Magnetic Resonance Imaging and Cross-Sectional Anatomy of the Eye and the Optic Nerve in the Egyptian Donkey (Equus asinus)

The eye is a high sense organ which is susceptible to many infectious and traumatic diseases. Using an accurate diagnostic imaging technique became essential for early detection and control of these diseases. The current investigation is proposed to fully describe the normal magnetic resonance imaging (MRI) appearance of the eye, extraocular structures and the optic nerve in the donkey with the aid of the anatomical sections. Eight fresh cadaveric heads of adult donkeys of both sexes were used; two were scanned using an MRI scanner of 1.5 Tesla magnet, and six were frozen to be sectioned into transverse (n=3) and frontal (n=3) sections. The accessed MR images were serially selected in matching to their corresponding gross sections. These MR images provided a comprehensive assessment of the eyeball structures (choroid, ciliary body, iris, cornea, sclera, anterior and posterior chambers, and vitreous body), the ocular adnexa (upper, lower and third eyelids, lacrimal gland, tarsal gland, superficial gland of the third eyelid, extraocular muscles and orbital fat), the various parts of the optic nerve (intraocular, intraorbital, intracanalicular, intracranial) and its surrounding meningeal sheath complex. However, it was difficult to outline the retina. The current investigation administrated a precise anatomical atlas of the eye, periorbital structures and optic nerve in the donkey assisting in the interpretation and diagnosis of both ocular diseases and optic neuropathy.