Eyes are some of the most complex, intricate and fascinating parts of the body. In fact, there are more than two million parts to the eye, which means after the brain, it’s the most complex and intricate organ in the body. We’ve compiled a list of interesting and strange facts about eyes, that we thought we would share with you.

Size.

Unlike some parts of your body, your eyes don’t grow as you age. This means, your eyes are essentially the same size when you are born, as when you’re a full-grown adult. And it has been proven that a fetus in its mother’s womb will start to develop its eyes only two weeks after conception takes place.

You can only see part of it.

On average, only one-sixth of your eye is actually exposed to the outside, the rest (the five-sixth) of your eye is safely being protected inside your head. Because the eye is such an intricate organ, with highly complex physiology, over time, the body has evolved to protect as much of it as possible. And since most of the functions of your eye happen where you can’t actually “see” it, your skull protects it from being damaged.

Blinking.

How many times do you blink? A lot. They say people blink an average of 17 times per minute; 1,020 times per hour; 24,480 times per day; 171,360 times per week. All the way to 9 million times per year. This also makes the eye the fastest muscle in the whole body, hence the expression, “In the blink of an eye.”

Tears.

Tears are a way for the eyes to defend themselves from foreign bodies such as microscopic items, dust, dirt, debris, bacteria and other such things that could potentially harm your eyes. However, you also produce tears when you’re sad. When you sneeze or have allergies, when you hurt yourself, and so on. Scientists have been able to prove that different tears are chemically different.

What you see.

In order for your eye to process what it sees, it has to translate the information. The way it does this is by turning the image upside down and dividing it in half, similar to cameras. Within a fraction of a second, your eyes, specifically your retinas, will rotate the image and piece it back together in order to send a proper “picture” back to your brain to let you know what you are seeing. This happens so quickly we never even realize it’s happening.

Red.

Although yellow, blue and red are considered primary colours, your eyes, again specifically your retinas, don’t actually see red. With the millions of receptions in your retinas, they are able to process blue-green and yellow-green colour-combinations, which means by process of elimination your brain is able to deduct that any other colour-combination will fall into the “red” category.

Red eyes in photos.

Raise your hand if you’ve ever looked at a photo of yourself and you had red eyes in the pic. We all have. Now with things like PhotoShop we can remove “red eye” but what causes it is actually the light from the flash reflecting the blood vessels at the back of your eye in a layer of tissue called the choroid. The choroid is found behind the retina and contains so many blood vessels (which are red from the blood) and when the flash gets reflected back, that’s what you end up seeing in the photograph.

Unique.

Fingerprints were once thought to be the only unique and distinguishing feature in a human. However the more we learn about eyes, the more we know that in fact the eyes are even more than fingerprints. Fingerprints have 40 unique characteristics while the eye has more than 256 unique characteristics within the iris (the coloured part of the eye). This is also why biometric eye scans are more secure than fingerprint scans.

Processing information.

Because of the rapid rate at which our eyes are processing information, we are constantly taking in and analyzing. Some scientists suggest that your eye can focus on 50 different objects per second. That can be as much as 3,000 objects per minute or 180,000 objects per hour. So just think of what you’ve actually seen (and noticed) that you didn’t even realize!

Most people with prescription eye glasses not only have one pair for indoors, but also require prescription sunglasses, so they can see when they are outside in the heavy sunlight. If you have two pairs of glasses, then you know the strain this puts on you in terms of having to carry around two pairs of glasses, as well as having to pay for two pairs of prescription glasses. And most of the insurance companies won’t cover all those costs, so it falls on you to pay for the difference.

There is a solution. A simple one at that. Getting photochromic lenses.

What are photochromic lenses?

Photochromic lenses are prescription lenses that automatically darken when they are suddenly exposed to sunlight or get back to being clear when you are indoors or when it gets darker.

Originally developed in the 1960s by the Corning company that used to manufacture Pyrex and Corningware, photochromic lenses are now more commonly known as transition lenses after the company (Transition Optical) that is the most well known in the market. But there are many different companies and brands that manufacture such lenses, and your optometrist can advise you on the best choice for the eyewear you select.

