Accuracy of corneal power measurements by a new Scheimpflug camera combined with Placido-disk corneal topography for intraocular lens power calculation in unoperated eyes. 2012

Giacomo Savini, and Piero Barboni, and Michele Carbonelli, and Kenneth J Hoffer
G.B. Bietti Eye Foundation-IRCCS, Rome, Italy. giacomo.savini@alice.it

OBJECTIVE To assess the accuracy of the corneal power measurements with a new Scheimpflug camera combined with Placido-disk corneal topography (Sirius) (combined Scheimpflug camera-topographer) for intraocular lens (IOL) power calculation in unoperated eyes and compare the results with those by a validated corneal topographer (Keratron) (validated topographer). METHODS Private practice. METHODS Case series. METHODS Consecutive patients having phacoemulsification and in-the-bag IOL implantation were studied. Intraocular lens power was calculated using the Hoffer Q, Holladay 1, and SRK/T formulas; the axial length, as measured by ultrasound immersion biometry; and 3 corneal power measurements: validated topographer simulated keratometry (K); combined Scheimpflug camera-topographer simulated K (derived from anterior corneal curvature only); combined Scheimpflug camera-topographer mean pupil power (derived from anterior and posterior corneal curvatures through ray tracing). The prediction error was calculated as the difference between the predicted refraction and the refraction measured 1 month postoperatively. RESULTS When the corneal power measurements from the combined Scheimpflug camera-topographer were used, the mean absolute error (MAE) ranged between 0.23 diopter (D) ± 0.24 (SD) (simulated K and Hoffer Q formula) and 0.33 ± 0.23 D (mean pupil power and SRK/T formula). There were no statistically significant differences between the MAE generated by the simulated Ks of the 2 devices with any of the 3 formulas. CONCLUSIONS Both corneal power measurements (simulated K and mean pupil power) provided by the new combined Scheimpflug camera-topographer were successfully entered into third-generation IOL power calculation formulas in unoperated eyes. BACKGROUND Dr. Hoffer is the author of the Hoffer Q formula and owns the EyeLab, which sells Hoffer Programs. No other author has a financial or proprietary interest in any material or method mentioned.

UI MeSH Term Description Entries
D007910 Lenses, Intraocular Artificial implanted lenses. Implantable Contact Lens,Lens, Intraocular,Contact Lens, Implantable,Intraocular Lens,Intraocular Lenses,Lens, Implantable Contact
D008297 Male Males
D010781 Photography Method of making images on a sensitized surface by exposure to light or other radiant energy. Photographies
D011446 Prospective Studies Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group. Prospective Study,Studies, Prospective,Study, Prospective
D012029 Refraction, Ocular Refraction of LIGHT effected by the media of the EYE. Ocular Refraction,Ocular Refractions,Refractions, Ocular
D003315 Cornea The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous CORNEAL EPITHELIUM; BOWMAN MEMBRANE; CORNEAL STROMA; DESCEMET MEMBRANE; and mesenchymal CORNEAL ENDOTHELIUM. It serves as the first refracting medium of the eye. It is structurally continuous with the SCLERA, avascular, receiving its nourishment by permeation through spaces between the lamellae, and is innervated by the ophthalmic division of the TRIGEMINAL NERVE via the ciliary nerves and those of the surrounding conjunctiva which together form plexuses. (Cline et al., Dictionary of Visual Science, 4th ed) Corneas
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000368 Aged A person 65 years of age or older. For a person older than 79 years, AGED, 80 AND OVER is available. Elderly
D001699 Biometry The use of statistical and mathematical methods to analyze biological observations and phenomena. Biometric Analysis,Biometrics,Analyses, Biometric,Analysis, Biometric,Biometric Analyses

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