurate (MAE) of the 4 formulas in all ranges of axial length except the shortest and the very longest. It appears to perform poorer in average and medium long eyes.
  
  
  CONCLUSIONS
  Although the Holladay 2 formula has improved its MAE accuracy in short eyes, it was not more accurate than the Hoffer Q. The changes made in the formula to effect this improvement in MAE seem to have sacrificed the accuracy of the original Holladay formula in eyes with average and medium long axial lengths.
authors.affiliation: University of California, Los Angeles, USA. KHofferMD@AOL.com
authors.forename: K J
authors.initials: KJ
authors.lastname: Hoffer
mesh_terms: D003315:Cornea / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D007910:Lenses, Intraocular; D008433:Mathematics; D055095:Optics and Photonics; D011474:Prosthesis Design; D012029:Refraction, Ocular; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012984:Software; D014792:Visual Acuity