From a scientific standpoint, what sets these types of lenses apart is what they have that you actually can’t see. Extremely small molecules are part of the make-up of these lenses and when a large enough amount of UV rays hits the lens, these molecules react to the light. By structurally changing, the molecules are then better able to absorb a large amount of visible light and that is what causes them to darken. Conversely, once the light or UV rays are removed (or you go inside in a darker setting), the process is reversed and the molecules go back to their original shape and the lenses become transparent again.

Who needs photochromic lenses?

Your optician will give you the option of whether or not you would like these types of lenses. The choice is yours. But you should understand what their benefits are so you can make an informed decision as to whether you should get them or not. Here are a few points to consider.

1. Cost: Yes there is an added cost to have a special coating put on your lenses. However consider the cost of having two pairs of prescription eyewear (sunglasses and regular glasses). Your insurance company might not cover the total cost for both pairs, so you might be out of pocket.
2. Protection: Sure you might have a pair of sunglasses in your bag or purse that you can switch over to. But how often do you do that if you’re just going for a short walk to the corner store? The truth is, it takes very little time for UV rays to start affecting your eyes. By having your glasses automatically change to the appropriate level of protection, your eyes are literally always covered. It’s as simple as that.
3. Convenience: Not to mention, if you don’t have to always carry two pairs of glasses with you, that quite literally takes a weight off. Imagine the extra space in your purse or bag. Not having to shuffle through to change from one pair to the other.
4. Adaptability: These lens coatings are available for a variety of lens materials and adapt to work with different types of lenses including bifocal and progressive. So regardless of what you need, your covered.

In the last part of our series in describing the eyes and how they function behind the scenes, we will examine how light is processed and the function of tears. Let’s begin!

Rods and Cones

We’ve already discussed the retina and how it has special cells called rods and cones which work to process light. Each one of your eyes has an astounding 120 million rods and an incredible 7 million cones. This is to help you see in great detail different shades of colour, as well as forms and shapes of items.

Rods detect the form and shape of items and specifically translate black, white and grey colours. Although rods can’t distinguish colour, they are what help you see things even when it’s very dark because they are so sensitive.

Cons, on the other hand, can distinguish colours, but require light for that. And within the cone family, there are three different types of cones. Each type of cone is specifically designed to distinguish a particular family of colours, red, green ad blue (the primary colours). These colours, as we learned early on, are the foundation of all other colours. The combination of these three different types of cones are what allow your eyes to see and detect the millions of different colours in the world.

Tears

Tears are an important part of the eyes and vision process. Tears are made from the lacrimal glands. The same way blinking helps keep dust and other little particles out of your eyes, tears do the same. When you blink, a small amount of tear fluid is secreted which also helps remove these small particles and ensures they don’t go into your eyes.

The other job tears have are to prevent your eyes from drying out. Once your lacrimal gland releases a bit of that fluid, it is then drained into your tear ducts. If you hurt your eye, have something in your eyes, your eyes will produce extra tears to protect the eye itself.

And of course, we all know that when we are sad, or laugh way too hard, we produce tears. Though crying doesn’t protect your eyes, tears are formed as a result of your brain sending a message to your glands.

Take Care Of Your Eyes

In the last few weeks, we’ve examined all the wonderfully complex parts of the eyes that work together, undetected, to allow you to see objects, colours, from a far and from close up. All in the blink of an eye, these things happen. But just as quickly, one can lose their vision. So it’s incredibly important to protect your eyes and treat them as you would any other part of your body. They are, in fact, more sensitive then other parts.

The things you should do to ensure you maintain healthy eyes, include maintaining a healthy lifestyle (including eating right and not smoking), protecting your eyes from UV rays, and wearing protective lenses when necessary, and having regular check ups with your eye care professionals to ensure everything is ok and there are no signs of disease or problems.

Last week, we went through the different parts of the eyes, including the iris, the pupil, the sclera and the cornea. This week, we examine the lens, the retina and how they work together to process light and how your eye muscles and your brain translate this information into vision.

When The Moon (or Light) Hits Your Eye Like A Big Pizza Pie… That’s Vision!

