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Effect of trans-epithelial photorefractive keratectomy on myopic eyes higher order aberrations and main factors predicting it

Poster Details

First Author: S.Adib Moghaddam IRAN

Co Author(s):    S. Soleyman-Jahi   F. Adili Aghdam                 

Abstract Details


To investigate higher order aberrations of myopic eyes undergoing trans-epithelial photorefractive keratectomy and surgical and preoperative visual parameters predicting it.


TransPRK research group, Bina Eye Hospital, Tehran, Iran, from December 2012 to May 2014.


125 eyes (72 patients) with myopia±astigmatism were recruited in a prospective study. All of the cases underwent Trans-PRK by the same expert refractive surgeon (S.A.M.) using AMARIS 500 laser (SCHWIND, Kleinostheim, Germany). Patients had at least three months of follow up. Pre-op and post-op visits visual acuity, refraction, Contrast sensitivity, keratometry indices and corneal wave front (CWF) and ocular wave front (OWF) higher order aberrations (HOA) were registered. Hosmer and Lemeshow analysis approach was used to investigate pure effect of different surgical and visual parameters on post-op HAOs. Finally developed models were assessed for Heteroscedasticity and collinearity issues.


CWF coma and spherical aberrations significantly improved; tetrafoil and secondary astigmatism were slightly induced. OWF spherical aberration improved and coma aberration did not change. In multivariate analysis for CWF spherical aberration improvement, preoperative astigmatism (adjusted coefficient (AC)=0.03(0.01-0.05),P =0.012), transitional zone (AC=0.03(0.01-0.11),P =0.012) and pupil diameter >4mm (AC=0.03(0.01-0.05),P =0.010) were independent inducers; optical zone (AC=0.08(0.04-0.13),P <0.001) was independent improving determinant. Multivariate model revealed that only pupil diameter >4mm independently predicts OWF coma induction (AC=0.14(0.04-0.25),P=0.01) and optical zone (AC=0.58(0.20-0.97),P=0.04), K1(AC=0.18 (0.07-0.28),P=0.003) and preoperative CDVA (AC=0.37(0.11 – 0.63),P=0.01) significantly predict aberration improvement. For CWF coma change merely transitional zone was independent inducer (AC=0.04(0.01-0.08),P=0.01).


Myopia correction by trans-PRK significantly improves CWF coma and spherical aberration and OWF spherical aberration. Clinically notable changes were not detected in other parameters. Larger optical zone improves HOAs while larger transitional zone and pupil diameter induces HOAs.

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