Morphology of retinal photoreceptor layer in continuous light-exposed and dark-adapted male cats

The morphology of retinal photoreceptor layer was studied in continuous light-exposed and dark-adapted domestic male cats (Felis catus). The eyes of 12 healthy adult cats (4 in continuous light-exposed group, 4 in continuous dark-adapted group, and 4 in control group) were routinely fixed and studied by electron microscope. Results showed that the general structure of photoreceptor layer in this animal was the same as other species; rods were elongated and slender cells. Cone photoreceptors were shorter and stouter than rod photoreceptors. Cats exposed to continuous light for 24 hrs showed increased numbers of melanosome in retinal epithelial layer. The outer segments of rods and cones were long. Vacuoles increased the extracellular space and some condensed nuclei were observed in the inner segments. Continuous dark-adapted group showed a few melanosomes. In this group, the extracellular space, large swelling and condensed nuclei were more than those in other groups.