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.

Vision health is of the utmost importance to us at Point Grey Eye Care, so we wanted to help you understand the different roles of specialists out there. There are so many different types of vision specialists, we thought it might be helpful to run down all the differences and their educational backgrounds so you understand specifically who you are seeing and what role they can play in your vision health.

Optometrists

Optometry is a specialty of vision that is primarily responsible for the health of your eyes, your “visual system” and the different parts that help you see. An optometrist will examine your eyes to make sure they are working properly, to diagnose any eye diseases or disorders. They are the ones who will test your eyes, prescribe any glasses or contact lenses and treat you if you do have any eye disorders or diseases. Optometrists are highly educated as well; once they finished their four-year undergraduate degree, they go to optometry school for another four years before they receive their O.D. (doctor of optometry degree). And if they want to specialize in pediatrics, contact lenses, neuro-optometry, etc, they must complete a residency program as well which can be another few years depending.

Ophthalmologists

Ophthalmologists are quite simply eye doctors; they are medical doctors who have specialized in the function, diseases and anatomy of the human eyes, as well as perform surgery if required. They are trained to diagnose, prevent and/or treat surgical, medical and refractive problems as they relate to diseases and disorders of the eyes. Ophthalmologists can treat the eyes in a variety of ways including prescribing medicine, glasses or contact lenses and even performing surgery in order to improve or prevent further damage to your vision. Becoming an ophthalmologist is no easy task; after they spend four years in medical school, there are another four years of internships and residencies in hospitals that are further required. This is when decide if they are going to invest more time in a vision specialty like geriatrics or glaucoma, etc.

Low Vision Specialists

As an ophthalmologist or optometrist, you can receive further training to be specialized in low vision issues. This allows testing, diagnosis and treatment in order to treat certain eye problems. Some patients who are progressively losing their vision can see low vision specialists to determine if certain things optical and non-optical devices or a change in lighting and other equipment might assist with their problems.

Opticians

An optician is a healthcare professional who specializes in preparing and dispensing glasses and contact lenses. They are trained to read your vision prescription that tells them exactly what you need for each eye in order to see better. They make sure your glasses and lenses as well as your contact lenses fit properly. They have gone through an accredited post-secondary school program and have learned through on-the-job training as well as there are technical skills required to measuring eyes, understanding prescriptions and adjusting frames and so forth. Some opticians are also able to provide low vision devices and artificial eyes with extra training.

It should come as no surprise to anyone that hormones can completely change everything about a person, from the inside out. And as we’ve discussed over and over, your vision and eye health is no different then any other part of your body. So yes, hormones can and do affect your eyes and vision in more ways then one.

What Are Hormones?

Before we begin talking about how hormones affect us, it’s probably a good idea to start with describing what hormones are exactly and what they do in general. So here we go. Hormones are basically molecules that are produced by glands that make your body do things. They travel through your blood stream and prompt a reaction to start. Hormones are responsible for things likes growth, weight loss and weight gain, puberty, determining your sex, metabolism, sleep, hunger, mood, your immune system, etc. OK so that’s an extremely simplified version but I think you get the point: hormones do everything.

Now that we got that out of the way, let’s think about the ways certain hormones can affect the eyes.

The Colour Of Your Eyes

Inside your throat (so to speak) is a gland called the thyroid gland. And the thyroid gland produces thyroid hormones. These hormones control a lot of things, including the colour of your eyes. The colour of your eyes is actually determined by the wavelength of light the cells in yours eyes are sensitive to. These cells, called cones, function as photoreceptors and are essentially triggered when there is light.

The thyroid hormone will cause a reaction in the cones which will make it start to produce a certain type of pigment (colour). This pigment is what will determine the colours (or wavelength of light) it is most sensitive to, and in turn, dictate the eye’s colour. As a result, the colour of a person’s eyes can change throughout its lifetime depending on the signals sent by the thyroid gland.

Pregnancy and Hormones

Every woman knows that once you get pregnant, your body’s hormones will take you on a roller coaster ride. Sorry for the bad (but accurate) analogy. Not surprisingly, these ups and downs with your hormones can also cause changes in your vision. Most of these changes are temporary and your vision will revert to its normal self once you’ve given birth or have finished breastfeeding. However in some small instances, these changes are cause for concern and you should speak with your eye doctor to ensure they check it out. Most of the common problems are dry eyes and blurry vision. However if you develop high blood pressure you’re at risk of also developing preeclampsia which can be very serious. The signs include seeing strange lights like auras or having temporary vision loss.

Pregnant women are also at risk of developing gestational diabetes which can cause serious harm to the retina’s blood vessels resulting in irreparable damage to the eyes.

Dry Eyes

A very common vision health problem, dry eyes is more prevalent in post-menopausal women. With the decrease of female hormones during this time of life, many side effects occur such as hot flashes, mood swings, and vision problems. Though dry eyes isn’t something to be overly concerned about as it is easily treatable with over-the-counter tear gels and eye drops, in some instances dry eyes can result in infection and impaired vision.