Morphological and bioreflecting characteristics of tapetum lucidum in dogs and cows

Abstract

Tapetum lucidum is the specially modifided, bio-reflecting tissue layer, which at most vertebrates covers the biggest part of the middle eye tunic, the chorioidea. Physiologically, the most important role of this layer is to reflect light which passes through the retina back to it, causing the secondary stimulation of the photoreceptors. In the dim light ambient conditions when the pupil is dilated, reflected beams of the light create the visual effect of the “animals' eyes shining in the dark“, while exiting the eyes. The aims of this study are to define bio-reflecting and morphological charachteristics of the tapetum lucidum in the dog and cow eyes. Because the tapetum lucidum is an adaptive structure of the eye on poorly illuminated environment, the results of our research indicate that the anatomy of the eye, particulary shape of the pupil, placement of the eyes on the animals' head, and diet, all affect the morphology and bioreflecting characteristics of this structure.