ABSENCE OR PRESENCE OF TAPETUM LUCIDUM: MACRO AND MICROSCOPIC INVESTIGATIONS IN DONKEY (EQUUS ASINUS), CAT (FELIS DOMESTICA) AND ONE-HUMPED CAMEL (CAMELUS DROMEDARIUS)

For explanation eye-shine phenomenon, we used both eyes of five healthy adult donkeys (Equus asinus), cats (Felis domestica) and one-humped camels (Camelus dromedarius). The eyes of a live animal of the three species were photographed under existing light and with a flash. The donkey's pupils appeared black centrally situated and horizontal in direction at daylight. Under flash, the light condensed centrally and the color changed to green or blue. The cat's pupils were oval vertically slit-like and colored yellow to red orange under flash. The camel's pupils characterized by presence of a small centrally spot of light with flash. Tapetum of the donkey was horizontal triangular in shape under the weak light colored indigo with dark blue spots changed into semicircular appearance under strong light. In the cat, Tapetum appeared semicircular in outline with yellow color under weak and strong light. The fundus of camel appeared divided into dark proximal half and lighter distal one under the weak light. Under flash, the two halves appeared transparent white. Microscopically, Tapetum lucidum of the donkey was fibrous in its texture while in cat, it was cellular. In camel, there was a brush's membrane and no Tapetum lucidum. In donkey, the thickness of the tapetal tissue and the degree of pigmentation in the retinal epithelium differed according to the region of Tapetum. The thick tapetal tissue and the unpigmented retinal epithelium combination created the greater reflectance of light. So the absence or presence of Tapetum, the tapetal tissue thickness, the degree of pigmentation in the retinal epithelium and the degree of illumination controlled the eye-shine phenomenon.