Factors associated with changes in posterior corneal surface following photorefractive keratectomy

Session Details

Session Title: Presented Poster Session: Refractive Surgery New Techniques/Instrumentation/Devices II

Venue: Poster Village: Pod 2

First Author: : A.Nemet ISRAEL

Co Author(s): :    M. Mimouni   I. Vainer   T. Sela   G. Munzer   I. Kaiserman           

Abstract Details

Purpose:

To identify factors associated with changes in the posterior cornea curvature following laser refractive surgery.

Setting:

Care-Vision Laser Centers, Tel-Aviv, Israel

Methods:

This retrospective study included myopic astigmatic eyes that underwent PRK between January 2013 and December 2013 at Care-Vision Laser Centers, Tel-Aviv, Israel. The average posterior K was measured with the Sirius device at a radius of 3 millimeters from the center. The surgical induced change in the average posterior k was calculated. The correlation between change in posterior K and parameters such as preoperative central corneal thickness (CCT) and refraction, Baiocchi Calossi Versaci index (BCV), ablation depth, percent of tissue ablated (PTA) and residual stroma bed (RSB) was analyzed.

Results:

A total of 280 eyes with a mean age of 24.9± 6.1 years(range,18-47 years were included in this study.The mean PTA was 14.8 ±6.0%.A lower CCT (r=-0.24,p<0.001),higher myopia(r=-0.34,p<0.001),increased astigmatism (r=-0.17,p<0.001),increased total BCV(r=0.13,p=0.03),decreased back BCV(r=-0.12,p=0.05),increased front BCV(r=0.16,p=0.01),increased posterior I-S ratio(r=0.16, p=0.01)and a lower RSB(r=-0.42,p<0.001)were all significantly correlated with percentage of change in mean posterior K A greater change in posterior K was found in females(p=0.01)smaller optic zones of 6.0mm(p=0.02)and PTA > 20%(p<0.001).In ranked stepwise multiple regression,26.2% of the variance of change in posterior K could be explained by the examined factors.The factors that remained significant were PTA(p<0.001),CCT(p=0.001) and posterior I-S ratio(p=0.001).

Conclusions:

Preoperative CCT, posterior I-S ratio and PTA are significantly associated with increase in posterior K after PRK. Understanding of factors affecting a change in posterior cornea after refractive surgery may be important practical value for the prevention of iatrogenic keratectasia.

Financial Disclosure:

None