I recently heard of a condition called microphthalmia which is when a rat is born with one eye smaller than the other. It occurs in the womb during development and won't even out later. Maybe that is what your rat has? Apparently cats and dogs can also have this condition.
Also, your rat is soo cute! I love her markings! 😍
Also, your rat is soo cute! I love her markings! 😍