Image Enhancement Methods for a Customized Videokeratography System Designed for Animals with Small Eyes

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

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Image Enhancement Methods for a Customized Videokeratography System Designed for Animals with Small Eyes Bin Chen, Shan Ling, Hongfei Cen, Wenfu Xu, Kee Chea-su, Yongjin Zhou and Lei Wang Abstract 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 B. Chen  S. Ling  Y. Zhou (&)  L. Wang Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, People’s Republic of China e-mail: [email protected] B. Chen  W. Xu Harbin Institute of Technology Shenzhen Graduate School, Shenzhen, People’s Republic of China S. Ling School of Geosciences and Info-Physics, Central South University, Changsha, People’s Republic of China H. Cen Peking University Shenzhen Hospital, Shenzhen 518036, People’s Republic of China K. Chea-su School of Optometry, Hong Kong Polytechnic University, Hong Kong, People’s Republic of China Y. Zhou  L. Wang The Shenzhen Key Laboratory for Low-cost Healthcare, Shenzhen, People’s Republic of China Y. Zhou Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, People’s Republic of China

S. Li et al. (eds.), Frontier and Future Development of Information Technology 1001 in Medicine and Education, Lecture Notes in Electrical Engineering 269, DOI: 10.1007/978-94-007-7618-0_98,  Springer Science+Business Media Dordrecht 2014

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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. Keywords Videokeratography filtering

 Gabor filtering  Multiscale vessel enhancement

98.1 Introduction The study of human corneal surface topography is usually predicated on the study of animal cornea surface topography model. Previous researches [1–3] showed that almost all the astigmatism of animals that induced by sphericity and astigmatic lens are corneal-originated, and more detailed information of cornea should be provided to make further study of astigmatism mechanism. Generally, static measurements for corneal surface topography could be evaluated based on a Placido disc pattern in the image data obtained using videokeratography Sys