Irregular astigmatism is commonly caused by which of the following?

Irregular astigmatism is primarily associated with conditions that disturb the normal shape and curvature of the cornea. Trauma or corneal dystrophies can lead to an uneven shape of the cornea, resulting in irregular astigmatism. When the corneal surface is altered due to injury or degenerative diseases, the light rays entering the eye do not focus evenly on the retina, leading to distorted vision.

In contrast, cataracts primarily affect the lens of the eye rather than the cornea, age-related changes might contribute to other visual impairments but don’t specifically cause irregular astigmatism, and diabetic retinopathy affects the retina itself rather than the cornea's shape. Therefore, trauma or corneal dystrophy is the main factor leading to the development of irregular astigmatism.