title: Intraocular lens power calculation for humanitarian missions based on partial biometry.
abstract: OBJECTIVE
  To determine whether the correlation between corneal power (K) and axial length (AL) can be used for intraocular lens (IOL) power calculation when biometric data are incomplete.
  
  
  METHODS
  Developing regions served by United States Navy humanitarian assistance missions.
  
  
  METHODS
  Case series.
  
  
  METHODS
  Measurements of K and AL were collected from all adult cataract surgery charts and used to calculate emmetropic IOL powers. A formula for estimating K or AL was derived by Deming regression analysis. The emmetropic IOL powers were calculated by hypothetical scenarios as follows: (1) K estimated from the formula and measured AL, (2) mean population K and measured AL, (3) measured K and estimated AL, and (4) measured K and mean population AL. The mean absolute refractive error (MAE) was calculated for each hypothetical scenario and an additional scenario (scenario 5) using single IOL power for all eyes. The MAEs were compared with a paired t test.
  
  
  RESULTS
  The formula derived from Deming regression analysis was K = 74.56 - 1.317 × AL. The MAE for the scenarios were (1) 0.90 diopters (D), (2) 1.11 D, (3) 1.91 D, (4) 1.55 D, and (5) 1.22 D. The MAE for scenario 1 was significantly less (P<.01) than that for scenarios 2 and 5. The MAE for scenario 5 was significantly less than that for scenarios 3 and 4.
  
  
  CONCLUSIONS
  The correlation between K and AL can be used to improve accuracy of IOL calculation when K is unavailable. When the AL is unavailable, the mean population IOL power is most accurate.
  
  
  BACKGROUND
  No author has a financial or proprietary interest in any material or method mentioned.
authors.affiliation: Ophthalmology Department, Naval Medical Center, Naval Medical Center San Diego, San Diego, San Diego, California 92134-2202, USA. joseph.schmitz@med.navy.mil
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Schmitz
authors.forename: Kimberly D
authors.initials: KD
authors.lastname: Davis
authors.forename: Scott K
authors.initials: SK
authors.lastname: McClatchey
mesh_terms: D000328:Adult; D000533:Altruism; D058452:Axial Length, Eye; D001699:Biometry / Q000379:methods*; D003315:Cornea / Q000502:physiology; D003906:Developing Countries; D058453:Emmetropia / Q000502:physiology; D006801:Humans; D007910:Lenses, Intraocular; D008493:Medical Missions; D008887:Military Medicine / Q000458:organization & administration; D055095:Optics and Photonics; D012029:Refraction, Ocular / Q000502:physiology; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology