An ocular implant was an artificial medical device which was used to replace or augment a damaged or missing eye.
By the 2360s, ocular implants were a common medical prosthesis in the United Federation of Planets. In 2365, Doctor Katherine Pulaski offered the procedure to Geordi La Forge, but he refused on the grounds that the technology was not yet advanced enough to afford the same visual range as his VISOR. (TNG episode: "Loud as a Whisper")
By the early 2370s, implant technology had advanced markedly, with bio-neural circuitry replacing the Aroeste interface. In 2372, Admiral Jeremiah Hayes determined that the VISOR posed an unacceptable security risk, and ordered La Forge to undergo ocular implant surgery, or else give up his post aboard the USS Enterprise-E. Though initially resistant, La Forge eventually consented. The implants had mechanized detailing on the irises and pupils of the eyes of individuals wearing them. The implants could be made so that they would resemble normal eyes; however, La Forge decided not to have the implants disguised, leaving the mechanized detailing visible. (TNG eBook: Slings and Arrows: The Insolence of Office and TNG movie: Star Trek: First Contact)
Seven of Nine's left eye was removed and replaced with Borg implants. Upon her rescue by Voyager, the Doctor replaced those implants with an ocular implant designed to resemble her other natural eye. (VOY episode: "The Gift")