Lijun Zhang1, Mary Ellen Sy1, Harry Mai1, Fei Yu1, D Rex Hamilton2. 1. From the Refractive Center (Zhang), 3rd Hospital of Dalian, Dalian, China; American Eye Center (Sy), Makati City, Philippines; Jules Stein Eye Institute, David Geffen School of Medicine at UCLA (Mai), the Department of Biostatistics (Yu), UCLA Fielding School of Public Health, and the UCLA Laser Refractive Center (Hamilton), Los Angeles, California, USA. 2. From the Refractive Center (Zhang), 3rd Hospital of Dalian, Dalian, China; American Eye Center (Sy), Makati City, Philippines; Jules Stein Eye Institute, David Geffen School of Medicine at UCLA (Mai), the Department of Biostatistics (Yu), UCLA Fielding School of Public Health, and the UCLA Laser Refractive Center (Hamilton), Los Angeles, California, USA. Electronic address: hamilton@jsei.ucla.edu.
Abstract
PURPOSE: To compare the prediction error after toric intraocular lens (IOL) (Acrysof IQ) implantation using corneal astigmatism measurements obtained with an IOLMaster automated keratometer and a Galilei dual rotating camera Scheimpflug-Placido tomographer. SETTING: Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, USA. DESIGN: Retrospective case series. METHODS: The predicted residual astigmatism after toric IOL implantation was calculated using preoperative astigmatism values from an automated keratometer and the total corneal power (TCP) determined by ray tracing through the measured anterior and posterior corneal surfaces using dual Scheimpflug-Placido tomography. The prediction error was calculated as the difference between the predicted astigmatism and the manifest astigmatism at least 1 month postoperatively. The calculations included vector analysis. RESULTS: The study evaluated 35 eyes (35 patients). The preoperative corneal posterior astigmatism mean magnitude was 0.33 diopter (D) ± 0.16 (SD) (vector mean 0.23 × 176). Twenty-six eyes (74.3%) had with-the-rule (WTR) posterior astigmatism. The postoperative manifest refractive astigmatism mean magnitude was 0.38 ± 0.18 D (vector mean 0.26 × 171). There was no statistically significant difference in the mean magnitude prediction error between the automated keratometer and TCP techniques. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect against-the-rule (ATR) astigmatism. The TCP technique lacked these biases. CONCLUSIONS: The automated keratometer and TCP methods for estimating the magnitude of corneal astigmatism gave similar results. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect ATR astigmatism. FINANCIAL DISCLOSURE: Dr. Hamilton has received honoraria for educational lectures from Ziemer Ophthalmic Systems. No other author has a financial or proprietary interest in any material or method mentioned.
PURPOSE: To compare the prediction error after toric intraocular lens (IOL) (Acrysof IQ) implantation using corneal astigmatism measurements obtained with an IOLMaster automated keratometer and a Galilei dual rotating camera Scheimpflug-Placido tomographer. SETTING: Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, USA. DESIGN: Retrospective case series. METHODS: The predicted residual astigmatism after toric IOL implantation was calculated using preoperative astigmatism values from an automated keratometer and the total corneal power (TCP) determined by ray tracing through the measured anterior and posterior corneal surfaces using dual Scheimpflug-Placido tomography. The prediction error was calculated as the difference between the predicted astigmatism and the manifest astigmatism at least 1 month postoperatively. The calculations included vector analysis. RESULTS: The study evaluated 35 eyes (35 patients). The preoperative corneal posterior astigmatism mean magnitude was 0.33 diopter (D) ± 0.16 (SD) (vector mean 0.23 × 176). Twenty-six eyes (74.3%) had with-the-rule (WTR) posterior astigmatism. The postoperative manifest refractive astigmatism mean magnitude was 0.38 ± 0.18 D (vector mean 0.26 × 171). There was no statistically significant difference in the mean magnitude prediction error between the automated keratometer and TCP techniques. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect against-the-rule (ATR) astigmatism. The TCP technique lacked these biases. CONCLUSIONS: The automated keratometer and TCP methods for estimating the magnitude of corneal astigmatism gave similar results. However, the automated keratometer method tended to overcorrect WTR astigmatism and undercorrect ATR astigmatism. FINANCIAL DISCLOSURE: Dr. Hamilton has received honoraria for educational lectures from Ziemer Ophthalmic Systems. No other author has a financial or proprietary interest in any material or method mentioned.
Authors: Sepehr Feizi; Siamak Delfazayebaher; Mohammad Ali Javadi; Farid Karimian; Vahid Ownagh; Fatemeh Sadeghpour Journal: J Ophthalmic Vis Res Date: 2018 Apr-Jun