(I) The eye must have adequate light to perform visual tasks without fatigue. (II) thus, precise mathematical relationships exist between' visual function and the amount of light. (III)Similarly, a shade or globe should be used to diffuse the light, so that the light source is not visible. (IV)Poor lighting causes eyestrain, which is really fatigue of the voluntary muscles concerned with vision. (V)Lighting, on the other hand, that is too bright causes glare owing to the intensity of the light source being much greater than the surroundings.