This is a scary topic. For some reason the thought of ocular (eye) metastasis horrifies us far beyond reason. I felt some of that when I read that a couple of the people in my metastatic breast cancer support group have eye mets, and that is why I did a little reading about it. The purpose of this post is share the information I found and perhaps relieve a little of the fear and horror for others. Note to my friends: I do not have choroidal metastasis or any other eye mets.
First, some numbers. Although most patients with choroidal metastasis (around 85%)1 have a history of breast cancer, the odds of developing it are very low: about 8-10% of people with metastatic breast cancer are clinically diagnosed with ocular metastasis2. Doing some rough math: if about 30% of people with breast cancer develop metastases and around 9% of this group develop ocular metastasis, then the chance of eye mets for people who are diagnosed with breast cancer is only a little under 3%. This is very, very low.
So what is choroidal metastasis? The choroid is the thin middle layer of the eye between the retina (the tissue that converts light into nerve impulses that the brain can interpret as images) and the sclera (the white of the eye; the outer, protective layer of the eye). It is very thin, between 0.1 and 0.2 mm. It is rich in blood vessels and its most important function is to carry blood to the retina.
Choroidal metastasis is usually asymptomatic, but if there are symptoms the most common one is blurred vision. Other symptoms include seeing “floaters” or flashing lights. Since these symptoms are far from specific (most adults have floaters, those little moving shapes or shadows in our field of vision, for example), it is important not to self-diagnose here. If you go to the ophthalmologist (healthy adults should routinely have a medical eye exam every two years), be sure to tell her that you have a history of breast cancer or are living with metastatic breast cancer.
One of the interesting things about choroidal metastasis is that it can actually be seen by the doctor. This means that in most cases the only examination needed to diagnose it is a dilated eye exam with an instrument called an indirect ophthalmoscope that the doctor wears on her head. It is not an invasive exam because this instrument gives the doctor a good, wide view of the interior of the eye. The instrument does not touch the eye.
If choroidal metastasis is discovered on examination and the patient has no symptoms, no particular treatment is required. Patients are referred to an oncologist if they are not already being followed by one, and they are followed more closely by their ophthalmologist or an oncologic ophthalmologist. For patients who do have troublesome symptoms, a kind of radiation treatment may be prescribed. The focus of any treatment is on maintaining quality of life while the systemic disease is treated.
The upshot of what I discovered from a couple of hours of reading is that choroidal metastasis is not such a big scary thing as it might seem, especially looking at it in terms of the more common sites of breast cancer metastasis (bones, lung, liver, brain). I can live with that.
1 Marianne Doran, “How to Spot Ocular Metasases” in EyeNet Magazine (a publication of the American Academy of Ophthalmogy), July/August 2004.
2 Fenton, Kemp and Harnett, “Screening for ophthalmic involvement in asymptomatic patients with metastatic breast carcinoma”. Eye , official journal of The Royal College of Ophthalmologists, (2004) 18, 38–40. doi:10.1038/sj.eye.6700535).
Image credit: “Blausen 0388 EyeAnatomy 01” by Bruce Blaus. When using this image in external sources it can be cited as: Blausen.com staff. “Blausen gallery 2014”. Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. – Own work. Licensed under CC BY 3.0 via Wikimedia Commons.