The visual processor was a component of Seven of Nine's post-Borg experience that worked in conjunction with her cortical implant.

While celebrating the christening of the new quantum slipstream drive aboard USS Voyager in 2375, Seven decided to partake in some champagne in effort to perfect her social skills. Upon drinking a single glass of champagne, she became drunk, and experienced what she described as the "malfunctioning" of her "visual processors and motor cortex." Upon the discovery of Seven having a blood-synthehol level of 0.5, The Doctor escorted her to Sickbay to give her an injection of inaprovaline to counteract the effects. (VOY: "Timeless")

According to the script, Seven originally spoke of her "visual acuity" rather than her "visual processor".