While there are several risk factors for cataracts, the most common cause is aging. Proteins in the eye degrade over time, making the eye more susceptible to developing cataracts.
However, you may be more at risk if you have diabetes, have had an eye injury, or your eyes have been exposed to the sun without sunglasses for a long period of time. Environmental factors can also play a part, including exposure to toxins.
Cataracts can also be genetic, so if a parent or grandparent suffers from cataracts, you may be vulnerable to them in later life too.