Ultrasound, Dacryocystorhinography and Morphological Examination of Normal Eye and Lacrimal Apparatus of the Donkey (Equus asinus)

SIMPLE SUMMARY: The role of the eye with lacrimal apparatus as a vital organ of the donkey’s body still needs to be emphasized. The lacrimal gland (LG) is anatomically located at the dorsolateral aspect of the orbit within the lacrimal fossa, and responsible for secretion of the aqueous portion of precorneal tear film. Tears are drained to the exterior through the nasolacrimal duct (NLD), which starts from two puncta lacrimalis at the medial canthus and opens into nasolacrimal sac, and ends by the nasolacrimal orifice (NLO) at the nostril of both sides. Congenital or acquired obstruction of this duct frequently occurs in horses and leads to epiphora. Therefore, the aim of the present study was to investigate the normal macromorphological and ultrasonographic features of the eye and lacrimal gland, as well as normal dacryocystorhinography of the donkey (Equus asinus) in Egypt. The results illustrated the ultrasonographic biometric values of the eye, as well as the shape and size of the lacrimal gland. In addition, dacryocystorhinography and normal dissecting anatomy of the lacrimal apparatus was illustrated. The results of this study may act as the baseline for proper management of conditions of the eye and lacrimal apparatus in the donkey in the future. ABSTRACT: The study investigated normal macromorphological and ultrasonographic features of the eye and lacrimal gland, as well as normal dacryocystorhinography of the donkey (Equus asinus) in Egypt. A total of 36 donkeys of different ages, weights, and sexes were included in the study: 21 live animals for ultrasonography and dacryocystorhinography, and 15 cadaver skulls for morphological anatomy of the lacrimal apparatus. The ultrasound biometric values of the eye were 33.7 ± 1.7 mm for axial globe length (AGL), 39.8 ± 2.1 mm for globe diameter (GD), 10.8 ± 0.7 mm for lens thickness (LT), 3.2 ± 0.7 mm for anterior chamber depth (ACD), and 19.3 ± 1.6 mm for vitreous chamber depth (VCD). The lacrimal gland was recognized as a hypoechogenic structure with an anechoic core, located at the dorsolateral aspect of the orbit, and ovoid in shape. The mean NLD length was 193.0 ± 9.8 mm by radiography and 206.0 ± 20.4 mm by gross assessment. One NL orifice (NLO) was noticed on each side, with a diameter of 3.0 ± 0.1 mm and located 12.1 ± 2.1 mm from the dorsal commissure of the nostril. These results may act as the baseline for proper management of conditions of the eye and lacrimal apparatus in the donkey in the future.