Cataracts can be caused by many reasons, with the following common scenarios: First, due to aging factors, as age increases, the proteins in the lens of the eye gradually degenerate, leading to cloudiness and reduced transparency of the lens, ultimately resulting in cataracts. Second, cataracts can be caused by eye trauma, where a significant impact can damage the structure of the lens. Third, they can be caused by chronic inflammation within the eye, such as uveitis or iridocyclitis, where the inflammation leads to the degeneration of lens proteins. Fourth, long-term use of steroid medications can affect the metabolism of lens proteins, thereby leading to the development of cataracts.