A nevus is a pigmented growth that occurs on or in the eye. They are often referred to as “eye freckles” and are similar to moles on the skin. Nevi (the plural of nevus) are common and usually remains benign (non-cancerous), although in rare cases they can develop into a type of cancer called melanoma.
There are several types of nevi. This blog will explore conjunctival nevus, how it is diagnosed, and if it requires treatment.
What Is a Conjunctival Nevus?
The conjunctiva is the clear tissue that covers the white part of your eye. In some people, a pigmented lesion called a conjunctival nevus appears in the conjunctiva as a small spot or patch. The coloring can range from yellow to brown and the shading may change over time (lighter or darker). It may also appear as raised or flat.
The conjunctiva contains the epithelium (thin tissue on the outer layer) and stroma (supportive connective tissue underneath). A conjunctival nevus originates at the point where the epithelium and stroma meet and typically grows a little into the stroma over the years.
The lesions occur when melanocytes, special cells in the eye that produce the pigment called melanin, clump together. Typically, melanocytes are evenly spread out, but some people are born with the cells closer together (known as a congenital nevus) or their cells grow closer together due to aging or other factors. For example, exposure to ultraviolet (UV) light can increase your chances of developing a nevus later in life.
Other Types of Nevi
Conjunctival nevus is one type of nevus. A nevus may also appear in the eyelid skin, in the iris, or within the posterior region beneath the retina.
Here are some other examples of nevi:
- Iris freckles: These tiny spots occur when melanocytes build up on the iris (colored part of the eye). Like a conjunctival nevus, iris freckles are typically harmless.
- Iris nevi: This type of nevus is similar to iris freckles, except the spots are larger and grow into the stroma. They can grow over time, although they usually remain harmless.
- Choroidal nevus: This type of nevus occurs on the inside of the eye as opposed to outside the eye. A build up of melanocytes occurs in the eye’s choroid, the area between the sclera (white outer layer of the eye) and the retina (thin layer of light-sensitive tissue at the back of the eye). A choroidal nevus that is raised or turns orange may indicate a type of cancer called small choroidal melanoma.
Diagnosing Conjunctival Nevus
A conjunctival nevus can be diagnosed by an ophthalmologist during a routine comprehensive eye exam. Your doctor may also order ultrasonography or optical coherence tomography (OCT) to assess conjunctival thickness.
Since a nevus can change, you should have your eye doctor monitor it at least yearly. The ophthalmologist will examine and image it to determine if there have been any alterations in its dimensions or morphology.
Do you need treatment?
A nevus usually does not impact vision, so it typically does not require treatment unless there are features suspicious of cancer. Even when removal is performed, the surgery is generally well-tolerated without loss of vision.
Your eye doctor may request follow-up appointments to monitor eye freckles with photos or imaging. Contact an ophthalmologist if you notice changes in size, shape or color or if you have vision changes or pain.
Changes could indicate a type of eye cancer called conjunctival malignant melanoma. The risk of conjunctival nevus turning into melanoma is less than 1%, (1 in 300) according to Ophthalmology Times. While rare, this type of cancer can be fatal.
Diagnosing conjunctival melanoma may require advanced imaging and/or a biopsy. To treat conjunctival melanoma, an ocular oncologist may surgically remove the section of the conjunctiva that contains the cancer cells. Cryotherapy (freezing abnormal tissue) is another method used to remove the melanoma and is often performed along with surgical excision. Additionally, radiation therapy or chemotherapy eye drops may be used to limit the spread of the tumor.
With ocular melanoma, eye removal is rarely required. However, if the tumor grows large enough, the eye will be replaced with a custom prosthetic.