Algorithm for Correcting the Keratometric Error in the Estimation of the Corneal Power in Eyes With Previous Myopic Laser Refractive Surgery

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Title: Algorithm for Correcting the Keratometric Error in the Estimation of the Corneal Power in Eyes With Previous Myopic Laser Refractive Surgery
Authors: Camps, Vicente J. | Piñero, David P. | Mateo Pérez, Verónica | Ribera Vicent, David | Fez Saiz, Dolores de | Blanes Mompó, Francisco J. | Alzamora Rodríguez, Antonio
Research Group/s: Grupo de Óptica y Percepción Visual (GOPV)
Center, Department or Service: Universidad de Alicante. Departamento de Óptica, Farmacología y Anatomía
Keywords: LASIK | Corneal power | Scheimpflug photography | Solid-state laser | Keratometric index
Knowledge Area: Óptica
Issue Date: Nov-2013
Publisher: Lippincott, Williams & Wilkins
Citation: Cornea. 2013, 32(11): 1454-1459. doi:10.1097/ICO.0b013e31829e1eb5
Abstract: Purpose: To calculate theoretically the errors in the estimation of corneal power when using the keratometric index (nk) in eyes that underwent laser refractive surgery for the correction of myopia and to define and validate clinically an algorithm for minimizing such errors. Methods: Differences between corneal power estimation by using the classical nk and by using the Gaussian equation in eyes that underwent laser myopic refractive surgery were simulated and evaluated theoretically. Additionally, an adjusted keratometric index (nkadj) model dependent on r1c was developed for minimizing these differences. The model was validated clinically by retrospectively using the data from 32 myopic eyes [range, −1.00 to −6.00 diopters (D)] that had undergone laser in situ keratomileusis using a solid-state laser platform. The agreement between Gaussian (PGaussc) and adjusted keratometric (Pkadj) corneal powers in such eyes was evaluated. Results: It was found that overestimations of corneal power up to 3.5 D were possible for nk = 1.3375 according to our simulations. The nk value to avoid the keratometric error ranged between 1.2984 and 1.3297. The following nkadj models were obtained: nkadj= −0.0064286r1c + 1.37688 (Gullstrand eye model) and nkadj = −0.0063804r1c + 1.37806 (Le Grand). The mean difference between Pkadj and PGaussc was 0.00 D, with limits of agreement of −0.45 and +0.46 D. This difference correlated significantly with the posterior corneal radius (r = −0.94, P < 0.01). Conclusions: The use of a single nk for estimating the corneal power in eyes that underwent a laser myopic refractive surgery can lead to significant errors. These errors can be minimized by using a variable nk dependent on r1c.
ISSN: 0277-3740 (Print) | 1536-4798 (Online)
DOI: 10.1097/ICO.0b013e31829e1eb5
Language: eng
Type: info:eu-repo/semantics/article
Rights: © 2013 by Lippincott Williams & Wilkins
Peer Review: si
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Appears in Collections:INV - GOPV - Artículos de Revistas

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