1. Institute of Veterinary Clinical Science, School of Veterinary Medicine, National Taiwan University, Taipei 106, Taiwan
2. Department of Ophthalmology, National Taiwan University Veterinary Hospital, Taipei 106, Taiwan
3. School of Medicine, Fu-Jen Catholic University, New Taipei City 242, Taiwan
4. College of Veterinary Medicine, Ohio State University, OH 43210, U.S.A.