Elementary Anatomy of the Human Eye

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Most people have heard the cliche "Eyes are the windows to your soul." Little do people know that when you're looking into somebody's eyes, whether it be that cute boy/girl in school you catch glances from across the room or that menacing boss of yours that you're trying to hide your fear from, you are actually looking through a window. Just.... not exactly into the soul.

Below I am going to outline, from front to back, the very very basic anatomy of the eye so that even the lay-est of layman can have a working understanding of what is going on. Keep in mind, however, the reality is that it is much more complicated than I can present to you.

The lids: This isn't actually part of the "globe" as we call it, but, they play a large function that I believe most people aren't aware of. All along the border of the lids lie little pockets called "meibomian glands" which secrete oil. This oil makes up, in my opinion, the most crucial aspect of your tear film. Oil keeps the rest of your tears from evaporating and therefore keeps your eyes nice and moist.

The Cornea: This is the glass pane of your window. This layer of tissue lies at the front-most part of your eye and consists of a thin transparent boundary. There are nerves in the most superficial layers which is why when you get something stuck in your eye, be it a hair or a fly, it hurts like an absolute bitch. The outer-most layers heal very quickly while inner layers take some time and leave scarring.

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The Anterior Chamber: This is a pocket (seen above as Anterior Cavity) that lies between the cornea and the crystalline lens, which I'll get into in a moment. The anterior chamber largely consists of aqueous fluid and houses the iris. This fluid is transparent to allow for light to enter the eye with absolute minimal scattering. A major cost of keeping this fluid transparent is that the immune system has to be suppressed here. A fully functional immune system includes large gatherings of white blood cells which can cause inflammation where you don't want it.

The Iris: This is the colored part of the eye. Whether you have blue, hazel, or brown eyes depends on the amount of melanin in your iris, just like in your skin. The iris is actually two muscles arranged so that when one contracts the pupil gets larger and when the other contracts it gets smaller. By controlling the size of the pupil the iris controls how much light enters the eye and what your depth of focus is for vision.

The pupil: While the cornea is like a glass window pane, the pupil is like the hole in the wall we typically refer to as a window (however, here the glass pane sits in front of the window opening). The pupil isn't actually a physical object, much like the sky, but more of region we've assigned a name to, again, like the sky. The pupil is the area within the iris opening and forms the black part of the eye.

The Crystalline Lens: The lens is a rather complex organ; one that I've had to explain to many patients. Its the first part (front to back speaking) that you cannot see when looking at some one without a special microscope. The lens is also transparent, for light must path through as organized as it entered. It is shaped somewhat like a mentos mint held sideways and can change its shape on command. The brain will send signals to structures in the eye that will actually stretch or relax the lens based on how far or close you want to be able to see.

The Vitreous Chamber: This is another pocket of mainly aqueous and makes up the bulk of the globe. This chamber forms behind the crystalline lens and runs all the way to the inner back wall of the eye, the retina. As before, it is transparent and immune-suppressed allowing light to flow back almost unaltered.

The Retina: This is where all the magic happens! The Retina contains a layer of photoreceptors- little antennae that pick up light and send electric signals to the brain. There are several more types of cells in the retina with complex circuitry that lies beyond the scope of this post. Now imagine a cereal bowl in your hand. Now imagine it with lots and lots of tiny fibers running from every square millimeter. If you took the laser pointer you typically annoy your cat with and directed it into a specific point on this bowl, a fiber would send a signal from the bowl to your computer's central processor. Why you have your computer hooked up to your cereal bowl though is beyond my understanding, nerd. Anyways, your computer is like your brain, and the cereal bowl like your retina. I hope that wasn't too self-defeatingly confusing.

The Optic Nerve: This major structure lies in the same plane as the retina, but travels back beyond the eye. This nerve is basically a large bundle of fibers coming from your retina and heading towards your brain.

If you take one lesson from this long, horrendously boring post, you should understand that the eye consists a complex highly organized system of structures that act together to capture light coming from the world around you in order to code it into electrical signals for your brain to process.

Now that I've read that back to myself, I have a headache. Know that when you are looking into somebody's eye-- all you are doing is looking into a bunch of little organs and shit. Weird when you think how important eye contact is when connecting to people.