I have been diagnosed with cataracts in one eye. what has caused this.
It's from a combination of things but basically, your age. Some are congenital and others can be related to injury. Even the UV from the sun can contribute.
Many people get them, more than about 1/2 the population by 80. They are common in your 40's or 50's. Basically it is a clouding of the lens. Treatment depends upon how advanced it is. At first, new lenses (glasses) may help. Eventually you'd need to have the lens replaced.
Talk to an opthalmic surgeon, they are your best resource, NOT an optometrist or optician.