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The sclera, like the cornea, contains a basal endothelium, above which there is the lamina fusca, containing a high count of pigment cells. [ 6 ] Sometimes, very small gray-blue spots can appear on the sclera, a harmless condition called scleral melanocytosis.
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.
Usually unilateral, flat, patchy, pigmented area that involves the limbus (the border of the cornea and sclera) and interpalpebral (between the eyelids) conjunctiva. [5] Slit-lamp examination. Histopathological examination that shows intraepithelial proliferation of conjunctival epithelial melanocytes. [1]
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]
Uveitis (/ ˌ juː v i. aɪ t ɪ s /) is inflammation of the uvea, the pigmented layer of the eye between the inner retina and the outer fibrous layer composed of the sclera and cornea. [1] The uvea consists of the middle layer of pigmented vascular structures of the eye and includes the iris, ciliary body, and choroid.
The irises of human eyes exhibit a wide spectrum of colours. Eye color is a polygenic phenotypic trait determined by two factors: the pigmentation of the eye's iris [1] [2] and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris.
Unlike other primates, all human beings have eyes with a distinct colour contrast between the white sclera, the coloured iris, and the black pupil. This is due to a lack of pigment in the sclera. Other primates mostly have pigmented sclerae that are brown or dark in colour. There is also a higher contrast between human skin, sclera, and irises.
The pigmented retina is formed by rods and cones and composed of small cilia typical of the ependymal epithelium of the neural tube. Some cells in the lens vesicle will be fated to form the cornea and the lens vesicle will develop completely to form the definitive lens. Iris is formed from the optic cup cells.