Effects of Light on Humans


Each time we are exposed to a brighter light, we automatically squint our eyes until our eyes can adjust to it. This is a common effect of light on us, but aside from eye strain, lighting affects our health in a number of ways.

There is a psychiatric disorder called “SAD” or the Seasonal Affective Disorder. This disorder is triggered by the shortened photo period during winter allowing the melatonin – a hormone responsible for sleep, to build above normal level leading to depressed mood, irritability, pronounced fatigue, increased need for sleep (hypersomnia), and an increased consumption of carbohydrates. The usual treatment involves some form of light therapy, from either light boxes, or dawn simulators.

The 24-hour cycle natural clock called the Circadian Rhythm regulates most of the systems in the human body. The brain’s suprachiasmatic nucleus (SCN) releases hormone as a reaction to light or darkness signaling the body when to be energetic or lethargic.

The presence or absence of visible light affects the mood through Neurophysiology based on our cognitive as well as our unconscious perceptions. This part of the nervous system is primarily connected with neurobiology, psychology, neurology, clinical neurophysiology, electrophysiology, biophysical neurophysiology, ethology, neuroanatomy, cognitive science and other brain sciences.

Fatigue and headaches are incidentally caused by poor lighting or by light flickers. In workplaces, bright light has been recognized to increase and stimulate alertness and improve cognitive function. Low levels of illumination calms the sense. Depression and poor immune system are often triggered by the absence of daylight. While emotional stress and other physical ailments can also be linked to insufficient lighting. While uncovered lamp bulbs may cause irritation as light produces UV and radiation.

When artificial light becomes excessive or obtrusive, it is considered as Light Pollution (photo pollution or luminous pollution). Light Trespass is an incidence where unwanted light enters a neighbor’s property such as outdoor light shining over the fence or through the window. This may cause sleep deprivation or evening view obstruction. The excessive use of light or over-illumination are affected by several factors: void of timers to turn off light when not needed, fixtures or light bulbs incorrectly chosen to direct light in certain areas, unsuitable selection of hardware to utilize more energy than needed to accomplish the lighting task, lack of training or awareness to use lighting efficiently, inadequate lighting maintenance and indirect lighting techniques.

The extreme groupings of light is called Light clutter. This light pollution generates confusion and distraction which may cause car accidents. In aviation, light clutter also present hazard to pilots when the safety lighting is muddled up with irrelevant lighting.

The difficulty in seeing caused by direct or reflected light is known as glare and can be classified according to its effect on a person. A blinding glare is when one stares into the sun that could totally blind and leave temporary or permanent visual deficiency. Disability glare is the blindness caused by oncoming car lights or scattering light in fog or in the eye. While discomfort glare, although not dangerous as the two previous types of glare could cause annoyance or irritation.

Source by W Tsang


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