Once light goes into your eye through the pupil, it automatically hits the lens. The lens is located behind the iris and is transparent, so you can’t really see it (unless you have special machines like the doctors). The retina, situated at the very back of the eyeball, receives the light rays that have been received by the lens. The retina has millions of light-sensitive cells (called rods and cones) that convert the light information into nerve signals that are sent to the brain which translate information into vision.

Think of the lens in your eye like a movie project at your local Cineplex Theatre. If you’ve ever looked behind you to the top of the projection booth, you’ll notice light coming from that little window. That light has passed through a powerful lens and focuses the movie’s images onto the big screen in front of you. If you think about this example in terms of your eyes, the movie screen at the front of the theatre is like your retina.

Eye Muscles

The next big factor in vision, involves the muscles of the eyeballs. Lenses are held up in place by a grouping of fibers that are attached to the ciliary muscle. This muscle can actually change the thickness of your lens. For instance, if you are looking at objects that are close, your lens needs to be thicker however when you are looking at objects that are further away, the lens becomes thinner. This helps the lens process the image you are looking at and focus the right image on the retina. Just like how your camera has to refocus depending on whether you are taking a photograph of a flower close up, or mountains in the background.

The Vitreous Body

What you see when you look in the mirror is typically just the eyeball (or there’s the lids too), but what you don’t realize is that your eyes are like icebergs: two thirds of your eyes are found behind the eyeballs. This main part of your eye is called the vitreous body and gives the eyes its round shape. The vitreous body consists of a clear, gelatinous material called the vitreous humor and serves to direct the light that has gone through the lens to the back of the eyes.

The Brain

Now think of the nerve that connects to your eyes from behind (called the optic nerve), as the messenger of sight. The cells inside the retina convert the various objects and shapes and colours you see into messages that the optic nerve can carry to the brain. Think of your optic nerve as your high-speed internet cable that connects your laptop with the web. When you see something, it’s important that the information you are seeing be translated into bits and bytes (or 1s and 0s), so that your brain can understand it.

The eyes are the window to the soul as they say. But they are also a very intricate piece of biological machinery that we use every day without even thinking about it. We’ve broken down the eyes, their many parts and how they function into a three-part blog series so you can have a better understanding of what’s going on inside your eyes and head.

Eyes are constantly taking in information whether you realize it or not. From the colours around you, to the objects in the far distance to when you read and write and beyond. The information collected is then sent to your brain and that is how you know what you are seeing.

The Basics

Your eye balls are nestled inside your eye sockets inside your skull. And from the outside, the eye balls are protected by your eyelids. Whenever you blink (which is several times a minute), you are protecting your eyes by keeping the moisture in. Whether you’ve noticed or not, your eyelids also protect your eyes in other ways. When you encounter bright light (like in the sun for instance), your eyes automatically close in which allows your eye time to adjust to the sudden brightness. Similarly, if something gets too close to your eyes, the lids will blink in order to make sure nothing gets in. Meanwhile your eyelashes have their own job which is to keep dirt and other particles out of your eyes.

What You See

On the outside, you can see the white part of your eye, as well as the coloured (green, blue, brown, grey) and the black parts of the eye. The white part is called the sclera and covers most of the eyeball and keeps everything together, including the tiny blood vessels you see if you look really closely.

What You Don’t See

There is a transparent layer overtop of your eye that is called the cornea, specifically over the coloured part of the eye (the iris). The cornea is what helps your eye focus when light comes into the eyes and is made of a clear tissue. The anterior chamber sits between the cornea and the iris, and is a clear space filled with a transparent fluid that feeds the eye with all the nutrients it needs to stay healthy.

The Iris and the Pupil

The cornea covers the iris, the pupil and the anterior chamber of your eyes. The iris is the colourful part of your eyes. The iris has small muscles that are attached that manage how much light the iris lets in through the pupil, which is the black circle in the centre of the eye. You might have noticed your pupil can get smaller or bigger depending on how bright (or dim) it is; this is how it helps the eye sees under darker conditions. By getting bigger, the pupil lets in more light which makes it a little bit easier to see. And when there is too much light, the pupil gets smaller so as not to overwhelm the eye with the brightness.

Next week we’ll talk about what’s going on behind the scenes. The lens, the retina and how they process the light as well as the eye muscles, the brain and how they translate the information into sight.