title: Accuracy of Scheimpflug corneal power measurements for intraocular lens power calculation.
abstract: OBJECTIVE
  To evaluate the accuracy of corneal power measurements by the Pentacam Scheimpflug system for intraocular lens (IOL) power calculation.
  
  
  METHODS
  Studio Oculistico d'Azeglio, Bologna, Italy.
  
  
  METHODS
  Consecutive patients having phacoemulsification and in-the-bag IOL implantation were prospectively studied. Intraocular lens power was calculated by entering 3 combinations of data into the Hoffer Q formula: (1) corneal power measurements by corneal topography (simulated keratometry) and axial length (AL) measurements by Ultrascan ultrasound (US) immersion biometry; (2) Scheimpflug corneal power measurements (simulated keratometry) and US AL measurements; (3) corneal power and AL measurements by partial coherence interferometry (PCI) (IOLMaster). The prediction error was calculated as the difference between the predicted and the measured refraction 1 month postoperatively.
  
  
  RESULTS
  Forty-one eyes were evaluated. The mean arithmetic error was zero for all combinations of measurements due to constant optimization. The mean absolute error (MAE) of the Scheimpflug-US combination was good (0.44 diopters [D] +/- 0.30 [SD]) but significantly higher than the topography-US combination and PCI (0.33 +/- 0.29 D and 0.33 +/- 0.23 D, respectively) (P = .043). The percentage of eyes with an MAE of 0.75 D or greater was higher with the Scheimpflug-US combination (7 eyes, 17%) than with the corneal topography-US combination (2 eyes, 4.8%) or PCI (3 eyes, 7.3%).
  
  
  CONCLUSIONS
  Corneal power measurements with the Pentacam Scheimpflug system should be used in IOL power calculation formulas with caution because the accuracy is good but is not as high as with standard measurement methods.
authors: G.B. Bietti Eye Foundation-IRCCS, Rome, Italy. giacomo.savini@alice.it
authors: Giacomo
authors: G
authors: Savini
authors: Piero
authors: P
authors: Barboni
authors: Michele
authors: M
authors: Carbonelli
authors: Kenneth J
authors: KJ
authors: Hoffer
mesh_terms: D000368:Aged; D001699:Biometry / Q000379:methods; D003315:Cornea / Q000502:physiology*; D019781:Corneal Topography; D005123:Eye / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D018918:Phacoemulsification; D010781:Photography / Q000592:standards*; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology*; D015203:Reproducibility of Results; D014463:Ultrasonography