An ocular implant designed by the EMH of the USS Voyager
Close-up of Geordi La Forge's ocular implants
An ocular implant was a medical device designed to replace or augment a damaged or missing visual organ.
A common medical prosthesis in the United Federation of Planets as early as the 2360s, Starfleet doctor Katherine Pulaski had performed several surgeries involving implants during her career. In 2365, the doctor offered the procedure to USS Enterprise-D chief engineer Geordi La Forge, who declined based on his belief that the technology was not yet advanced enough to afford the same visual range as a VISOR. (TNG: "Loud As A Whisper")
By 2373, however, La Forge had undergone the procedure and received a pair of ocular implants. Similar in appearance to the normal humanoid eye, these implants were distinguished by a vibrant blue color with mechanized detail on the irises and pupils. Offering similar advantages (and disadvantages) as the VISOR, the implants allowed La Forge telescopic vision that included heat-detecting infrared capabilities. Side effects included the occasional headache. (Star Trek: First Contact; Star Trek: Insurrection)
In 2375, severe headaches ultimately lead to the discovery that La Forge's optic nerve had regenerated due to exposure to metaphasic radiation at the Ba'ku homeworld. USS Enterprise-E CMO Beverly Crusher temporarily removed the ocular implants, during which time La Forge was capable of vision using his natural organs, although this effect wore off after he left the Ba'ku homeworld and was no longer regularly exposed to the radiation. (Star Trek: Insurrection)
Geordi La Forge had also received ocular implants in an unknown, alternate future timeframe. (TNG: "All Good Things...")
In 2373, Doctor Julian Bashir of starbase Deep Space 9 suggested that General Martok undergo the procedure to receive an ocular implant after the Klingon lost his eye in combat with the Jem'Hadar Ikat'ika on Internment Camp 371. Martok was adamant that he did "not want an artificial eye". (DS9: "Soldiers of the Empire")
In 2374, the EMH program operating aboard the USS Voyager, lost in the Delta Quadrant, fashioned a custom ocular implant to replace former Borg drone Seven of Nine's cybernetic eyepiece. The Doctor prided himself in matching the color of the implant perfectly to Seven's intact eye. While the implant was indistinguishable from a normal Human eye, the new prosthetic retained Borg components granting Seven enhanced vision. Seven's implant was even better equipped to see irregularities in space-time than a 29th century Federation sensor. (VOY: "The Gift", "Scientific Method", "Relativity", "Imperfection")