Eye melanoma occurs when the pigment-producing cells in the eyes divide and multiply too rapidly. This produces a lump of tissue known as a tumour.
It's not clear exactly why this occurs, but the following factors may increase the risk of it happening:
lighter eye colour – if you have blue, grey or green eyes, you have a higher risk of developing eye melanoma compared with people who have brown eyes
white or pale skin – eye melanoma mostly affects white people and is more common in those with fair skin
unusual moles – if you have irregularly shaped or unusually coloured moles, you're more at risk of developing skin cancer and eye melanoma
use of sunbeds – there's some evidence to suggest that exposing yourself to ultraviolet (UV) radiation from sunbeds, for example, can increase your risk of eye melanoma
verexposure to sunlight – this increases your risk of skin cancer, and may also be a risk factor for eye melanoma
The risk of developing eye melanoma also increases with age, with most cases being diagnosed in people in their 50s.