Causes of glare:
1. Brightness of source – causes annoyance and blinding effect.
2. Total volume of light – more than desired light in the direction of eyes causes discomfort.
3. Location of the field of view – a source of light located too close to the eye causes glare.
4. Contrast with background – fight source against a dark background of wall is tiring to eyes.
5. Time exposure – Eye fatigue is caused if the light is within the field of view for a longer time