1. The Norwegian School of Veterinary Science, Department of Small Animal Clinical Sciences, P.O. Box 8146 Dep., N-0033 Oslo, Norway.
2. Department of Morphology, Genetics and Aquatic Biology.
3. The University of North Carolina, Department of Ophthalmology, School of Medicine, CB # 7040, 617 Clinical Sciences Building, Chapel Hill, NC 27599–7040, USA