It was the day little Stella opened her eyes for the first time. It was also the day Luna found out her daughter is blind.

—-

This revelation for one of the next gen kids took longer than it should have.

Yeah, Stella born blind.
Tho she's not completely one. Bat ponies are able to use echo location, which she learns as she gets little bit older. However, while she can make out shape somewhat because of it, anything else that doesn't have one (like colors) she can't see.

This going to have an affect on Stella's and Luna's relationship