Aren’t eyes supposed to be windows to the soul? Actually, they may be more like windows to our brains according to neuroscientists who say they can determine mental effort by measuring the change in pupil diameter. Whatever you see when you look into someone’s eyes can be disconcerting to you and/or to that person who may wish to keep those thoughts or feelings private.
If someone has been crying or hurt, sunglasses can obviously hide tell-tale red, weepy eyes and bruises, but dark lenses can do more than cover up blotchy skin. When eye contact is made impossible by way of a pair of sunglasses, face-to-face communication is radically altered. Instead of allowing direct eye contact, the dark lenses can become tools of intimidation. If you can’t see how someone is reacting, you automatically go on the defensive. It’s considered rude to keep sunglasses on when talking to someone who isn’t wearing a pair themselves and your insistence of wearing them can be taken as an insult.
There are instances, of course, when continuing to wear sunglasses (while in conversation) is completely acceptable. For instance, if you’ve just been to the eye doctor, and have had drops making your eyes hyper-sensitive to sunlight and glare, then your explanation will go a long way to alleviating the other person’s discomfort. Also, people who are vision impaired will often wear sunglasses.
This practice is in fact mostly for the benefit of others (although in some cases, partially blind people do have light sensitivity) – but usually it’s so people don’t have to see eyes that either wander or seem to be looking in the wrong direction.