Posters

Evaluation of Corvis ST and ocular response analyzer indices changes after laser refractive surgery

Poster Details

First Author: M. Sedaghat IRAN, ISLAMIC REPUBLIC OF

Co Author(s):    A. Omidtabrizi   A. Vahedi   M. Shafiee   N. Morovatdar           

Abstract Details

Purpose:

To investigate corneal biomechanic changes by evaluating Corvis ST and Ocular Response Analyzer (ORA) parameters after laser vision correction (LVC).

Setting:

This was a prospective cohort study conducted in eye research center, faculty of medicine, Mashhad University of Medical Sciences.

Methods:

Eighty six eyes were studied in 2 groups; group 1: individuals undergoing PRK (144 eyes), and group 2: individuals undergoing femtosecond assisted LASIK (24 eyes). ORA and Corvis ST measurements were performed by an experienced technician before and 4 months after LVC.

Results:

Multivariate analysis showed that corneal thickness , intraocular pressure and mean keratometric power have confounding effect on Corvis ST and ORA parameters (P=0.00). After adjustment for ablation depth, first applanation time, second applanation time, time of highest concavity and peak distance showed a significant change independently to the type of surgery; although the change was more remarkable in PRK group. Corneal Hysteresis (CH) and Corneal Resistance Factor (CRF) in ORA decreased significantly (P=0.38 and P=0.017, respectively). Intraocular pressure (IOP) didn’t change significantly in Corvis ST and ORA (P=0.452 and P=0.407, respectively).

Conclusions:

Corneal deformation in response to air puff occurs faster and reverses slower after LVC. ORA and to some extent Corvis measurements suggest reduction of corneal resistance after LVC. Although not significant, Lasik eyes show less change in Corvis and ORA parameters 4 months post-operatively. ORA and Corvis IOP measurement are reliable after LVC.

Financial Disclosure:

NONE