Sito Jaxa wearing a blindfold
A blindfold was an article of clothing, typically made from cloth, worn over the eyes to block the wearer's vision.
In 2152, Jonathan Archer warned Ambassador Soval that he would be blindfolded as a security precaution. (ENT: "Cease Fire")
In 2258 of the alternate reality, Montgomery Scott described the notion of transwarp beaming as being like "trying to hit a bullet with a smaller bullet, while wearing a blindfold, riding a horse." (Star Trek)
In 2370, Lieutenant Worf blindfolded Ensign Sito Jaxa prior to subjecting to the Gik'tal, supposedly a test to allow her entrance into his advanced mok'bara class. Worf then told her to defend herself while he attacked, but after suffering several attacks, she removed the blindfold and labeled the test unfair. Worf told her that she passed, as the real objective was to bring home to her the lesson that "But perhaps the next time you are judged unfairly, it will not take so many bruises for you protest." (TNG: "Lower Decks")
Harry Kim sleeping with a sleep mask
A special type of blindfold, also known as a sleep mask, might be used to help sleeping. Harry Kim used such a mask. He picked up the habit out of necessity at the Academy as his roommate "never slept", but later continued it just because he had gotten used to it. He said it reminded him of being in the womb. (VOY: "The Cloud")
The call sheet listed the item as "Kim's Eye Mask".
In 2371, Captain Jean-Luc Picard found himself wearing a blindfold upon entering the Nexus. (Star Trek Generations)
When Julian Bashir's genetic enhancements became publicly known in 2373, Miles O'Brien told him he would have to stand further back when they played darts and that he would try a blindfold if that did not work. (DS9: "Doctor Bashir, I Presume")
Also that year, Harry Kim discovered the dead body of Taymon blindfolded on his bed. (VOY: "Favorite Son")
When Brunt commented that Quark's assembled team training to rescue Ishka from the Dominion should ambush a couple of Bolians, Nog told him that he "couldn't ambush a Bolian if he were blindfolded and tied to a tree". (DS9: "The Magnificent Ferengi")