The HUMAN EYE
The human visual system, shown above is an extremely complex organ, which allows humans to see. The shape of the human eye is specifically adapted so it only allows light to enter through the pupil. More specifically it is a sphere, which only allows light (photons) through the pupil, via the lens, and on to the retina, located at the back of the eye. Although this is a very generalised input to output, there are many more complicated processes along the chain. The anatomy of the eye again is quite complex, however it can be easily broken down into several parts. Working from the outside inwards, there are three distinct layers. Aehlert and Vroman (2010) states that “these layers include the fibrous tunic, which consists of the sclera and cornea; the vascular tunic, which consists of the choroids, ciliary body, and the iris; and the nervous tunic, which contains the retina” (p189). Effectively, the eye is a piece of art; without it, life would be visually dull.
Jonathan.
Jonathan.
The VISUAL CORTEX
“It may be a mistake, however, to think of the eye as an outgrowth of the brain as is popularly suggested. It would be more accurate to think of the brain, or at least part of it, as an evolutionary extension of the eye” (Worthy, 1999, p71). For any argument, there should always be both sides, to which I personally can understand in the quote above. I believe that the general public would assume that the eye is an outgrowth of the brain, for the simple reasons that the eyes are smaller than the brain and that the brain has no control over our sight. However, it is the latter of the quote, in which I tend to agree with. The way, in which the human eye sends out the electric signals via the optic nerve, into the visual cortex of the brain is extremely remarkable.
The visual cortex can be split up further into 5 layers. These are V1, V2, V3, V4 and V5. In some instances, the V1 maybe referred as the primary visual cortex. It is in the primary visual cortex that the image we have seen with our eyes is processed correctly. The retina passes the electrical signal via the optic nerve via all the other visual pathways, as shown in the image above, to the primary visual cortex. In all cases of seeing an object, the image will always be inverted, back to front and blurry. The sheer amount of processing power the brain has to be able to correct the image, so we see correctly makes me wonder how humans would survive without it. However, with that said, there are humans who exist who are completely blind and are still able to live their daily life.
The visual cortex can be split up further into 5 layers. These are V1, V2, V3, V4 and V5. In some instances, the V1 maybe referred as the primary visual cortex. It is in the primary visual cortex that the image we have seen with our eyes is processed correctly. The retina passes the electrical signal via the optic nerve via all the other visual pathways, as shown in the image above, to the primary visual cortex. In all cases of seeing an object, the image will always be inverted, back to front and blurry. The sheer amount of processing power the brain has to be able to correct the image, so we see correctly makes me wonder how humans would survive without it. However, with that said, there are humans who exist who are completely blind and are still able to live their daily life.
I have been able to gather that the human eye is much like a camera, but it has so much more power and flexibility as compared to the human eye. The eye can expose difficult scenes, enabling the human to see accurately, unlike a camera, which cause difficulty with backlit scenes. The visual cortex plays a major factor for us to be able to see, however if any visual nerves breaks down or a tumour presses against it, then our field of vision will be automatically reduced.
Jonathan.
Human Eye – Access Research Network., (n,d). Labeled side view of the human eye. [online image] Available from: http://www.arn.org/docs/glicksman/100104%20fig1.jpg [Accessed 5 March 2014].
Aehlert, B. and Vroman, R., (2010). Paramedic practice today. St. Louis: Mosby Jems Elsevier.
Worthy, M., (1999). Eye Color: A Key to Human and Animal Behavior. San Jose: ToExcel.
Visual Pathway – Edoctoronline., (n,d). Labeled side view of the human visual pathway. [online image] Available from: http://www.edoctoronline.com/media/19/photos_6F6DC7DF-28FE-433F-9AED-2CB301F35C4B.jpg [Accessed 5 March 2014].