A choroidal nevus is a common, benign pigmented lesion located within the choroid, the vascular layer of the eye situated between the retina and the sclera. Often likened to a freckle or mole inside the eye, most choroidal nevi are harmless and require only routine monitoring. However, some choroidal nevi can convert to life-threatening ocular melanoma.

What is Choroidal Nevus? 

A choroidal nevus is composed of melanocytes, the same pigment-producing cells found in the skin. These lesions are usually discovered during a comprehensive dilated eye exam, as they typically do not cause symptoms and are not visible externally.

Nevi can vary in size, shape, and coloration but are generally flat or slightly elevated and grayish in appearance. While they are most often benign, there is a small risk that a choroidal nevus can transform into a malignant melanoma, which underscores the importance of regular eye examinations.

What Causes a Choroidal Nevus? 

The exact cause of choroidal nevi remains unclear. However, several risk factors have been associated with their development, including:

• Genetic predisposition: Individuals with a family history of nevi or melanoma may be more likely to develop these lesions.
  

• Sun exposure: Just like skin nevi, cumulative UV exposure may contribute to their formation.
  

• Age and ethnicity: Choroidal nevi are more common in older adults and in individuals of Caucasian descent.

Signs and Symptoms of a Nevus

Most patients with a choroidal nevus are asymptomatic, meaning they experience no noticeable symptoms. However, in rare cases, if the lesion affects the retina or causes fluid leakage, symptoms such as blurred vision, flashes, or floaters may occur.

Signs that may indicate a potentially dangerous lesion include:

• An increase in size
  

• Orange pigmentation (lipofuscin)
  

• Subretinal fluid accumulation
  

• Proximity to the optic nerve

How is a Choroidal Nevus Diagnosed?

A choroidal nevus is typically detected during a dilated eye examination and digital retinal imaging. 

More advance forms of monitoring a nevus includes

• Optical Coherence Tomography (OCT)
  

• Ultrasound imaging (B-scan)
  

• Fluorescein angiography (in certain cases)
  

Eye care professionals monitor changes in the nevus over time to determine if there is any progression toward malignancy.

What is the treatment for a Choroidal Nevus?

Most small choroidal nevi do not require treatment. Instead, optometrists recommend:

• Baseline imaging to document the nevus's size and appearance
  

• Regular follow-up visits (every 6 to 12 months) to monitor for changes
  

• Referral to a retinal specialist if suspicious characteristics are detected
  

In rare instances where the nevus shows signs of transformation into a melanoma, treatment options may include laser therapy, radiation, or surgical removal, depending on the size and location.

Prognosis

The prognosis for patients with a benign choroidal nevus is excellent. Fewer than 1 in 8,000 choroidal nevi transform into melanoma annually. With vigilant monitoring and early intervention when necessary, most patients can maintain good vision and eye health.