ABSTRACT
Seeing is a complex process that begins with the eye and ends in the brain. Of the 12 cranial nerves in the human body, one-third are devoted to vision. In order to see 20/20 with a typical fi eld of view of 160-180 degrees, all parts of the eye and brain must be intact and function fl awlessly. Even the slightest disruption (e.g., disease, trauma, infl ammations) to any one of the parts of the eye or the brain will affect the student’s ability to see clearly. The eyes serve the function of sensory receptors, similar to the sensory receptors located elsewhere on your body. Light rays entering the eye must pass through a very clear and practically dehydrated cornea in order to begin the internal journey through the rest of the eye. The rays bend and move through aqueous fl uid in the front portion of the eye, squeeze through the iris, and then continue through the posterior cave-like portion of the eye, the vitreous chamber and eventually fall on the macula of the retina. But falling on the macula is only half the journey, for it is not only in the eyes where vision occurs. In striking the retina, the light rays cause a chemical disturbance which then converts to electrical synaptic energy. This synaptic energy then moves out the back portion of the eyes through the optic nerve to continue the journey to various regions and interpretation stations of the occipital cortex located in the lower back portion of the brain. When someone states that you must have eyes in the back of your head, they could not be more truthful because it is in the occipital cortex where vision or seeing occurs. With students whose vision is intact, this all takes place in a matter of milliseconds. Think of this complex process as you read this paragraph. As you are reading, you are shifting your gaze continually from left to right/right to left swiftly passing over every black image (letters/words) on this white background (page) while at the same time adjusting for uncontrolled variables such as changes in ambient light and glare, head or body movements away from or toward the page (or monitor), blinking, and even peripheral distractions such as reaching for and
grasping your coffee mug without knocking it over (like I just did!), and you are most likely doing all this while sitting relatively still, not moving. Imagine now a more complex visual task such as driving or playing sports, where the world is continually moving around you and you have to react to these instantaneous changes visually in order to arrive at your destination safely or catch the ball without getting injured. The complexity of the visual task increases when movement occurs.
