I had an interesting case this morning. The brown lesion you see on the sclera (the white part of the eye) is called Primary Acquired Melanosis of the conjunctiva (PAM). This is a potentially dangerous melanocytic lesion that can lead to melanoma of the eye. Most patients have no symptoms, but may notice the cosmetic changes on the surface of the eye. Some patients may notice it changing size, shape, or color (darkening). A small percentage of patients may notice the area being red.
Smaller lesions are typically observed by the doctor for changes. A changing or larger lesion would need a biopsy.
In recent studies, only 16% became larger, and around 5% progressed to melanoma. If removed, they can recur, therefore close follow up with your eye doctor is needed.
Sometimes I have found these lesions hiding behind the eyelid. These can be easily missed and require careful examination with a biomicroscope.
I do think there is a correlation with the lifetime accumulation of UV or sun damage. Yet, another reason why sunglasses are a must for all patients. Any patients using a tanning bed should wear UV protective goggles.