Therefore, your eye doctor has told you that you have a freckle on your eye. Should you be worried? It can be several things, but the most likely are choroidal nevus or congenital hypertrophy of benign choroidal melanoma of the retinal pigmented epithelium. Both conditions are usually benign and are not a serious problem. Both should be monitored to make sure they are not malignant melanomas.
Congenital hypertrophy of the retinal pigmented epithelium (also known as halo nevus) is a well-defined, pigmented dark spot within the back of the eye on the retina. Although the size varies, it is convenient to think of it as equivalent to the top of an eraser on a pencil. It is an accumulation of pigment increases in the cells of the retinal pigment epithelium cell layer. This is hypertrophy or an increase in the size but not the number of cells. The blood vessels below him also atrophy, resulting in a small blind spot that he is unable to perceive. While there are often changes over time; it is mainly a stable and inconsequential change and congenital hypertrophy of the retinal pigmented epithelium can be considered as a freckle on the skin. The difference is that you cannot see any changes as if it were a spot on your hand, so serious conditions can progress beyond the treatable stages. In rare cases, a halo nevus can change from a normally flat surface and develop raised nodules. The formation of these tumors is very rare, but ophthalmologists check annually. Usually no more tests other than dilated eye exams are required for 3-6 months after the first observation, and then annually thereafter.
Congenital hypertrophy of the retinal pigment epithelium also occurs in a form called “bear tracks.” Bear tracks are multiple dark spots on the back of the eye that look like bear tracks. They often occur in conjunction with a condition called familial polyps and require more tests to detect colon and rectal cancer. This may be due to a dominant gene that is often considered inherited as a predisposition to colon cancer. Bear Tracks can be seen years before cancer occurs, so they can be a valuable warning sign for your optometrist. Bear tracks may require a referral to another specialist for further evaluation. Not all Bear Tracks patients will develop colon cancer, but it is more likely if they are large, present in both eyes, and there are more than 3 or 4 spots in each eye. Isolated single congenital hypertrophy of retinal pigment epithelial spots is not associated with familial polyps or an increased risk of colon cancer.
Trauma to the retina, either from injury or infection to the eye, can cause dark spots similar to congenital hypertrophy of the retinal pigmented epithelium, but they are irregular in shape. They are due to a real increase in the number of retinal pigment epithelial cells. The main concern in this case is monitoring the condition that caused it. If it is an infection in one of the layers of the eye, it could come back at a later date.
A choroidal nevus is actually like a nevus (freckle) but occurs in the choroid, the level below the retina that supplies circulation to the retinal tissue. These appear as round, gray, generally flat spots and are very common in up to 30% of the population. They are also known as benign choroidal melanomas, although they are not true melanomas. They are due to an increase in pigment cells in the choroid. These types of cells are found in our skin and in parts of the eye. The retina does not have the same type of pigment cells, but instead has pigmented epithelial cells. A choroidal nevus is usually flat, but appears more similar to melanomas in the choroid because it is at the same level below the retina. They require closer observation and sometimes more testing to make sure they are benign spots. Any nevus can transform into melanoma, but it is very rare.
Tests to diagnose any new spots observed may include continuous observation, optical coherence tomography techniques to image the layers of the retina, digital imaging and dye imaging of the retina. A dilated examination of the inside of the eye annually is the only technique that allows ophthalmologists to adequately detect most of these points. Although this can be slightly uncomfortable and cause light sensitivity and mild dry eyes, it should be done by your optometrist. Often times, patients have not had their eyes routinely dilated in the past, so when your optometrist finds a new spot or freckle on your eye, it may not have changed for years. You can rest easy knowing that the vast majority of the time it is completely harmless and only needs to be checked once a year for changes. In areas with high amounts of UV exposure, such as northern Colorado, UV protective sun clothing can help reduce the risk of melanomas. There is some controversy about UV exposure and cancer, and some suggestions that vitamin D may reduce certain types of tumors and colon cancer associated with bear tracks. In the future, use of the sun and moderate UV exposure could become the recommendation.