Quick Answer: Kara's decision to wear glasses on Supergirl may seem like an odd one. Don't Kryptonians have superhuman vision? For Kara, however, the glasses she wears in her civilian guise actually serve a purpose beyond paying homage to Superman’s own disguise. In addition to being a part of her disguise, the glasses act as a kind of emotional crutch; they are a tie to her deceased father who crafted the glasses and her life before becoming Supergirl.
At first glance, Kara's (Melissa Benoist) decision to wear glasses on Supergirl (2015 - ) seems odd. After all, you may be thinking, “don’t Kryptonians have something like 2000/20 vision?” And while that’s probably true, the glasses Kara wears in her civilian guise actually serve a purpose beyond paying homage to Superman’s own disguise.
Melissa Benoist in Supergirl (2015)
The explanation behind Kara’s glasses is revealed in the March 21, 2016 episode, titled “Manhunter.” As a young girl, Kara was overwhelmed by her developing superpowers in a world where she wasn’t exactly blending in. In an effort to keep Kara’s x-ray vision at bay and help her fit in, her father Jeremiah Danvers, played by Lois & Clark’s (1993-1997) Dean Cain, crafted a pair of lead-lined glasses for her (lead is the only substance a Kryptonian can’t see through).
Hellen Slater and Dean Cain in Supergirl (2015)
Now a young adult, Kara has her powers under control but she still opts to wear her glasses. Why? Though they are certainly a part of her civilian disguise, the glasses act as a kind of emotional crutch for her as well; they are a tie to her deceased father and her life before becoming Supergirl. In this way, shedding her glasses becomes a powerful gesture. She isn’t merely changing her appearance; she is letting go of the uncertainties and inhibitions that defined her life before becoming the ultimate woman of action, Supergirl.
Plus who doesn’t love a good glasses flip?