The Sense of Sight by Karan, Steph, Lesley, Wendy & Jeannie

THE INCORRECT INFORMATION
Our initial thought was that for sight to occur, it mainly depended on the cornea, which was located at the back of the eye and responsible for processing the image we see. It flipped the image upside-down, and then passed it along to the brain. In fact, it is the retina, partnered with the optic nerve, that does this function. We had also excluded the important role of light during the act of seeing, as well as neglected various parts of the eye.

DETAILED DESCRIPTION OF SIGHT
Eyes are often compared to have the same functionality as a camera would. The camera as we know it, uses lens and film to produce an image taken within its visual field. The same concept can be applied to the eye. Light first enters through the cornea, a clear tissue in the front of our eyes, which then passes through our pupils. The pupils are similar to the lens or the shutter of a camera in that it directs how much light enters our eyes. The pupils would widen when it is dark to allow more light in and shrinks when there is an excess of light. Surrounding the pupil is a coloured ring called the iris, which is a muscle fibre that helps the pupil change size. When we look at an object, the light enters through the pupil which is then focused on the retina (back of the eye) via the pupil and the cornea. The retina is referred to as the film of the camera. This retina is what captures the image in our visual field. The retina is usually lined with photoreceptors , which change light rays into electrical impulses which are then sent to the brain through the optic nerve.

The optic nerves are connected to the optic chiasma where the inner (nasal) half of each retina crosses to the opposite side, and the outer (temporal) half stays on the same. Like other sensory and motor projection systems in the body, each side of the body is represented by the opposite side of the brain. The optic chiasma leads to the visual cortex where there is a projection area in each hemisphere containing a "map" of visual space. What the retina reads will be mapped on the projection area, and thus vision occurs. In other words, the images we see are flipped upside down and are then flipped right side up when it is received in our brain.

BIBLIOGRAPHY

• Diagram I courtesy of MedlinePlus
• Diagram II courtesy of Karan Patel
• http://www.accessscience.com
• http://www.aoa.org/
• http://health.yahoo.com/vision-videos
• http://www.howstuffworks.com/eye.htm
• http://www.pasadenaeye.com/
• http://www.sightsavers.org
• Steve Parker, The Human Body, Eyes and Vision: The Sequence of Vision, First American Edition, 2007, 92-93.