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Anatomy of the avian eye. The main structures of the bird eye are similar to those of other vertebrates.The outer layer of the eye consists of the transparent cornea at the front, and two layers of sclera — a tough white collagen fibre layer which surrounds the rest of the eye and supports and protects the eye as a whole.
The outer border of the iris does not change size. The constricting muscle is located on the inner border. The back surface is covered by a heavily pigmented epithelial layer that is two cells thick (the iris pigment epithelium), but the front surface has no epithelium. This anterior surface projects as the dilator muscles.
The nictitating membrane of a masked lapwing as it closes over the left eye, originating from the medial canthus. The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision.
The globe of the eye, or bulbus oculi, is the frontmost sensory organ of the human ocular system, going from the cornea at the front, to the anterior part of the optic nerve at the back. More simply, the eyeball itself, as well as the ganglion cells in the retina that eventually transmit visual signals through the optic nerve. [1]
The ring is in the fibrous outer layer of the eye, called the sclera. The structure is commonly referred to as the sclerotic ring; but, because the word sclerotic often implies pathology of the sclera ( see " sclerosis ", an unrelated medical condition [ 2 ] ), recent authors have urged avoiding the use of this term, to avoid confusion and to ...
The sclera, [note 1] also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective outer layer of the eye containing mainly collagen and some crucial elastic fiber. [2] In the development of the embryo, the sclera is derived from the neural crest. [3]
The retina (from Latin rete 'net'; pl. retinae or retinas) is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs.The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception.
The episclera is the outermost layer of the sclera (the white of the eye). [1] It is composed of loose, fibrous, elastic tissue and attaches to Tenon's capsule. [1]A vascular plexus is found between the bulbar conjunctiva and the sclera consisting of two layers of vessels, the superficial episcleral vessels and the deep episcleral vessels.