Quiz: Do You know Facts About Eyes?

The human eye can see millions of colors. The retina, in the back of the eye, has millions of cones which are responsible for color vision and that respond differently to light of different wavelengths. The three kinds of cones in the human eye are red, blue, and green. All the colors we see are combinations of these colors.

People blink on average about 15 to 20 times per minute. This is so frequent; it means our eyes are closed for approximately 10% of our total waking hour!

We blink to lubricate the eyeballs and to protect them from dust and debris, but that doesn't totally explain why we blink so much. Some research has suggested we also subconsciously blink as a mental resting point in which we briefly shut off visual stimuli, which may serve as a mental break.

The iris – the colored part of the eye that helps regulate the amount of light that enters the eye – has 256 unique characteristics, while a fingerprint has just 40.

Like fingerprints, iris patterns are unique, which is why iris recognition or iris scanning, a form of biometric technology, is becoming more widely used for identification.

Brown is the most common eye color in the world. About half of all people in the U.S. have brown eyes, but worldwide, up to 79% have brown eyes. About eight to 10 percent have blue eyes, followed by 5% hazel, 5% amber, 3% gray, and 2% green. Fewer than 1% of the population has heterochromia, which is two different eye colors.

The fastest-moving muscle in the human body is the orbicularis oculi in the eye that controls blinking. A blink lasts a quick 100 to 150 milliseconds (0.1 to 0.15 seconds).

We blink more often when we talk, and less when we read, which is why our eyes get more tired when reading.

Most babies start producing more tears around two to three weeks of age, but it's also normal for it to take two to three months before you see visible tears streaming down their face when they cry.

Lacrimal glands – the glands responsible for tear production – are not sufficiently developed in newborns to produce enough tears while crying. They may produce just enough to keep the eyes moisturized, but not enough to cry tears.

People usually automatically close their eyes when sneezing as part of an autonomic reflex, which is an unconscious reaction to a stimulus. It is thought that sneezing causes the blinking response as part of a protective mechanism to keep irritants out of the eyes.

However, it is possible to sneeze with the eyes open. And no, your eyeballs will not pop out of your head if you do. But since it is believed that closing the eyes keeps irritants out, it is probably best to keep them shut when sneezing.

If the human eye was a camera, it would have 576 megapixels. Compare that to the Samsung Galaxy S20 Ultra, which has a 108-megapixel camera.

Females can perceive colors better than males. Males might see might see the color blue, but females can better perceive different shades such as baby blue, turquoise, cornflower, or navy.

While males aren't as adept at discerning colors, they are better than females at detecting details and movement at distance.

Some believe that different hormones and hormone levels are responsible for these sight differences, while other research thinks these differences in how the sexes see is rooted in historical roles where females were gatherers that required close-range color differentiation, while males were hunters who had to be aware of predators and prey for hunting.

Diabetic retinopathy, a common complication of diabetes, is the leading cause of blindness among adults aged 20 to 74 years in the U.S. Diabetic retinopathy affects an estimated 4.1 million people in the U.S. and vision-threatening retinopathy affects about 899,000