Accuracy of Scheimpflug corneal power measurements for intraocular lens power calculation
Received 9 January 2009; received in revised form 16 February 2009; accepted 17 February 2009.
Refers to erratum:
Errata
Journal of Cataract & Refractive Surgery
August 2009 (Vol. 35, Issue 8, Page 1483) Full Text |
Full-Text PDF (67 KB)
Purpose
To evaluate the accuracy of corneal power measurements by the Pentacam Scheimpflug system for intraocular lens (IOL) power calculation.
Setting
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%).
Conclusion
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.
From the G.B. Bietti Eye Foundation-IRCCS (Savini), Rome, and Studio Oculistico d'Azeglio (Barboni, Carbonelli), Bologna, Italy; Jules Stein Eye Institute (Hoffer), University of California, Los Angeles, California, USA
Dr. Hoffer is the author of the Hoffer Q formula and owns The EyeLab, which sells the Hoffer Programs database. No other author has a financial or proprietary interest in any material or method mentioned.
ABSTRACT