The intensity of light coming out from a TV screen is very high. If this bright light with varying intensity is the only source of light in a darkened room, the eye has to constantly adjust for vision by opening wide or narrowing the iris when a person focuses on the bright screen or looks away from it. The constant adjustments that the eye has to make causes eye strain. Whereas in a lighted room, intensity of the T.V. image is only a little brighter than the surroundings, which makes the viewing easier for the eyes. It is, therefore, advised to have some light in the room while watching the television.
