Learn about different parts of the eye and how they each can be affected by cancer.
The globe of the eye
There are two main areas to the eye – the front of the eye and the back, the eyeball.
The eyeball has three layers sandwiched together:
- the outer white fibrous layer, the sclera
- the middle blood rich layer, the choroid
- the inner coloured (pigmented) layer, the retina
The inside of the eyeball is filled with a clear jelly like substance called vitreous humour. This, and the fibrous white sclera help to keep the shape of your eyeball.
The blood vessels that run through the choroid carry food and oxygen to the cells of the eye.
The retina lines the inside of the eyeball. This is the nerve layer of the eye. The cells of the retina react to light and send messages to the brain through the optic nerve. This makes it possible for you to see.
The front of the eye
The front of the eye is the bit you can see. A thin, clear, moist membrane called the conjunctiva coats the inner surfaces of the eyelids and the outer surface of the eye.
The three layers of the eyeball continue round but they make up different structures in the front of the eye.
The fibrous sclera becomes clear, instead of white. This part of it is called the cornea and covers your pupil and iris.
The middle choroid layer becomes the iris and the ciliary body. The iris is the coloured part around your pupil that covers the lens of the eye. It controls how much light enters your eye.
The ciliary body lies just behind the iris. It has two functions. It is the muscle that controls the focusing of the eye. And it makes the clear fluid (aqueous humour) that fills and shapes the front of your eye.
The middle layer of the eye is called the uvea. The front (anterior) uvea includes the iris and ciliary body. The back (posterior) uvea is the choroid.
The tissues surrounding the eyeball (orbit)
The orbit is the tissue surrounding the eyeball. It includes:
- muscles that allow the eyeball to move in different directions
- nerves attached to the eye
Structures around the eye
Structures around the eye include the eyelids and tear glands. They are called accessory or adnexal structures.
Where it starts
The uveal layer is the most common place for eye cancers to start. You may hear your doctor talk about uveal, iris, ciliary body or choroidal melanomas.
Cancers in tissue surrounding the eyeball (orbit) are called orbital cancers. They are very rare.
Eye cancers can develop in the tissue around the eye, such as the eyelid and tear glands. Doctors call these adnexal cancers.
How common is it
Eye cancer is very rare. Around 750 cases are diagnosed in the UK each year. Almost half of eye cancer cases in the UK each year are diagnosed in people aged 65 and over.