Dōjutsu (瞳術, English TV: Visual Jutsu, Literally meaning: Eye Techniques) are genetic ninja abilities that utilise the eyes, granting the wielder ocular abilities. Being a by-product of specific kekkei genkai, dōjutsu are not classified as one of the major jutsu types. They do not require the use of hand seals and in some cases facilitate in the use of or defence against genjutsu, taijutsu and ninjutsu and then defeat their opponent. All known dōjutsu also provide the user with some unique abilities, such as an extended field of vision or predictive capabilities. The use of dōjutsu often-time consumes a great deal of chakra. It should also be noted that along with the eye itself, techniques that stem from the eye's use are also known as dōjutsu. Some of those techniques can be used without an activated dōjutsu and even if the user does not actually possess eyes at all.
By transplanting the eye in question, it is possible for people to possess the dōjutsu, despite not being in the clan that the dōjutsu originates from. Among all known dōjutsu, the Byakugan, Rinnegan, and Sharingan are known collectively as the Three Great Dōjutsu (三大瞳術, San Daidōjutsu, English TV: Three Great Visual Jutsu, Literally meaning: Three Great Eye Techniques).
The concept of dōjutsu may have been inspired by Futaro Yamada's 1959 novel, The Kōga Ninja Scrolls (甲賀忍法帖, Kōga Ninpōchō), which featured two warring clans of ninja that had developed mutations and abilities through selective breeding, with the young heirs to each clan possessing mysterious dōjutsu.
Another possible inspiration for dōjutsu in the series may also be found in the Journey to the West classic's titular character, the Monkey God-King, Sun Wukong: After having eaten all of the 'peaches of immortality', the 'pills of longevity' and drunk all of the 'wine of immortality', and then was captured after a long rebellion against Heaven, the Monkey God-King, Sun Wukong, was then sealed into Lao Tzu's Eight Trigram furnace to be burned to ash in order for Lao Tzu to reclaim his pills of longevity. But after 49 days, Sun Wukong broke out--stronger than ever--his body having been refined by the flames instead of being reduced to ash. His eyes had also become a fiery red and golden colour, becoming known as his "Fiery-eyes golden-gaze" (火眼金睛, Huǒyǎn-Jīnjīng); an eye condition that allowed Sun Wukong to now see what's really there just by looking and the ability to see and recognise the real form of evil despite whatever form that it took on — but, likewise, it also gave him a weakness to smoke, fogging his vision.