White circle in my rats eye?

Hello! This is one my ratties Mars :) she never had any eye injury but a couple of months ago this white circle showed up in one of her eyes. She's 2y 3m so I think she might have become (half) blind due to age? She doesn't seem clumsier/less agile than she was before but I know rats don't rely that much on eyesight. Has anyone seen anything similar before? Thanks in advance! Bonus pics of her being a cutie <3