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The bony area that makes up the human eye socket provides exceptional protection to the sclera. However, if the sclera is ruptured by a blunt force or is penetrated by a sharp object, the recovery of full former vision is usually rare. If pressure is applied slowly, the eye is actually very elastic.
The upper eyelid crease is a common variation between people of White and East Asian ethnicities. [9] Westerners commonly perceive the East Asian upper eyelid as a "single eyelid". [9] However, East Asian eyelids are divided into three types – single, low, and double – based on the presence or position of the lid crease. [10]
The eyes sit in bony cavities called the orbits, in the skull. There are six extraocular muscles that control eye movements. The front visible part of the eye is made up of the whitish sclera, a coloured iris, and the pupil. A thin layer called the conjunctiva sits on top of this. The front part is also called the anterior segment of the eye.
Image of a human eye showing the blood vessels of the bulbar conjunctiva Hyperaemia of the superficial bulbar conjunctiva blood vessels. In the anatomy of the eye, the conjunctiva (pl.: conjunctivae) is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). [1]
The word ciliary had its origins around 1685–1695. [17] The term cilia originated a few years later in 1705–1715, and is the Neo-Latin plural of cilium meaning eyelash . In Latin , cilia means upper eyelid and is perhaps a back formation from supercilium , meaning eyebrow .
The skin thus drawn upon is thrown into folds, especially radiating from the lateral angle of the eyelids; these folds become permanent in senescence, and form the so-called "crow's feet". The Levator palpebræ superioris is the direct antagonist of this muscle; it raises the upper eyelid and exposes the front of the bulb of the eye. In ...
The neuropsychological side of visual information processing is known as visual perception, an abnormality of which is called visual impairment, and a complete absence of which is called blindness. The visual system also has several non-image forming visual functions, independent of visual perception, including the pupillary light reflex and ...
The levator palpebrae superioris receives motor innervation from the superior division of the oculomotor nerve. [1] [2] [3] The smooth muscle that originates from its undersurface, called the superior tarsal muscle is innervated by postganglionic sympathetic axons from the superior cervical ganglion.