Eyes can develop pigmented spots visually similar to skin freckles. These spots, medically termed nevi (singular: nevus), are common biological occurrences where pigment-producing cells, called melanocytes, accumulate in a localized area of the eye structure. Like skin freckles or moles, these ocular markings are typically harmless and are often present from birth or develop during childhood and adolescence.
Ocular Freckles and Their Locations
Nevi are clusters of melanocytes that appear in three distinct regions of the eye. The most visible type is the conjunctival nevus, which forms on the conjunctiva, the clear membrane covering the white part of the eye and inner eyelids. These surface-level nevi range in color from yellow to brown and may occasionally contain tiny cysts. Another common type is the iris nevus, found on the iris, the colored part of the eye. These spots are usually flat, do not affect vision, and appear as dark flecks on the iris surface. The third type, the choroidal nevus, is located inside the eye in the choroid, a layer of tissue beneath the retina. Due to their internal location, these spots are not visible externally and are typically discovered incidentally during a comprehensive, dilated eye examination.
Factors Influencing Pigment Development
Nevi formation is influenced by a combination of genetics and environmental exposure. These spots result from melanocytes clumping together, which can be present at birth or develop over time, often linked to the body’s overall pigmentation profile. Individuals with lighter skin, hair, and eye colors often have a higher genetic predisposition for developing nevi, both on their skin and in their eyes. Specific genetic variants, such as those in the IRF4 and HERC2 genes, are associated with the presence of iris nevi. Environmental factors, particularly ultraviolet (UV) light exposure, also stimulate melanocytes in the eye. Similar to how sun exposure causes skin freckles, cumulative UV radiation can increase the likelihood of developing nevi later in life. This highlights the importance of wearing UV-blocking sunglasses as a protective barrier for ocular structures.
Monitoring Pigmented Spots for Ocular Health
While most ocular nevi remain benign, they carry a small risk of transforming into ocular melanoma, a type of eye cancer. For choroidal nevi, this transformation is estimated to occur in about 1 out of 9,000 cases annually, necessitating regular professional monitoring. Eye doctors use specialized imaging, such as fundus photography, optical coherence tomography (OCT), and ultrasound, to document the nevus’s initial size and features. These images provide a baseline for comparison, allowing the doctor to track subtle changes over time. Any documented growth warrants further investigation.
Risk Factors for Choroidal Nevi
Doctors look for specific risk factors that suggest potential malignancy. Key signs include a thickness greater than two millimeters, the presence of orange pigment on the surface, or fluid accumulation beneath the retina. Changes in the nevus’s size, shape, or color, or the onset of new symptoms like blurred vision or flashes of light, should prompt an immediate eye examination.