Vision

Visual perception, or simply vision, was the capacity for sight. Usually, this meant light was processed through one's eyes, by means of the optic nerve. Both form and colour was seen in this way. When one could not see at all, this was referred to as blindness.

Eidetic memory, or photographic memory, was the ability to recall what one had seen before. (TV: Invasion of the Bane, The Wheel in Space, Terror of the Vervoids, The Eleventh Hour) Some people, with a night vision ability, could see well in the dark. (PROSE: Halflife, Tragedy Day) The Eighth Doctor claimed to have excellent night vision, (PROSE: Legacy of the Daleks) as did the Fifth Doctor. (PROSE: Observation)

Burning one's eyes, for example with taranium, could lead to such a state of blindness, (TV: "Devil's Planet") as could, in the case of Time Lords, prolonged exposure to the vaccum of space. The Twelfth Doctor himself became blind after walking outside in a vacuum without a helmet for too long. The Doctor's attempts at restoring his sight failed, leaving him unable to see at all. (TV: Oxygen)

Some people, like King Henry III, were "practically" blind, in his case due to cataracts, unable to differentiate between light and colour. Even with the rudimentary glasses of the time, the King could only see everything as blurred light. The Third Doctor restored the King's sight with his sonic screwdriver. (PROSE: Hiccup in Time)

Sarah Jane Smith believed that dogs could only see in black and white, and wondered if Time Lords saw things differently, too. (PROSE: Rights)

Some species were naturally blind. The Cimmerian race was totally blind and had no concept of either sight nor eyes. They accidentally blinded Orllensa, Mike Ferras and Haliard, but later healed them. (AUDIO: Embrace the Darkness) Slithergees were also blind. (AUDIO: Flip-Flop) The Masters of Dorada lost the organs for sight and hearing when they became disembodied brains, but could still sense others' thoughts. (PROSE: The Dream Masters)

Vision aids
Often, technological aids would be used to help a person to see better, or to see anything at all. Glasses, or spectacles, could be used to sharpen one's vision, (PROSE: Hiccup in Time) to see greater into the distance, (TV: The Daleks) or to better be able to read, as with reading glasses. (PROSE: The Power of the Daleks, TV: The Angels Take Manhattan)

Some devices had night vision modes, also known as infra-red, allowing users to see in the dark. (PROSE: Decorative Purposes) The Eleventh Doctor had sunglasses which could function as thermal imaging scanners. (TV: The Hungry Earth) Other devices allowed for X-ray vision. Daleks had eyestalks which allowed them to visually perceive the outside world, (TV: The Dalek Invasion of Earth, Destiny of the Daleks, Remembrance of the Daleks, Dalek, Into the Dalek) through the Kaled mutants within did have eyes, as well. (TV: Into the Dalek) Destroying or simply covering this eye piece could blind, and therefore incapacitate, a Dalek, who would then move around uncontrollably and fire its weapons in a blind panic, usually accompanied by the frantic screaming of "My vision is impaired! I cannot see!". (TV: The Daleks, The Daleks' Master Plan, Resurrection of the Daleks, Revelation of the Daleks, Remembrance of the Daleks, The Parting of the Ways) However, post-Time War Daleks overcame this weakness. (TV: The Parting of the Ways, The Stolen Earth)

After Davros lost his vision, he used a blue lens on his forehead to see, similar to a Dalek eyestalk. (TV: Genesis of the Daleks, The Witch's Familiar, et al.) He was also capable of opening his true eyes, at least later in life, though he seldom made use of this ability. (TV: The Witch's Familiar)

Metaphysical vision
to be added