How the eye works by Leslie Samuel

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Watch this vivid and clear explantion of how the eye works.

Why can't we look at the sun?

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We have been told since young not to look directly at the sun, especially during solar eclipses. Discovery News explains why.



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360 degree stereoscopic vision is the answer

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Why do humans, owls and tigers have forward facing eyes? Deer, cows, and antelopes have eyes on the sides of their faces?

The answer: Stereoscopic vision is important for hunters; a wide field of vision is important for herbivores to detect and escape from their predators

When both eyes face forward, the fields of vision of the two eyes will overlap. This gives rise to a sensation of depth or distance. This is important if a predator is to catch its prey. Hunters need this acute sense of distance/depth.

In the case of prey animals, their food organism does not run away. (Plants are rooted to the ground.) However herbivores have to be on the look out for the predators and hence the importance of a wide field of vision.

Then the question is why do hammer-head sharks have eyes which are so far apart that it does not seem to give them stereoscopic vision. BTW, these sharks are avid hunters that chase and catch fast swimming and agile prey such as squids and ray fish.

To find out more on this click Why the hammerhead shark got its hammer


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Repair our eyes and do it cheaply and safely?

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I found a fascinating article that will interest most of us in Singapore, given the prevalence of myopia or short-sightedness here.

It is about restoration of good eye-sight using stem cells. It take less than a month to restore sight. It is cheap, non-invasive, only takes a couple of hours to complete.

Sounds too good to be true. The new procedure has been performed in Sydney, Australia. Scientists think this technique can be used in skin grafts as the cornea is the skin of the eye. It has the same physiological functions as other skin.

Watch the video below to 'see' for yourself.



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Lesson 27: Sense organs

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More on the nervous system and the eye. Please remember that only the eye and skin are in the syllabus now. The other sense organs are still very interesting, but they will not be tested in the exams.

This set of slides contain the following:

• sense organs eye and skin, and nervous system and reflex actions
• stimulus, receptor, coordination, effector, response sequences
• nerve cell, labels, annotation
• how synapse works
• pupil reflex, blink reflex, cough reflex
• labels in reflex actions, annotated diagram
  
• eye, labels, annotations
• compare eye with camera in its functions
• short and long-sightedness
  
• short questions
  

Remember not to dwell too much on the ear, tongue, nose, other parts which will not be tested in your examinations.

Unit 5 Nervous System And The Senses

View more OpenOffice presentations from Dr samuel Aylward.

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