Eye freckles, medically known as nevi, are pigmented spots that can appear in or on the eye, much like a mole or freckle on the skin. They are typically common and benign, representing a cluster of pigment-producing cells called melanocytes. These spots are usually found incidentally during a routine eye examination, as they often cause no symptoms or vision changes. While the vast majority of eye freckles remain harmless, a small percentage may change over time, requiring professional monitoring.
The Anatomy and Types of Eye Freckles
Eye freckles are categorized based on their specific location within the anatomy of the eye. The three primary types are the iris nevus, the conjunctival nevus, and the choroidal nevus.
The Iris Nevus is a spot found on the iris, the colored part of the eye surrounding the pupil. These appear as tiny, flat, dark brown flecks on the surface of the iris. Iris nevi are generally harmless and rarely progress to melanoma.
A Conjunctival Nevus appears on the conjunctiva, the thin, clear membrane that covers the white part of the eyeball and the inner surface of the eyelids. This type of spot is often yellowish to brown and may appear flat or slightly raised on the eye’s surface. Conjunctival nevi are the most similar to skin moles in their appearance and are typically very common.
The Choroidal Nevus is located in the choroid, a layer rich in blood vessels and pigment cells situated between the retina and the outer white layer of the eye. This type of freckle is not visible to the naked eye and can only be seen by a doctor using specialized equipment to look at the back of the eye. Choroidal nevi are typically flat, gray, or brown spots and are the most common type of nevus found inside the eye.
Causes and Risk Factors
The formation of eye freckles begins with the clumping of melanocytes, the cells responsible for producing the pigment melanin. These clusters of pigment-producing cells create the pigmented spot known as a nevus. While the exact trigger for this clumping is not always known, several factors increase the likelihood of their development.
Genetic predisposition is a major factor, as individuals with fair skin, light-colored eyes, and a tendency to freckle or sunburn easily are more likely to develop nevi. A family history of eye melanoma also increases a person’s risk.
Exposure to ultraviolet (UV) radiation is also considered a contributing factor, particularly for nevi located on the more external parts of the eye, such as the conjunctiva. Protecting the eyes from the sun is still a recommended preventative measure. The risk of developing certain types of nevi tends to increase with age.
Monitoring and When to Seek Medical Attention
While most eye freckles are benign, their potential to transform into a malignant tumor, known as ocular melanoma, necessitates regular professional monitoring. Ocular melanoma is a rare but serious cancer that can arise from a nevus, particularly the choroidal type. For this reason, a baseline examination by an eye care specialist is necessary to document the nevus’s size, shape, and characteristics.
Patients with a documented choroidal nevus often require regular, dilated eye exams, sometimes every six to twelve months, to check for any signs of change. The benign nature of a nevus is defined by its stability, meaning it does not grow or change significantly over time. Any growth or change in features is a signal for concern and requires immediate attention.
Ocular oncologists use a set of specific characteristics to determine if a choroidal nevus is suspicious for transformation into a small melanoma. A common mnemonic used by specialists, such as TFSOM-UHHD, helps them track these risk factors. These factors include a nevus with a thickness greater than 2 millimeters or the presence of subretinal fluid, which is a collection of fluid under the retina.
Other warning signs include the appearance of orange pigment on the surface of the nevus, which is caused by the accumulation of a metabolic byproduct called lipofuscin. A nevus that is located close to the optic disc or one that causes symptoms, such as blurred or distorted vision, also raises suspicion. If a nevus is confirmed to be growing or exhibits multiple high-risk features, it is often classified as a small choroidal melanoma.
If a nevus is diagnosed as a melanoma, treatment is often necessary to prevent the cancer from spreading to other parts of the body. Treatment options for small ocular melanomas typically involve localized therapies, such as plaque radiotherapy, which uses a small device containing radioactive seeds placed temporarily on the eye wall. Early detection and treatment significantly improve the prognosis for preserving vision and preventing metastasis.