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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.
Diagram showing the position of the pecten oculi within a bird eye. The pecten or pecten oculi is a comb-like structure of blood vessels belonging to the choroid in the eye of a bird. It is a non-sensory, pigmented structure that projects into the vitreous humor from the point where the optic nerve enters the eyeball. [1]
The iris (pl.: irides or irises) is a thin, annular structure in the eye in most mammals and birds that is responsible for controlling the diameter and size of the pupil, and thus the amount of light reaching the retina. In optical terms, the pupil is the eye's aperture, while the iris is the diaphragm. Eye color is defined by the iris.
Birds have acute eyesight—raptors (birds of prey) have vision eight times sharper than humans—thanks to higher densities of photoreceptors in the retina (up to 1,000,000 per square mm in Buteos, compared to 200,000 for humans), a high number of neurons in the optic nerves, a second set of eye muscles not found in other animals, and, in some ...
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 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 ...
How can you tell if they’re safe past their expiration dates? Here, doctors explain how long most vitamins last and any risks associated with taking expired vitamins.
In ornithology, the lore is the region between the eye and bill on the side of a bird's head. [1] This region is sometimes featherless, and the skin may be tinted, as in many species of the cormorant family. [2] This area, which is directly in front of the eye, features a "loral stripe" in many bird species including the red-capped plover.