We built a Placido’s disc videokeratographic system intended for eye examination of small animals. To derive the corneal topology and other corneal biometric parameters we rely on precise extraction of Placido ring patterns. However, since the images from CCD are noisy, image enhancement is necessary as a pre-processing procedure in order to prevent further noise magnification during the corneal surface topography reconstruction. In this study, two popular image enhancement methods, namely Gabor Filtering (GF) and Multiscale Vessel Enhancement Filtering (MVEF), are quantitatively evaluated in the context of image enhancement before corneal reconstruction. The two methods were tested on 21 images of steel balls with different diameters. Both methods have been demonstrated to be useful for Placido ring extraction; however, the GF method showed better performance on images of steel balls with smaller diameter. Compared to the GF method, the MVEF method performed better on images of steel balls with larger diameter. The result of the present work implies that the two methods should be used cooperatively.
- Gabor filtering
- Multiscale vessel enhancement filtering