Young mice are born blind, but they begin to open their eyes after 10 to 14 days. If their mother was exposed to insufficient lighting during pregnancy, they may remain blind even after they open their eyes.
Mice are born hairless, deaf and blind. Their blindness is due to their eyelids and eyes continuing to develop after birth. Initially, their eyelids form a single sheet of skin covering their eyes. While young mice grow hair only a few days after being born and their ears open after about a week, their eyelids do not separate until almost two weeks after being born. Blood vessels in the retina grow rapidly then regress 10 days before birth; mice whose blood vessels do not regress, due to being born premature or their mothers receiving inadequate light during pregnancy, may develop permanent eye damage or even blindness.