(covers information from several alternate timelines)
Eyewear was a category of devices worn over a person's eyes. They could serve to either protect the eyes from the elements or to aid a person's vision.
Sunglasses were a form of eyewear worn by individuals to protect their eyes from a sun's rays. However, due to the dark lenses they possessed, sunglasses could also be used for purposes of nondetection, as Geordi La Forge wore sunglasses while he was stranded in 2063, to hide his eyes from the local residents. (Star Trek: First Contact)
Captain Jonathan Archer wore sunglasses (as well as a hat, which also served to protect the eyes) during his venture into the Vulcan's Forge with T'Pol. He offered his glasses to T'Pol so she, too, would have some protection from the effects of Vulcan's suns. She refused them, however, stating that her inner eyelid would suit her needs. (ENT: "The Forge")
While meeting up with Deanna Troi on a beach somewhere on Earth in 2377, Reginald Barclay wore a pair of sunglasses with an second pair of protective lenses attached to them, to give his eyes additional protection from the sun. (VOY: "Inside Man")
Although Commodore Oh's Vulcan inner eyelids should have been more than sufficient to protect her eyes under Earth's sun, she still wore sunglasses in 2399 when she met with Doctor Agnes Jurati outside the Daystrom Institute in Okinawa. It is possible that Oh wore the sunglasses to minimize her chances of being detected, particularly since she was relating highly sensitive information to Agnes. (PIC: "The End is the Beginning", "Nepenthe")
The VISOR was a device worn by some blind personnel, such as Geordi La Forge, to enable them to see. It allowed vision over a wider section of the EM spectrum than normal vision, but many found the extra information difficult to interpret. (DIS: "Brother"; Star Trek: The Next Generation; Star Trek Generations; Star Trek: First Contact; Star Trek: Insurrection; Star Trek Nemesis)