Visual degeneration can occur due to different causes, e.g. aging, eye injury, adaptations to the changes in the environment or even alteration in genetics. In this chapter, 6 species of vertebrates are chosen to demonstrate the characteristic degenerative changes in their retinae. The black moore goldfish, which is one of the lower vertebrates that has been reported with severe visual degeneration; and the Royal College of Surgeon rats (RCS rats), which are the frequently used genetic model for the study of degenerative changes in the retina, are included in this chapter. The other examples illustrated are Asian house shrew, Anderson’s shrew and human. Their degeneration of retinae is caused respectively by the environmental factors and aging. In the last part of this chapter, degeneration of the retina of ICR mice after receiving chronic administration of ketamine is shown. In humans, some of the most frequently encountered pathological changes of the retina are also included to introduce the readers to these common conditions.
Keywords: Goldfish, RCS rat, shrew, degeneration, retina, cystic formation, cell death, merging of inner and outer nuclear layers, invasion of pigment cells, last cones, scanning electron microscopy, light microscopy.