Iris nevi are common, benign pigmented spots that appear on the iris, the colored part of the eye. These growths are comparable to freckles or moles found on the skin. While most iris nevi are harmless, consistent monitoring through regular eye examinations is recommended to detect any potential changes over time.
Understanding Iris Nevi
Iris nevi are growths composed of melanocytes, the cells responsible for producing pigment in the eye. They typically appear as small, pigmented lesions, ranging from light brown to dark brown or even black. These lesions can be flat or slightly raised, and are generally less than 2 mm in diameter. Over 80% of iris nevi are located in the inferior half of the iris.
Iris nevi differ from iris freckles in their depth and stability. Iris freckles are superficial, tiny, dark brown flecks on the iris surface that can change with sun exposure. In contrast, iris nevi are larger, grow deeper into the iris stroma, and are more stable, though they can slowly increase in size over time. Other types of eye nevi include conjunctival and choroidal nevi. These nevi are common, affecting 4% to 6% of adults, and are more frequently observed in individuals of European ancestry, females, and tend to increase in number with age.
Detecting and Tracking Iris Nevi
Iris nevi are identified during routine comprehensive eye examinations. An eye care professional uses specialized tools, such as a slit lamp, to closely examine the iris for pigmented lesions. This allows detailed visualization of the nevus’s size, shape, pigmentation, and impact on the iris structure.
Following initial detection, regular follow-up examinations, often annually or as recommended by an ophthalmologist, are important. These appointments allow monitoring for changes over time. Ocular photography, taking detailed images at each visit, is a common technique to track subtle changes in size, shape, or color.
The Risk of Melanoma
While most iris nevi are benign, they can transform into malignant melanoma. This transformation is rare, with an estimated 4% of suspicious iris nevi showing signs of malignancy within 10 years, increasing to 11% after 20 years. It is important to be aware of signs indicating such a transformation.
Signs that may indicate transformation include:
- Increase in the nevus’s size
- Alteration in its shape
- Change in its color
- Blurred vision
- Eye pain
- Presence of blood in the anterior chamber (hyphema)
Factors that may increase the risk of malignant transformation include:
- Being under 40 years old
- Nevus located in the inferior half of the iris
- Diffuse growth pattern
- Exhibiting feathery margins
Any of these changes or symptoms warrant immediate medical attention from an eye care professional for further evaluation.
Other Associated Conditions
Beyond the rare risk of malignant transformation, iris nevi can be associated with other ocular complications. Secondary glaucoma is one complication, occurring if the nevus causes pigment dispersion obstructing the eye’s drainage system or directly interferes with fluid outflow. Uveitis, or inflammation within the eye, is another uncommon associated condition.
Iris Nevus Syndrome, also known as Cogan-Reese Syndrome, is a distinct and rarer condition. It is characterized by multiple iris nevi, often with other ocular abnormalities like iris heterochromia (different colored irises) or pupillary distortion. Individuals with this syndrome frequently develop secondary glaucoma, requiring specialized management to control intraocular pressure and prevent vision loss.