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The posterior segment is the back five-sixths [8] of the eye that includes the anterior hyaloid membrane and all of the optical structures behind it: the vitreous humor, retina, choroid, and optic nerve. [12] The radii of the anterior and posterior sections are 8 mm and 12 mm, respectively. The point of junction is called the limbus.
The thickness of the sclera varies from 1 mm at the posterior pole to 0.3 mm just behind the insertions of the four rectus muscles. The sclera's blood vessels are mainly on the surface. Along with the vessels of the conjunctiva (which is a thin layer covering the sclera), those in the episclera render the inflamed eye bright red. [6]
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] It is composed of non-keratinized, stratified squamous epithelium with goblet cells, stratified columnar epithelium and stratified cuboidal epithelium (depending on the ...
Dalrymple's sign is a widened palpebral (eyelid) opening, or eyelid spasm, seen in thyrotoxicosis (as seen in Graves' disease, exophthalmic goitre and other hyperthyroid conditions), causing abnormal wideness of the palpebral fissure.
Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera due to high bilirubin levels. [3] [6] Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme metabolism, liver dysfunction, or biliary-tract obstruction. [7]
Evisceration – removal of the iris, lens, and internal eye contents, but with the sclera and attached extraocular muscles left behind; Enucleation of the eye – removal of the eyeball, but with the eyelids and adjacent structures of the eye socket remaining. An intraocular tumor excision requires an enucleation, not an evisceration.
Eye color outside of the iris may also be symptomatic of disease. Yellowing of the sclera (the "whites of the eyes") is associated with jaundice, [82] and may be symptomatic of liver diseases such as cirrhosis or hepatitis. [83] A blue coloration of the sclera may also be symptomatic of disease. [82]
If the eyelids are open for a few hours after death, a film of cell debris and mucus forms two yellow triangles on the sclera, each at side of the iris, with base towards the margin of cornea and apex towards medial or lateral canthus of the eye, which becomes brown and then black within a few hours, upon which dust settles and the surface ...