Light pollution's effects #2:

Visual Impairment (Glare)

Your nighttime vision and safety are compromised by glare, which results when a light source forces the eye to adapt to a brighter scene than is actually present. Glare diminishes your ability to see well at night, because the pupils of your eyes constrict in response to the glare — even though everything else around you is dark. Overly bright light also casts harsh shadows that could mask the presence of dangerous obstacles or even intruders.

Discomfort glare is merely annoying, whereas disability glare affects your ability to see well in darkness. As one example of the latter, think how hard it is to see a roadway and its surroundings while driving if another car is coming toward you with its high beams on.

In recent years the role of glare on visual performance has taken center stage in lighting research. New studies on glare are taking center stage at the Illuminating Engineering Society of North America, whose standards and recommendations are closely followed by lighting designers and manufacturers.

Older people are especially sensitive to glare sources. As our eyes age, imperfections in the cornea cause more light to scatter, creating visual confusion in a scene.