Many moons ago it was thought that chickens incorrectly needed to be outfitted with rose-colored glasses. The reason for this was to prevent chicken cannibalism, as the sight of blood on a chicken caused a violent, aggressive reaction in other chickens who saw that blood. In response to seeing blood, other chickens would peck at the bleeding chicken, often until dead, which caused a large casualty rate amongst flocks. Because of this, farmers sought to prevent chickens from being able to see blood, hence the development of rose-colored chicken glasses, which neutralized the sight of blood.
Chicken glasses had a red lens for each eye that was attached via moveable hinges, allowing it to sway back and forth. When a chicken raised its head and looked forward, the lens would hang over its eyes, washing the world in red and thus making blood indistinguishable. However, when the chicken lowered its head and looked down, the lens would swing forward, allowing the chicken to see the ground in actual color, thus not affecting their ability to find or recognize food.
Originating in the early 1900's, chicken glasses were all the rage for many years, being used frequently up until the 1970's with great success. Use of these glasses then fell to the wayside as it came to be considered cruel to use them, which was due to the method of fitting and applying glasses to the chickens. Some glasses were fitted with straps, but others were hooked into the nasal cavity of the chicken with a cotter pin which in some cases caused mutilation. In fact, use of these glasses is illegal in the UK and has been since 1982 due to penetration of the nasal cavity by that awful and undoubtedly painful cotter pin. Here in the United States, they are no longer used but are highly desired as collectors' items, commanding prices much larger than the few cents for which they originally sold.
While this technique apparently worked, it is a fad that died many years ago. I have to wonder how it made the chickens feel to see the world awash in red. I once had a pair of red sunglasses and all they did was give me a headache, and that was without being attached to my nostrils via a cotter pin. The world did seem extremely unnatural when colored red, not just to me but likely to the chickens as well. Lucky for them, they can again see nature as it is without painful devices doing harm to their beaks and faces.
(Note: even if you have access to chicken glasses, this article is not intended to encourage their use. In no way, shape, or form do we condone animal abuse.)