Cancer is indeed a scary disease. Just by listening to the word can send shivers down the spine. Cancer can happen to any part of the body. Health screening plays an important role in identifying possible cancer early on. Although not all cancer is dangerous, early diagnosis and treatment can definitely give good outcomes for the patients. Eye cancer is rare in number but the most common eye cancers in adults. In this article, we will be learning about one of the cancers that affect the eyes known as intraocular melanoma.
What exactly is intraocular melanoma? Since it is quite a mouthful word, let’s break it down based on the term and word by word. Intraocular means inside the eyes whereas melanoma is cancer that originated from melanocytes. Intraocular melanoma is a type of cancer that develops in the eyes caused by the abnormal melanocytes. Just as melanoma on the skin, melanoma can occur in the eyes. Intraocular melanoma begins in the middle of three layers of the wall of the eyes. The outer layer is known as the white of the eyes or sclera and the clear part in front of the eyes is known as cornea. The inner layer has a lining of nerve tissue known as the retina. The middle layer where intraocular melanoma forms is known as the uvea or uveal tract. The uveal tract itself has 3 main parts. It is important to understand these 3 parts as it plays a significant role in the progression of the disease.
1) Iris- the coloured area changes the size of the pupil which changes the amount of light entering the eyes. Intraocular melanoma if the iris is usually a small tumour and grows slowly. This kind of melanoma rarely spreads to other parts of the body.
2) Ciliary body- can be found behind the iris and functions to enable the eye to focus by changing the shape of the lens. Intraocular melanoma of the ciliary body is usually larger and likely to spread to other parts of the body.
3) Choroid- layer of blood vessels that supply nutrients to the eyes. Most intraocular melanoma begins in the choroid. It is usually larger and likely to spread to other parts of the body.
It is not clear how eye intraocular melanomas occur but there is a risk factor that has been identified. It is stipulated that intraocular melanoma occurs when the DNA of the pigment cells of the eyes develop errors which then leads to the mutated cells of the eyes and ultimately, melanoma. A person with a risk factor of intraocular melanoma has a high chance of developing one. However, this does not mean not having a risk factor means a person is not going to get cancer. By understanding the risk factor, you can talk to a doctor if you feel you are at risk. Risk factors include a person with fair skin that freckles and burns easily, a person with blue or green or other light-coloured eyes, old people and a White person. Smoking increases risk for this disease. People born with certain growths in or on the eye such as moles or nevi also have risk for developing this cancer. Certain inherited skin conditions such as dysplastic nevus syndrome is considered a risk factor.
The reason why it is important to identify risk factors is because intraocular melanoma does not exhibit symptoms during its early stage since most melanomas develop within the part of the eyes you cannot see. It is usually found during regular eye exams when doctors dilate the pupil to get a closer look of inside the eyes. Plus, when symptoms are present, they are usually non-specific and can be confused with other eye problems. Common symptoms in patient with intraocular melanoma are blurred or distorted vision, dark spot on the iris or the white of the eyes (conjunctiva), blind spot in the side vision, sensation of flashing light, spots that can be seen within the field of vision (floaters) and change in the shape of the pupil. It is rare that this cancer causes pain or red eyes.
Diagnosing eye melanoma usually begins with a dilated eye exam by an ophthalmologist. A melanoma is different with the nevus or mole in or on the eyes. Melanomas inside the eyes may have colours of dark to light brown, orange or sometimes no colour at all. This melanoma is thicker than usual and fluid leaking can be found. If they suspect an intraocular melanoma, a person is likely to be referred to a retina specialist or ocular oncologist. From here, further tests such as ultrasound are used to determine the mass and the thickness. Optical coherence tomography (OCT) may be used to get detailed pictures of the inside of the eyes. In some cases, doctors may even perform a fine needle biopsy of taking a small sample of the tumour cells to be investigated further.
Just like with any other cancer, patients will wonder if intraocular melanoma is curable. This is quite a difficult question as this depends on the size of the tumour and how extensive the spread is. For example, brachytherapy, a common radiation treatment, helps to control 95% of small and medium ones. One thing for sure, intraocular melanoma may not be cured since even up till now, current treatments for advanced eye melanomas are limited and clinical trials of newer treatments are still ongoing.