The Occulobe, also called the Eye of Vengeance, is the 10th of the 19 genetically-engineered gene-seed organs that are implanted into a Space Marine Neophyte to produce a new Astartes. This implant sits at the base of the brain after being implanted along the optic nerve and connected to the retina, and provides hormonal and genetic stimuli which enable a Space Marine's eyes to respond to the optic-therapy that all Neophytes must undergo in their Chapter's Apothecarium. These procedures, in turn, allow the Chapter's Apothecaries to make adjustments to the growth patterns of the eyes and their light-receptive retinal cells. The result is that Space Marines have visual acuity that is far superior to that of baseline humans and they can see in low-light conditions and near-darkness almost as well as in bright daylight.
- Codex: Space Marines (5th Edition)