1. Department of Veterinary Medicine; Federal University of Paraná; Curitiba PR Brazil
2. Rua dos Funcionários; 1540, Laboratório de Oftalmologia Comparada; Hospital Veterinário; Curitiba PR 80035-050 Brazil
3. Small Animal Clinical Sciences; Michigan State University; D-208, Veterinary Medical Center; East Lansing MI 48824-1314 USA