1. From the Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania;
2. Department of Ophthalmology and Visual Sciences, University of Iowa Carver College of Medicine, Iowa City, Iowa;
3. Department of Small Animal Clinical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada;
4. Department of Ophthalmology and Visual Sciences, University of Iowa Carver College of Medicine, Iowa City, Iowa;4Howard Hughes Medical Institute, Iowa City, Iowa; and
5. J.A. Baker Institute for Animal Health, Cornell University, Ithaca, New York.