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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]
Melanin (/ ˈ m ɛ l ə n ɪ n / ⓘ; from Ancient Greek μέλας (mélas) 'black, dark') is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. [1] Melanin pigments are produced in a specialized group of cells known as melanocytes.
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]
In short, melasma is a chronic skin condition that appears as darkened areas on the face due to an overproduction of melanin, says Gina Charles, MO, a family physician specializing in skincare. It ...
Pigmentary changes in the retina – In addition to the pigmented cells in the iris (the colored part of the eye), there are pigmented cells beneath the retina. As these cells break down and release their pigment, dark clumps of released pigment and later, areas that are less pigmented may appear [ citation needed ]
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]
They also have two layers of pigmented tissue in the eye: the stroma, at the front of the iris, and the iris pigment epithelium, a thin but critical layer of pigmented cells at the back of the iris. Melanin is also present in the inner ear, and is important for the early development of the auditory system. [2]
Melanin is yellowish to dark hazel in the stromal pigment cells, and black in the iris pigment epithelium, which lies in a thin but very opaque layer across the back of the iris. Most human irises also show a condensation of the brownish stromal melanin in the thin anterior border layer, which by its position has an overt influence on the ...