Ocular melanosis
Encyclopedia
Ocular melanosis also known as ocular melanocytosis or melanosis oculi, is a congenital disease of the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

 which affects about 1 in every 5000 people and is a risk factor for uveal melanoma
Uveal melanoma
Uveal melanoma is a cancer of the eye involving the iris, ciliary body, or choroid . Tumors arise from the pigment cells that reside within the uvea giving color to the eye...

. In dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

s is found almost exclusively in the Cairn Terrier
Cairn Terrier
The Cairn Terrier is the oldest of the terrier breeds, originating in the Scottish Highlands and recognized as one of Scotland's earliest working dogs...

, where until recently it was known as pigmentary glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...

 (see also canine glaucoma
Canine glaucoma
Glaucoma in dogs refers to a group of diseases that affect the optic nerve and involves a loss of retinal ganglion cells in a characteristic pattern. Raised intraocular pressure is a significant risk factor for developing glaucoma...

). The disease is caused by an increase of melanocyte
Melanocyte
-External links: - "Eye: fovea, RPE" - "Integument: pigmented skin"...

s in the iris
Iris (anatomy)
The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina. "Eye color" is the color of the iris, which can be green, blue, or brown. In some cases it can be hazel , grey, violet, or even pink...

, choroid
Choroid
The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye , while in the outlying areas it narrows to 0.1 mm...

, and surrounding structures. Overproduction of pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

 by these cells can block the trabecular meshwork
Trabecular meshwork
The trabecular meshwork is an area of tissue in the eye located around the base of the cornea, near the ciliary body, and is responsible for draining the aqueous humor from the eye via the anterior chamber .The tissue is spongy and lined by trabeculocytes; it allows fluid to drain into a set of...

 through which fluid drains from the eye. The increased fluid in the eye leads to increased pressure, which can lead to glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...

. In humans, this is sometimes known as pigment dispersion syndrome
Pigment dispersion syndrome
Pigment dispersion syndrome is an affliction of the eye that can lead to a form of glaucoma known as pigmentary glaucoma. It takes place when pigment cells slough off from the back of the iris and float around in the aqueous humor...

.

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