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The stroma around the iris sphincter muscle becomes darker than the peripheral stroma. [medical citation needed] A stimulation of melanin synthesis within iris melanocytes has been postulated. [21] Neoplasm – Nevi and melanomatous tumors. Iridocorneal endothelium syndrome [3] Iris ectropion syndrome [3] [22]
Choroidal nevus (plural: nevi) is a type of eye neoplasm that is classified under choroidal tumors as a type of benign (non-cancerous) melanocytic tumor. [1] A choroidal nevus can be described as an unambiguous pigmented blue or green-gray choroidal lesion, found at the front of the eye, around the iris, [2] or the rear end of the eye.
In humans, the pigmentation of the iris varies from light brown to black, depending on the concentration of melanin in the iris pigment epithelium (located on the back of the iris), the melanin content within the iris stroma (located at the front of the iris), and the cellular density of the stroma. [4]
BCEM, also referred to as conjunctival hypermelanosis, complexion-associated melanosis, or racial melanosis, is a non-cancerous lesion of the conjunctiva that is more commonly found in dark-skinned individuals (over 90% of lesions are found in black persons and around 5% in white persons). [1]
Melanin is a compound found in plants, animals, and protists, and is derived from the amino acid tyrosine. Melanin is a photoprotectant, absorbing the DNA-damaging ultraviolet radiation of the sun. Vertebrates have melanin in their skin and hair, feathers, or scales.
Aniridia is the absence of the iris, a muscular structure that opens and closes the pupil to allow light into the eye. It is also responsible for eye color. Without it, the central eye appears all black. It can be congenital, in which both eyes are usually involved, or caused by a penetrant injury. [1]
Many forms of hyperpigmentation are caused by an excess production of melanin. [4] Hyperpigmentation can be diffuse or focal, affecting such areas as the face and the back of the hands. Melanin is produced by melanocytes at the lower layer of the epidermis. Melanin is a class of pigment responsible for producing color in the body in places such ...
A gingival melanin index in 4 degrees was established. [5] Already with a consumption of 1-3 cigarettes a day 9.3% of all 20.333 examined showed a smoker's melanosis. Pipe smokers had smoker's melanosis in 16.8%. One year after the start of cigarette smoking a clinically visible smoker's melanosis could be seen in 12.3% of women, and 17% among men.