So – you put on your sunglasses, and your eyes tell your brain that the sun has disappeared, and darkness has begun. To your brain, darkness means the onset of night. Your irises get larger to let more light in, and your focus intensifies. You become acutely aware of the objects in front of you (so you can avoid them), even if you cannot discern what the objects are (Think of walking towards the bathroom night-lite at 2am). Your focus is narrowed because, in the dark, things to the side of your path have become less important. Those are some physical reactions to darkness.

The darker the glasses, the more the brain is convinced it’s night – wrap-arounds, even more so. You might as well put on blinders, your peripheral vision has been greatly diminished, or disappeared entirely. You actually have to turn your head to see objects approaching from your side. Try it.

Your brain and eyes have evolved an intricate relationship over millions of years to help your ancestors survive the dangers of travel at night – even if it’s only to the bathroom.

But, just as there are physical processes that are triggered by darkness, there are other actions that your brain takes as a result of seeing sunlight.

Sunlight is known to trigger many hormones, and some of them are aids for the assimilation of vitamins (vitamin D in particular), while others, like melatonin are produced to protect the skin. Hormones are also the reason that varying degrees of illumination can made you feel everything from drowsy and sad, all the way to happy and active.

There are other actions the body takes to protect itself from the harmful effects of sunshine as well – sweat, and even increased respiration. Some of these reactions are triggered entirely by visual cues – not from specific images, but from clues the eyes interpret as related to heat. And since there can intense light even when it is freezing, the body is alters its reaction based on numerous factors it senses.

The original intent of sunglasses was to reduce glare. Even thousands of years ago, people had fashioned crude sunglasses out of wood (pinholes, or slits) to deal with travel across the snow or ice. Snow-blindness, and glare are real issues.

But now they are fashion accessories, they are worn indoors, in meetings, and I’ve even seen them at night. Does anybody drive a car without them?

Light skinned people, especially with light colored eyes, sometimes must wear eye protection or they may suffer ocular effects just from the reflection of too much sunlight off of their face. Our world is not the primal world. We have a lot of reflective concrete, glass, metal, big shiny signs – our eyes are bombarded with glare constantly. Wind can also be an issue in many outdoor activities, especially biking, sailing, and skiing, but without clear glasses, there are few alternatives for protection.

My view, from Steppen’s perspective, would be wear them when necessary. But be aware that you might need more sun-tan oil because your body might still think it’s night-time, so why should it produce melatonin? Or, while driving, you may not notice the car in the other lane, or you might not see the deer approaching from the highway shoulder as soon as normally would.

Your body, after millions of years without light at its finger-tips, approaches darkness differently than it deals with daylight. So just be aware that, due to implied darkness, your brain may have turned off some functions, and turned on others.

It is also worth mentioning that – No one can respond to your eyes when they are covered. They cannot empathize with you. The responses you ‘trigger’ in interactions with people, may not be what you expect. The eyes help us conduct more than half of our communications with others. Our eyes help others perceive our intent. Our eyes express grief, joy, sadness…