Posters

Investigating the topographic effect of epithelium in myopic eyes with and without topographic preoperative abnormalities

Poster Details

First Author: I.Salah-Mabed FRANCE

Co Author(s):    A. Saad   D. Gatinel                 

Abstract Details

Purpose:

To investigate the epithelium topographic properties by comparing the epithelium (air-tear film) and the Bowman layer’s specular topographies in normal (Group N) and keratoconus suspected (Group KCS) classified corneas having low to moderate myopia corrected by photorefractive keratectomy (PRK).

Setting:

Rothschild foundation, Paris, France.

Methods:

Anterior corneal specular Placido topography using the OPD-Scan II Placido-based topograph (NIDEK, Gammagori, Japan) was performed in 97 eyes of 55 patients (Group N; 77 eyes, Group KCS; 20 eyes) undergoing PRK for myopia before and after the epithelium removal. The differences in axial keratometry, asphericity (Q value), astigmatism magnitude (toricity) and axis were computed in the first, third and fifth central corneal mm zones in both normal and keratoconus suspected corneas groups. High order aberrations have also been analyzed before and after epithelium removal and compared in the two groups.

Results:

The mean difference in axial mean keratometry and magnitude of epithelial induced astigmatism were respectively 0.52 ± 0.20 D, 0.54 ± 0.29 D x 90° (positive cylinder)and 0.48 ± 0.27 D, 0.72 ± 0.63 D x 86° respectively in normal eyes and in the KCS group. The mean difference in asphericity (on the steep axe over central 6.0 mm) was - 0.04 ± 0.25 and - 0.17 ± 0.22 respectively in normal eyes and in KCS groups. These differences were significant (p< 0.0001) for all groups. There was no significant increase in HOAs after removal of the epithelium (p< 0.05).

Conclusions:

In low to moderately myopic eyes, the topography of the Bowman layer is significantly steeper than that of the epithelium for all groups. The epithelial layer tends to reduce the magnitude of the Bowman layer’s astigmatism and prolateness.

Financial Disclosure:

None