A pigmented spot in or on the eye, often called a mole or eye freckle, is medically known as a nevus. These growths are common, similar to moles on the skin, and represent a localized collection of pigment-producing cells. Most eye nevi are harmless and present no risk to vision or health. Determining the spot’s location is the first step in understanding its significance and required monitoring.
Where Is the Spot Located?
A mole in the eye is typically categorized by its exact location, which dictates whether it is visible to the naked eye or requires specialized equipment for detection. Spots found on the surface of the eye are generally easy to observe in a mirror. A conjunctival nevus is located on the conjunctiva, the clear membrane covering the white part of the eyeball and the inner surface of the eyelids. An iris nevus, or iris freckle, is a pigmented spot appearing directly on the colored part of the eye, which is the iris.
These surface nevi can range in color from yellow to brown and are often discovered by the individual or during a routine eye check-up. Pigmented spots located internally, however, are not visible without a comprehensive examination. The most common internal spot is a choroidal nevus, which is situated deep in the back of the eye, within the choroid layer beneath the retina.
A choroidal nevus is typically flat and slate-gray. Because it is hidden in the posterior segment of the eye, its presence is usually an incidental finding during a dilated eye exam. These fixed, pigmented spots are distinct from non-pigmented, moving specks sometimes noticed in one’s vision, called floaters. Floaters are small opacities within the vitreous gel and are not nevi, though they should still be monitored if they appear suddenly or increase in number.
Understanding Benign Pigmented Spots (Nevi)
The formation of a nevus is rooted in the clustering of specialized cells called melanocytes. Melanocytes produce melanin, the pigment that determines the color of our skin, hair, and eyes. When these cells aggregate instead of distributing evenly, they form a nevus, which is essentially a benign tumor of pigment cells.
Genetic predisposition plays a role in the likelihood of developing nevi, but environmental factors also contribute. For nevi on the front of the eye, such as those on the conjunctiva, UV light exposure is thought to be a contributing factor, similar to how sun exposure causes skin freckles. This association underscores the value of wearing UV-protective sunglasses for eye health.
Most nevi are stable, meaning they do not change in size or appearance over many years. Choroidal nevi are present in approximately 5% of the population and are frequently discovered in adulthood. Nevi can sometimes be associated with small, yellowish deposits known as drusen, which are signs of a long-standing, benign lesion.
Because nevi are benign, they typically do not require treatment. The standard approach is regular monitoring, where an ophthalmologist takes baseline photographs and measurements to compare against future examinations. This routine surveillance ensures the spot remains stable and benign.
When to Seek Urgent Medical Attention
While the vast majority of eye nevi are stable and harmless, there is a very small risk that one could transform into a form of eye cancer called ocular melanoma. This transformation is rare, occurring in approximately 1 in 9,000 choroidal nevi per year, but it is the reason for consistent monitoring. Certain features indicate that a nevus may be transforming and require immediate evaluation by an eye specialist.
The warning signs often mirror the “ABCDE” features used for skin moles, adapted for the ocular environment. Asymmetry, irregular borders, and multiple colors are concerning, but the most specific indicators for internal nevi relate to dimension and change. Any nevus that shows significant growth or an increase in thickness, especially an elevation greater than 2 millimeters, raises suspicion.
Other high-risk features include the presence of orange pigment on the surface of the nevus or any evidence of subretinal fluid accumulation, which is a sign of cellular activity. These characteristics suggest the lesion is active and potentially malignant, necessitating prompt diagnostic testing and intervention.
Any sudden changes in vision should be reported to an ophthalmologist without delay, including new or significant increases in floaters, flashes of light, or a noticeable loss of sight. For a stable nevus, monitoring typically involves a dilated eye exam every six to twelve months, utilizing imaging techniques like fundus photography and ultrasound to track its size and shape. If a nevus is found to have high-risk characteristics, the ophthalmologist may recommend a referral to an ocular oncologist for specialized management.