Eyepiece

From Memory Alpha, the free Star Trek reference.

An eyepiece is a cybernetic device replacing one of the eyes of some Borg drones.

A removable component, the Borg eyepiece was capable of detecting a wide visual spectrum as well as providing advanced spacial and geometric perspectives. Some versions emitted low-intensity lasers. (TNG: "I, Borg", Star Trek: First Contact)

After Seven of Nine was freed from the Borg Collective in 2374, the Doctor designed an artificial eye to replace her eyepiece. (VOY: "The Gift")

During the production of Star Trek: First Contact, Borg eyepieces were rigged with complex lighting systems that spelled out, in Morse code, names of several production members including Michael Westmore and Jonathan Frakes.