Ocular melanoma, or eye melanoma, is a type of melanoma that occurs in the eye. Melanomas develop from melanocytes, which are the cells that produce pigment, generally in the skin. However, they can also develop in the eye and possibly other parts of the body.
The eye is a sensory organ that allows us to see by reacting to light. Light passes through the cornea (the clear, front layer of the eye) and enters the eye through an opening called the pupil (the black centre of the eye). The amount of light received by the pupil is controlled by the iris (the coloured portion of the eye). This light is then passed through the lens (the clear, inner portion of the eye) and works together with the cornea to focus light onto the retina (a layer of tissue at the back of the eye that is sensitive to light). The retina then activates photoreceptors (image forming cells) to convert the light to electrical impulses that travel to the brain via the optic nerve, which is then converted into an image.
Ocular melanomas are more common in males, and are generally diagnosed over the age of 50. However, anyone can develop this disease.
Types of Ocular Melanomas
There are two types of ocular melanoma, which are classified by the portion of the eye they develop in.
Uveal Melanoma
Uveal melanoma, or intraocular melanoma, is the most common form of ocular melanoma. It develops in the uvea, which is a three-layered portion of the eye composed of:
- Iris – the coloured portion of the eye that controls how much light enters the lens. Melanomas that form here are often low grade (slow growing) and usually don’t metastasise (spread to other parts of the body). This is the least common uveal melanoma.
- Ciliary body – the part of the eye that controls the shape of the lens and produces the fluid in the eye, called the aqueous humour, that provides nutrients and regulates pressure in the eye. Melanomas that develop here develop quicker and metastasise to the liver more frequently.
- Choroid (or posterior uvea) – begins in the spongy membranous layer of blood vessels (or choroid) between the retina and the sclera (whites of the eye). This is the most common form of uveal melanoma.
Conjunctival Melanoma
Conjunctival melanoma is a rare form of ocular melanoma. It forms in a portion of the eye called the conjunctiva, which is a clear mucousal layer that covers the sclera and lines the inside of the eyelids. It often appears as a clear or pigmented lump, and metastasises to the lungs.
Treatment
If ocular melanoma is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumour) indicates the size and depth of the tumour.
- N (nodes) indicates whether the cancer has spread to nearby lymph nodes.
- M (metastasis) indicates whether the cancer has spread to other parts of the body.
This system can also be used in combination with a numerical value, from stage 0-IV:
- Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissue.
- Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
- Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localised cancer.
- Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
- Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advanced or metastatic cancer.
Cancers can also be graded based on the rate of growth and how likely they are to spread:
- Grade I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
- Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
- Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.
Once your tumour has been staged and graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, stage of disease and overall health.
Treatment options for ocular melanoma may include:
- Surgery, potentially including:
- Iridectomy (partial removal of the iris).
- Iridocyclectomy (partial removal of the iris and the ciliary body).
- Endoresection/transscleral resection (removal of the tumour only in the ciliary body or the choroid).
- Enucleation (complete removal of the eye).
- Orbital exenteration (complete removal of the eye and some surrounding tissues).
- Radiation therapy.
- Laser treatment/transpupillary thermotherapy (an infrared laser raises the temperature of the tumour to shrink and damage the cancer cells in the eye).
- Photodynamic therapy.
- Clinical trials.
- Palliative care.
- Complementary therapies.
For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.
Risk factors
While the cause of ocular melanoma remains unknown, the following factors could potentially increase the risk of developing this disease
- Gender and age (being male and being over 50).
- Having pale skin.
- Having a light eye colour, such as blue or green.
- A family history of melanoma.
- Having a growth on or in the eye.
- Certain skin conditions, such as dysplastic naevus syndrome.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) or optometrist if you are concerned.
Early symptoms
Ocular melanoma is often detected during an eye exam, and may be asymptomatic in the early stages of the disease. As the tumour progresses, some of the following symptoms may appear:
- Poor and/or blurred vision in one eye.
- Loss or peripheral vision.
- Discoloured patches in the sclera.
- Seeing ‘wavy lines’ in your vision.
- Vision flashes.
- A change in pupil shape.
Not everyone with the symptoms above will have cancer, but see your GP or optometrist if you are concerned.
Diagnosis/diagnosing
If your doctor suspects you have an ocular melanoma, they will order a range of diagnostic tests to confirm the diagnosis, and refer you to a specialist for treatment.
Imaging & blood tests
The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), and/or ultrasound, depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.
Eye tests
Your doctor may request a variety of eye tests to check for abnormalities in your eye. One of these tests is called an ophthalmoscopy (fundoscopy), which involves using eye drops to widen your pupil and then looking into a large microscope. This option is beneficial as you may not require a biopsy after this test. Another test, called colour fundus photography, takes images of the back of your eye (fundus) after taking eye drops to dilate the pupil. A transillumination may also be requested, which is a procedure used if you need surgery to determine where the tumour is located in the eye. This procedure works by diming the lights in the room, followed by your doctor shining a very bright light into your eye.
Biopsy
In few instances, a biopsy may be required if the previous measures have come back inconclusive. In a biopsy, a tissue sample will be removed using a needle, and is then sent to a lab for analysis.
Prognosis (Certain factors affect the prognosis and treatment options)
While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on the rate and depth of tumour growth, susceptibility to treatment, age, overall fitness, and medical history. Generally, early-stage ocular cancers have a better prognosis and survival rates. However, if the cancer is advanced and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence. It is very important to discuss your individual circumstances with your doctor to better understand your prognosis.
References
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.