Most cataracts are due to age-related protein build up in the natural lens in the eye. This causes decreased light reaching the retina and reduces vision.
Cataracts can also be caused by trauma. With significant damage to the naturally clear lens, it starts to turn cloudy and affects vision.
Long term steroid use can also cause cataracts. This is the “posterior subcapsular” type of cataract with classic symptoms of blurred vision and glare symptoms.
Previous eye surgeries done can also predispose to formation of cataract e.g. after retinal detachment surgery, cataract formation accelerates and many may require cataract surgery within 2 years.