Introduction
A choroidal naevus is a benign collection of pigmented cells, which are found in approximately 20% of the population over the age of 50 years. The choroid is the vascular layer that sits between the retina and the sclera of the eye.
Choroidal naevi can undergo malignant change, becoming choroidal melanomas, however this very rare. Possibly 1:5000 naevi undergo malignant change whereas most melanomas arise from new.
Choroidal Naevus
Generally there are no symptoms associated with a choroidal naevus. They generally have been identified by an optometrist or an ophthalmologist.
There are some characteristic features that help distinguish naevi from melanomas. An ultrasound of the back of the eye may help in this differentiation as well as photographs being taken to help exclude growth in the future. A fluorescein angiogram may also be requested.
In cases where the clinician is not sure, or feels that there may be some suspicious or relatively high-risk features, you may be called back for regular review. This does NOT mean that you will develop melanoma – in fact the statistical chances of this are very low in most cases.
confirm it’s benign nature.
Choroidal melanoma
Choroidal melanoma describes a malignant collection of cells occurring in the choroid. The lifetime risk varies according to age and race. Over a whole lifetime the risk is about 1:2500 for a Caucasian, whereas it is about 1:14000 in darker skinned individuals. These figures are a little misleading, since many of these will be occurring in elderly individuals; amongst whom the melanoma will not constitute an existential threat. Choroidal melanomas are extremely rare in the thirties and the peak detection occurs in the 5th and 6th decades.
Choroidal melanomas can spread via the bloodstream to other areas of the body and hence need to be taken seriously. As mentioned previously a few melanomas may arise from naevi, but this represents the minority. The only possible predisposing factor appears to be exposure to sunlight, but even this evidence is weak. Choroidal melanomas do not appear to be inherited, although there are some characteristic changes in the chromosomes (genes) of the tumour that may turn out to be of prognostic significance.
Symptoms
Generally there are none, but sometimes there may be an increase in floaters or flashes, some blurring of vision or loss of field.
Characteristic features
The melanoma will start to grow both horizontally and in thickness. There are some characteristic appearances that occur during this growth such as a mushrooming collar-stud lesion. There may be an associated retinal detachment. There may be some dilated blood vessels seen on the surface of the eye when the tumour is growing towards in the front. In advanced cases there may be pain and inflammation as the tumour spreads through the wall of the eye.
The relative location of the tumour in the back of the eye is of prognostic importance as well as the influence that the tumour may have upon vision.
The melanoma has depth or thickness which is confirmed on ultrasound shown on the right.
Management
Investigations will be made to assess location and extent of the tumour. These will include:
- Blood tests
- Ultrasound – liver and eye
- Photography
- Fluorescein angiogram
- CT scan
- Possible MRI scan
- Possible surgical biopsy to assess cell type, which may influence mode of treatment
Once you have been assessed, a treatment plan will be discussed and agreed upon.
Sometimes, particularly if there is no visual prospect for the eye, the eye will be removed and replaced with an implant and cosmetic shell. The results from this are generally excellent with good movement and cosmesis. It does take a fair bit of bravery to undergo such a procedure. You will be able to receive counselling regarding the benefits, and a full description of what is involved.
If there is a good prospect of saving the eye, either with or without vision, and the tumour is relatively contained the following options are available:
- Cryotherapy – freezing treatment
- Photodynamic therapy – a bright light with photosensitizing agent. This is particularly effective in non-pigmented tumours
- Laser
- Radiation plaque therapy where a radiating plaque as attached to the eye for a period and then removed
- Proton Beam Therapy – currently not available in WA
- Surgical resection
- Chemotherapy where there is documented spread throughout the body
Follow-up
There is no doubt that you will require regular follow-up, possibly for the rest of your life. There is no point in hiding the fact that some people do succumb to this disease but this is certainly unusual. It is beyond the scope of full sympathetic and meaningful discussion here and you should seek counseling in this regard. I send all of my melanoma patients (I would only see one every couple of years) to Dr Tim Isaacs at the Lions Eye Institute. He is an expert in the management of these tumours and is conducting academic research in this area.
Here are some useful links:
Eyesmart logo see under Ocular Melanoma
http://www.eyecancer.com see under Choroidal melanoma
Banner image: Shows a fluorescein angiogram of a choroidal melanoma.
