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Accuracy of a dual-Scheimpflug analyzer and a new optical biometer for intraocular lens power calculation in unoperated eyes

Poster Details

First Author: T.Kara Akyüz TURKEY

Co Author(s):    A. Kulak   E. Güler   Y. Totan   İ. Hepsen     

Abstract Details


To assess the accuracy and agreement of corneal power measurements provided by Galilei dual-Scheimpflug Analyzer (Zeimer Group, Port, Switzerland) and a new optical biometer Nidek AL-Scan (Nidek CO., LTD.) for intraocular lens (IOL) power calculation in unoperated eyes.


Turgut Ozal University Hospital, Ankara, Turkey


Thirty eyes of 30 patients who underwent phacoemulsification with aspheric acrylic intraocular lens (Tecnis 1-piece, ZCB00, AMO) implantation were included. Five different corneal power values were evaluated: (1) simulated keratometry (SimK; performed with the Galilei); (2) average total corneal power steep and flat meridians over a 1- to 4-mm diameter (TCP Meridian; performed with the Galilei); (3) SimK derived from anterior corneal curvature only (performed with Galilei) ; (4) mean K readings 2.4 mm zone; (performed with the AL-Scan) (5) mean K readings 3.3 mm zone (performed with the AL-Scan). The mean arithmetic error was zero for all combinations of measurements due to constant optimization. Using the SRK-T formula to determine the IOL power, predicted refractions with these five corneal powers were calculated; the prediction error was calculated as the difference between the predicted and the measured refraction 4 weeks postoperatively.


The corneal power measurements of Galilei were 43.87 ± 1.50 D for SimK, 42.90 ± 1.50 D for TCP, 43.38 ± 1.56 D for SimK anterior curvature, respectively. The corneal power measurements of Nidek AL-Scan were 44.04 ± 1.53 D for SimK (2.4 mm) and 43.97 ± 1.54 D for SimK (3.3 mm). Mean absolute prediction errors of Galilei were 0.15 ± 0.39 D for SimK, 0.20 ± 0.45 D for TCP and 0.18 ± 0.46 D for SimK anterior curvature, respectively. Regarding the Nidek AL Scan, mean absolute prediction errors were 0.12 ± 0.39 D for SimK (2.4 mm) and 0.16 ± 0.39 D for SimK (3.3 mm) (P > 0.05).


The accuracies of IOL calculation using these five different corneal power measurements were highly predictable for normal patients. Therefore, we suggest that the Galilei predicts IOL power as well as the Nidek AL-Scan for unoperated eyes. FINANCIAL INTEREST: NONE

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