1. How will Vitamin A deficiency cause corneal ulcers?

Vitamin A deficiency causes corneal swelling and reduced sensitivity leading to unhealthy cornea which results in corneal ulcers.

2. How will corneal ulcer cause cataract?

If a perforation occurs due to a corneal ulcer, opposite to the pupil, the lens remains in contact with the ulcer, this result in loss of transparency of the lens. Over a period of time resulting in cataract.