How Do the Eyes Work?

Ladies and gentlemen today I am going to give a basic breakdown of how we see things with our eyes. I will also be touching on the different ways we perceive visual information. Cornea then pupil then lens then retina would be the simplest way for remembering how the eye works. However, I have decided to detail this just a little more so you can all fully understand how the eye literally sees things.

Once light waves have passed through the cornea they enter the anterior chamber passing through the nourishing fluid of the aqueous humor. The light waves are then funneled through the pupil (the black dot in your eye) that is surrounded by the iris. The iris has the ability to change shape to regulate the amount of light going into the pupil. The light will then pass through the lens which also has the ability to change shape in order to focus visual images. Once through the lens light waves pass the posterior chamber and hit the retina.

The retina is made up of light sensitive tissues that contain visual receptors called cones and rods. The rods are the most easily activated because they have a lower threshold than cones. Unlike cones rods do not detect color. Now that you know the basics of how we see things, let's talk about how we perceive what our eyes see.

How we perceive things can differ greatly based on many factors. The way that we perceive visual information is very complex so I am only going to touch on this. For starters once light has activated the visual receptors at the back of the eye information is sent to the brain for processing. Now what I'd like to ask you all is how often you have spent your workday in a blur because you were very tired and could think of nothing else but sleep.

How many times that day did you look at something important to your job and when later asked about it had no idea what they were talking about. This sometimes happens with perception, it can be distorted, and deceptive based on our motives. Another good example of this would be a fan watching a football game. A decision is made about who has possession of the ball after a fumble, but you see what you want to see, you are absolutely positive your favorite player was down before losing the ball. Upon closer inspection the ball was obviously fumbled, why were you unable to see it?

Most likely because your own wants and needs have influenced what you thought you saw. Two other interesting things I'd like to talk about today are shape constancy, and size constancy. Shape constancy means that if an object we are familiar with is flipped around in different positions, presenting different shapes to the retina, we still recognize the object for what it is. Our perception has not changed despite the fact that the shape that the retina sees has. Size constancy similarly helps maintain consistency in the perception of the objects around us.

An example of this would be a remote control car, driven away from us the object seen by the retina would appear smaller, likewise if driven closer the image would appear larger to the retina. Lucky for us we don't perceive size that way; we actually perceive the object moving closer or farther from us.

We are able to perceive things with shape and size constancy based on the background objects. We judge size and shape, using familiar backgrounds for comparison. As you may have noticed these nifty features don't work so well in the instance of a photograph of an unfamiliar object with nothing but darkness for background. In that case it would be very difficult to determine the size, and shape of that object.

We would also be hard pressed to say how far the camera is from the object. Is it a close up or life size? This is a very basic and simplified version of some key features of perception. The components of our eyes are both delicate and very complex; consider in your day to day activities just how much information your brain receives via your eye's perception. It is little wonder that we as humans place such extraordinary value on our eyesight.