title: Accuracy of intraocular lens power calculations in eyes with axial length <22.00 mm.
abstract: BACKGROUND
  To assess the accuracy of Haigis, Holladay 1, Hoffer Q and SRK/T formulae in eyes with axial length of <22.00 mm.
  
  
  METHODS
  Retrospective comparative analysis.
  
  
  METHODS
  163 eyes of 97 patients undergoing phacoemulsification and intraocular lens (IOL) implantation.
  
  
  METHODS
  Ocular biometry was performed using IOLMaster laser interferometry. Predicted refractive outcomes before and after lens constant adjustment were compared to actual refractive outcomes.
  
  
  METHODS
  Mean prediction (ME) and mean absolute errors (MAE) with standard deviations (±SD).
  
  
  RESULTS
  Mean preoperative spherical equivalent was +5.44D ± 1.97D. Mean axial length was 21.20 mm ± 0.60 mm. Using standard IOL constants the MAE for Hoffer Q (0.62D, ±0.52D) and Holladay 1 (0.66D ± 0.52D) were significantly lower than SRK/T (MAE 0.91D ± 0.64D; P = <0.0005 and P = 0.001 respectively), but not Haigis (MAE 0.82D ± 0.83D, P = 0.071 and 0.22 respectively). MAEs for all formulae were significantly reduced by IOL constant adjustment (all P = <0.001). Following this there was no statistically significant difference in MAEs between formulae (range 0.50-0.57D, P = 0.57). Increasing MAE was significantly associated with reducing axial length and increasing IOL power for all formulae. For bilateral cases, prediction errors between eyes were significantly correlated across all formulae (all P = <0.0001) and explained 32-42% of the variance in prediction error between eyes.
  
  
  CONCLUSIONS
  Prediction of postoperative refraction in patients with short axial lengths is challenging and at the limit of current, popular IOL formulae. There is now a clear need for prospective studies to assess latest generation IOL formulae such as Holladay 2 or Olsen in small eyes.
authors.affiliation: UCL Institute of Ophthalmology, London, UK. alex.day@ucl.ac.uk
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Day
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Foster
authors.forename: Julian D
authors.initials: JD
authors.lastname: Stevens
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058452:Axial Length, Eye / Q000002:abnormalities*; D001699:Biometry; D005260:Female; D006801:Humans; D007368:Interferometry; D007834:Lasers; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D055095:Optics and Photonics; D018918:Phacoemulsification; D012029:Refraction, Ocular / Q000502:physiology; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014792:Visual Acuity / Q000502:physiology