Ocular melanomaa type of cancer that develops from melanocytes, which are the cells that produce pigment generally in the skin (but can develop in other areas of the body), or eye melanoma, is a type of melanoma that occurs in the eye. Melanomas develop from melanocytes, which are the cellsthe basic structural and functional unit of all living things 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 tissuea group of cells that work together to perform a function 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 gradea description of how abnormal cancer cells and tissue look under a microscope when compared to healthy cells (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 bloodthe red bodily fluid that transports oxygen and other nutrients around the body 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, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs cells look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumoura tissue mass that forms from groups of unhealthy cells) indicates the size and depth of the tumour.
- N (nodea small lump or mass of tissue in your body) indicates whether the cancer has spread to nearby lymph nodessmall bean-shaped structures that filters harmful substances from lymph fluid.
- 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 localisedaffecting only one area of body 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 advancedat a late stage, far along 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 testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, 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:
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence, potentially including:
- Iridectomypartial removal of the iris.
- Iridocyclectomypartial removal of the iris and the ciliary body.
- Transscleral resectionremoval of an eye tumour (most commonly uveal melanoma) in the ciliary body or choroid through an incision in the sclera.
- Enucleationremoval of the eye and attached optic nerve.
- Orbital exenterationcomplete removal of the eyesocket, including the eyeball and surrounding tissues (muscles, nerves, fatty tissue, and potentially the eyelids).
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Laser therapya procedure that uses an infrared laser to raise the temperature of the tumour to shrink and damage cancer cells.
- Photodynamic therapya procedure that involves inserting a light-sensitive drug (photosensitiser) to shrink and damage cancer cells when exposed to a light source.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
- Complementary therapiesa variety of practices and exercises used alongside conventional treatment methods that may improve wellbeing and sense of control (e.g. meditation, art therapy, yoga etc.).
Risk factors
While the cause of ocular melanoma remains unknown, the following factors could potentially increase the riskthe possibility that something bad will happen 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.
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
If your doctor suspects you have an ocular melanoma, they may order the following tests to confirm the diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Imagingtests that create detailed images of areas inside the body tests, most commonly an ultrasounda type of medical imaging that uses soundwaves to create detailed images of the body .
- Blood teststesting done to measure the levels of certain substances in the blood.
- Eye tests, potentially including:
- Ophthalmoscopyan examination of the back of the eye (fundus) to visualise the retina, optic disc and/or blood vessels; also known as a fundoscopy.
- Fluorescein angiographyan eye test that involves using a special dye and camera to examine blood flow in the retina and choroid.
- Electroretinographyan eye test that measures small electrical signals given off by the eye when exposed to different types of light.
- Biopsyremoval of a section of tissue to analyse for cancer cells.
