I have just examined a 50-year-old woman. She has no symptoms or signs and good vision in each eye. In her left eye, I can see a pigmented area about one disc diameter in diameter. I have examined it using indirect ophthalmoscopy and it looks flat. What should I do?

This looks very much like a choroidal naevus. This is a flat, benign pigmented area that appears in the back of the eye and is sometimes described as an eye freckle or an eye mole. Symptoms are not helpful in its diagnosis. Choroidal naevi, are typically found on routine retinal examination and are usually asymptomatic, as in this case.

The pigmented area in this photograph has clearly defined margins and you mention that it looks flat with indirect ophthalmoscopy.

Choroidal melanoma also tends to be asymptomatic, although it is more likely to be symptomatic than a choroidal naevus. Symptoms of choroidal melanoma may include decreased vision, flashes, or floaters.

A choroidal naevus can grow into malignant melanoma. Growth over one to two years is a convincing characteristic of an active melanoma. However, it is ideal to detect choroidal melanoma before the recognition of growth, as documented growth imparts an almost eightfold greater risk for metastasis. On the other hand, slow growth of 0.5 mm over many years or decades may simply reflect the natural progression of a benign choroidal naevus.

I would be confident in monitoring the lesion over time and looking for a change, with a photograph or drawing, and description in the clinical records on a yearly basis. Any change in size or shape or appearance can be detected at the earliest opportunity with referral to an ocular oncologist.

During the first year, the patient should be monitored twice; subsequently, they should be evaluated annually as long as the naevus remains stable.

Although the link between UV light exposure and choroidal melanoma has not been proved, sunglasses could possibly reduce ocular melanoma risk.

This is a condition, which many eye specialists will rarely see in a career, if at all, and it takes skill and experience to make this differential diagnosis. Unfortunately, choroidal naevi can convert to choroidal melanomas over time. If there is any doubt, a misdiagnosis can have catastrophic results, and therefore in cases where the practitioner is not sure, the patient deserves a referral to an ocular oncologist.