Effect of transepithelial photorefractive keratectomy on myopic eyes: visual quality and main factors predicting it

Session Details

Session Title: Surface Ablations for Correction of Ammetropias

Session Date/Time: Tuesday 16/09/2014 | 08:00-10:30

Paper Time: 08:18

Venue: Auditorium

First Author: : S.Adib Moghaddam IRAN

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

Abstract Details

Purpose:

To investigate visual quality outcomes (Photopic(P) and Mesopic(M) contrast sensitivity(CS)) of myopic patients undergoing trans-epithelial photorefractive keratectomy as well as surgical and preoperative visual parameters predicting it.

Setting:

Bina Eye Hospital, Tehran, Iran

Methods:

96 eyes (51 patients) with pure myopia or mixed myopic astigmatism were recruited in a prospective study from July 2011 to September 2013. All of the cases underwent Trans-PRK by same expert refractive surgeon (S.A.M.) using SCHWIND AMARIS 500 laser (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). Follow-up visits were scheduled for 6, 9 and 18 months post-operation. Pre-op and post-op visits visual acuity, refraction, CS, keratometry indices and high order aberrations (HOA) were registered. In our contrast sensitivity assessment system, the lower values indicate better CS. Paired t-test was used to assess CS change by operation. Hosmer and Lemeshow analysis approach was used to investigate pure effect of different surgical (optical zone, transitional zone, ablation depth,…) and visual parameters (visual acuity, refraction, keratometry, pupil diameter, HOAs,…) on post-op PCS and MCS. Finally developed models were assessed for Heteroscedasticity and collinearity issues.

Results:

PCS and MCS improved significantly from pre-op values of 0.96 (0.85 - 1.07) and 1.21 (0.97 - 1.46) to 0.82 (0.71-0.94) and 0.96 (0.81 - 1.12) at least 6 months after the operation with paired t-test P.values of 0.0015 and 0.0020, respectively. According to linear regression models with highest goodness of fit developed for post-op PCS following main predictors were generated: pre-op PCS (coefficient: 0.12 deteriorating, P < 0.001), transition zone (coefficient: 0.27 deteriorating, P < 0.001), optical zone (coefficient: 0.3 improving, P < 0.001) and post-op coma aberration (coefficient: 0.3 deteriorating, P < 0.001). Corresponding model for post-op MCS denoted that post-op PCS (coefficient: 0.94 deteriorating, P < 0.001), ablation zone (coefficient: 0.15 improving, P = 0.017), transition zone (coefficient: 0.13 deteriorating, P = 0.047) and pupil diameter (coefficient: 0.004 deteriorating, P = 0.001) were main independent predictors.

Conclusions:

Myopia correction by trans-PRK significantly improves MCS and PCS. Larger optical zone improves while larger transitional zone and higher post-op coma aberration deteriorates post-op PCS. Larger ablation zone improves while larger transitional zone, pupil diameter and worse post-op PCS deteriorate post-op MCS

Financial Interest:

NONE