The best that a human eye has been recorded to see is around 20/10. That means that a person can see at 20 feet what the rest of us need to stand at 10 feet to see.
It’s possible for your eyes to get sunburned. That’s why it’s so important to wear sunglasses that protect against UVA and UVB rays. Sunburn to the eye isn’t the same as sunburn to the skin, where the effects are relatively immediate with pain, redness and peeling. When sunburn occurs to the eye, it’s over a long, gradual period of time; the prolonged sun exposure will eventually lead to thickened tissue within the eye, which might necessitate eye surgery.
It’s possible for your eyesight to get “better” with age. But that’s not necessarily a good thing, because it could be a sign that something larger is amiss with regard to your health. For instance, if you started out as having a +3 prescription (where 0 is normal vision, +1, 2, 3, etc. means farsightedness and -1, 2, 3, etc. means nearsightedness), but then were to develop a condition that would affect vision, such as diabetes, and make you more nearsighted, that could end up correcting your vision to the point where you went from being a +3 to a 0.
Having 20/20 vision isn’t the same thing as having “perfect” vision. To have 20/20 vision means to have “average” vision. It means that you can see at 20 feet what an average person can see at 20 feet.
The “visual centers” in your brain are actually located at the lower back part of your head. That’s why if you were to fall very hard on the back of your head, it’s possible to go blind temporarily. The optic nerve begins at the back of the eye and, through a series of connections, relays the visual images to the occipital cortex in the very back of the brain.
The length of your eye helps determine what kind of eyesight you have. In addition to the eyes’ lens and corneal function, the length of your eyeball has a lot to do with whether you’re nearsighted or farsighted. People who are nearsighted have a longer-than-normal eyeball, while people who are farsighted have a shorter-than-normal eyeball. Just a millimeter change in the length of the eye will change the prescription for that eye.
Your eyeballs get bigger as you grow up. When you’re born, your eyeballs are each 16 millimeters wide. But by the time you turn three, they will grow to each be 23 millimeters wide. Your eyeballs will reach their maximum size when you hit puberty — around 24 millimeters wide.
Some people have lighter eyes and other people have darker eyes thanks to cells called melanocytes. Melanocytes, the cells that produce color in our skin, are also responsible for producing coloration of our irises. Some people have more melanocytes, which means their eyes are darker — and the number of melanocytes a person has is coded in his or her genetics.
Everyone is born with eyes that are at least slightly lighter than they are now. We aren’t born with any special pigmentation — like freckles or moles — and that same concept applies to eyes, too. That means pigmentation of our irises isn’t fully developed at birth; pigmentation occurs in the first year of life, which means our eyes are darker now than they were when we were newborns.