Aside from what brand of contact solution your eyes prefer, there are probably a slew of things you never knew about your eyes. Yes, you may think you know eyeball facts - like the notion our eyes are the same size from birth through adulthood - but many of these pieces of eye trivia are commonly spread misconceptions.
Our peepers are precious and unique. Some people's eyes are color blind (it's not all black and white) and many people take their vision for granted. Our eyes are quite resilient, but they can succumb to disease if you do not properly care for them. They can also give your brain a break, provide extra security in the future, or pop out if you're not too careful. Don't hold the screen too close to your face (thus straining your eyes) while you read these fascinating facts about the human eye.
If you have blue eyes, they aren't a dreamy hue because of colored pigment - the blue actually comes from the structure of the eye itself.
The iris is the colored part of your eye. The iris has a front (the stroma) and a back (the epithelium). The epithelium contains black and brown pigment. Some people have specks in their eyes, and that's the epithelium you're seeing.
The stroma is composed of colorless collagen fibers. When the stroma has melanin in it, the result is brown eyes, as the melanin absorbs light and makes them darker. Blue eyes have no melanin in the stroma and no collagen deposits. So, without any melanin or extra collagen, how do the eyes look blue?
The answer is something called the Tyndall effect. This means the light completely scatters and none is absorbed. (In green eyes, they have little melanin and no extra collagen, so some light is absorbed and some is scattered.) This means in high light or low light, blue eyes will look different, since they have no actual color - at least not in the way we typically think of color.
There is a common misconception that our eyes are fully-formed and adult-sized when we are born. While eyes change in size less than any of our other body parts, they still do grow. An infant's eye is roughly 66% of the size it will grow into as an adult eye. Our eyes grow the most from infancy up until age two; by the time we reach adolescence, the growth of our eyes typically stops.
People blink a lot, probably around 15 times per minute. Assuming you sleep for eight hours (and aren't blinking during this time), that's 900 times an hour and 14,400 times per day. On a biological level, we blink to keep our eyes lubricated. Men and women blink about the same number of times, but strangely, women who are on birth control blink considerably more than women who aren't. In one study, men blinked 14.5 times per minute, and women who weren't on birth control blinked 14.9 times per minute; women who took the pill blinked 19.6 times per minute.
This is a medical mystery. We have no idea why the pill makes women blink more. In animal studies, blinking is linked to dopamine levels, so it's possible the same sort of thing could be happening here.
Retinal scanning has actually been around since the 1980s, but it hasn't been widely used for a variety of reasons: Actually getting someone into the system, so to speak, is a lengthy process. It's not something that can be done quickly for a large number of people. Likewise, the retinal scanning intake process needs several images of the retina in order to function properly, and these can be hard to acquire (imagine holding your eye very still for a very long time as pictures are taken of it). Lastly, it's difficult to get a good image of the retina.
Although retina scanning will never let in the wrong person, it can easily lock out the right person. The scanner will often have to repeat the process multiple times to let someone in.
That being said, it is an extremely secure technology. Someone can alter their fingerprint (on purpose or not), but you're not going to be altering your retina anytime soon. The retina is comprised of blood vessels in a pattern unique only to you - even identical twins have different retinas.
This is different from iris scanning (which scans the pattern in the iris), though the two are frequently confused. And retina and iris scanning are both different from FaceID. FaceID looks at your entire face, not just your eyes, and compares the photo it takes to the photo it created when you "enrolled" your face.