Introduction:
Melanocytes are skin and eye cells that produce and retain melanin pigment. Melanocytes are neural crest-derived cells located in the lower layer of the skin epidermis (basal layer), the middle layer of the eye (uvea), and the inner ear. Melanin is the dark pigment mainly responsible for the color of the skin. Once synthesized, melanin is contained in special cell organelles called melanosomes and transported to the nearby keratin layer to induce pigmentation. Functionally, melanin acts as a UV (ultraviolet) rays protector. Melanocytes also play a role in the immune system.
What Is Ocular Melanocytosis?
Oculocutaneous melanocytosis (ODM), also known as nevus of Ota, is a congenital pigmentary defect of the periocular region characterized by an excess of melanocytes. The condition is usually unilateral and classically affects the eyelid, sclera (a white outer layer of the eyeball), uvea (the middle layer of the eye beneath the sclera), and orbit (bony structure of the skull that houses the eyeball), but less commonly, the meninges, palate, and eardrum.
What Are the Causes of Ocular Melanocytosis?
There are currently no known causes of ocular melanosis. Lesions are most commonly present at birth. However, it can also develop during puberty or pregnancy. This may be due to the hormonal changes that occur during these periods. Ocular melanocytosis pigmentation occurs because neural crest cells do not migrate to the basal layer of the epithelium. This condition is associated with black tumors in various parts of the body, including choroidal melanoma.
What Are the Risk Factors for Ocular Melanocytosis?
Ocular melanosis is a rare congenital condition. It is more common in women, especially those of Asian or African descent. It is less common for Caucasians to develop ocular melanosis. However, the risk of later developing cancer is much higher in people with ocular melanocytosis.
What Are the Symptoms of Ocular Melanocytosis?
Hyperpigmented unilateral (appearing on one side of the body) lesions are the main feature of ocular melanocytosis. Excess melanin production causes hyperpigmentation, which causes discoloration. Ocular melanocytosis can appear as partial heterochromia (the presence of multiple colors in the iris of the eye). It can also appear as gray or bluish spots on the sclera (white outer layer of the eyeball). It can also affect the choroid (the inner layer of the eye between the sclera and the retina (the nerve tissue at the back of the eye)), making the retina appear darker.
When to Get Help for Ocular Melanocytosis?
If an individual has discoloration around the eyes, they should get them checked regularly. The eye doctor will monitor the eye pressure for changes that may indicate whether a person has glaucoma. It is also essential to monitor changes in the size and shape of developed lesions. If the lesion grows or changes shape, it may be a sign that the area has become cancerous.
How Is Ocular Melanocytosis Diagnosed?
An eye doctor can perform a few clinical examinations in order to diagnose ocular melanosis. These include:
Slit Lamp Examination - A slit lamp is a bright light microscope. This allows the provider to see the layers above and inside the eye. This allows the doctor to see if the pigmentation is in the sclera (the white of the eye) or the conjunctiva (the outer layer of the eye).
Gonioscopy - People with ocular melanocytosis have an increased risk of developing glaucoma. Because of this high risk, an ophthalmologist may perform a gonioscopy. This examination uses a slit lamp and a prism to allow the provider to see the outflow angle of the eye. The drainage angle ensures proper drainage of fluid in the eyeball. Gonioscopy is particularly useful in identifying a person's type of glaucoma.
Ophthalmic Ultrasound - An ophthalmologist may do an ophthalmic ultrasound to examine the choroid of the eye. This layer contains:
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Iris - The colored part of the eye
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Choroid – A layer of blood vessels
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Ciliary Body - A layer of muscle that helps alter the shape of the lens of the eye. Ophthalmic ultrasound uses sound waves to create images of the internal structures of the eye. This test helps doctors look for signs of choroidal melanoma.
Dermoscopy - If pigmentation also appears on the skin and eyelids, a dermatoscopy can help. Doctors use a dermatoscope, a magnifying glass with very strong light, to examine the texture and color of the skin. This allows the doctor to see the pigmented lesions better.
What Is the Treatment of Ocular Melanocytosis?
Ocular melanocytosis is harmless and does not require treatment. However, regular checks are recommended. People with ocular melanocytosis or nevus of Ota are at increased risk of developing glaucoma or melanoma. It can be treated with radiation or surgery. Treatment depends on the size and location of the lesion and the patient's medical condition.
What Are the Complications of Ocular Melanocytosis?
These patients are at increased risk of developing glaucoma or melanoma in the affected eye. If the nevus affects both the periocular skin and the eye. Glaucoma creates pressure that can damage the optic nerve. When not treated properly, glaucoma can lead to blindness. Treatment options include prescription eye drops and laser surgery.
Conclusion:
A condition characterized by brown, blue, or gray patches, usually on the inside of the eye and on the skin near or around the eye. It can also affect the eyelids and mouth. It is caused by an increased number of cells called melanocytes in the skin and eye tissues. Melanocytes produce a substance called melanin that gives skin and eyes color. Oculocutaneous melanocytosis can increase the risk of glaucoma and a type of eye cancer called intraocular melanoma. It may also be called nevus of Ota. Usually, it is a harmless lesion and requires no medical intervention, but sometimes the lesion can grow excessively, leading to compression of the optic nerve and glaucoma. It is advised that regular checkups should be done in patients with ocular melanocytosis.
