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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 homozygous mutation causes prenatal onset of recurrent fractures of the ribs and long bones, demineralization, decreased ossification of the skull, and blue sclerae; it is clinically type II or type III. [77] Family members who are heterozygous for OI XVI may have recurrent fractures, osteopenia and blue sclerae. [77] [78]
The uvea (/ ˈ j uː v i ə /; [1] derived from Latin: uva meaning "grape"), also called the uveal layer, uveal coat, uveal tract, vascular tunic or vascular layer, is the pigmented middle layer of the three concentric layers that make up an eye, precisely between the inner retina and the outer fibrous layer composed of the sclera and cornea.
Blue eyes are also found in southern Europe, Central Asia, South Asia, North Africa and West Asia. [58] [59] Approximately 8% to 10% of the global population have blue eyes. [35] A 2002 study found that the prevalence of blue eye color among the white population in the United States to be 33.8% for those born from 1936 through 1951.
Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or one blue eye and one brown eye), a white forelock or patches of light skin.
Eye color is an inherited trait determined by multiple genes. [14] [15] These genes are sought by studying small changes in the genes themselves and in neighboring genes, called single-nucleotide polymorphisms or SNPs.
Episcleritis may be differentiated from scleritis by using phenylephrine or neosynephrine eye drops, which causes blanching of the blood vessels in episcleritis, but not in scleritis. [3] A blue color to the sclera suggests scleritis, rather than episcleritis.
Ocular melanosis (OM) is a blue-gray and/or brown lesion of the conjunctiva that can be separated into benign conjunctival epithelial melanosis (BCEM) and primary acquired melanosis (PAM), of which the latter is considered a risk factor for uveal melanoma. [1]