Occipital implant

From Memory Alpha, the free Star Trek reference

The occipital implant is a device installed on the eyebrows of Borg drones. It provides an attachment site for the eyepiece and allows systems access to the ocular implant.

In 2376, Seven of Nine reported some minor pain beneath her occipital implant after being forced to fight in Tsunkatse matches. (VOY: "Tsunkatse")

In 2377, the Nygean convict Iko asked Seven of Nine if the installation of her occipital implant hurt. At first she replied that she didn't remember, but later she told him that it was one of the most painful experiences of her life. (VOY: "Repentance")

The term "occipital" actually refers to the back of the skull.