![]() ![]() ![]() Accessory visual structures include the lacrimal gland and the eyelid. The eyeball lies within the bony orbit, which has several openings for the passage of neurovascular structures. Cranial nerves mediate vision ( CN II) and eye movement ( CN III, IV, VI), while accommodation is mediated by fibers of the autonomic nervous system. The eye receives its arterial supply from branches of the ophthalmic artery and drains into the ophthalmic vein. ![]() The refractive media, comprising the cornea, lens, aqueous humor, and vitreous body, directs and refracts light to the posterior region of the retina. The visual pathway begins with the first-order neurons of the retina, retinal rods and cones, which convert the optical image into neuronal signals, which are transmitted to the brain. Functionally, the eye can be divided into structures that perceive light (components of the visual pathway) and structures that refract light (refractive media). The anterior eye is subdivided further into two chambers: the posterior chamber (between lens and iris) and the anterior chamber (between iris and cornea), both of which are filled with aqueous humor. The lens is suspended between the pupil and the vitreous body by ligaments attached to the ciliary body. The eye is further divided into an anterior segment, which contains the lens and structures anterior to it, and a posterior segment, which contains the vitreous humor and the retina. Anatomically, the outer portion of the eye is divided into three layers: the fibrous tunic ( cornea and sclera), the vascular tunic ( choroid, iris, and ciliary body), and the nervous tunic ( retina). The eyes are paired, sensory organs that enable vision. ![]()
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