Wednesday, June 5, 2013

Understanding How Eyes Work

Every day you look at objects, people, colours, words, numbers which all help you to understand the world. You might not often think about how your eyes work but they are an essential part of how we carry out our daily activities.

The eyes work like small round machines constantly working to help us see things. They are made up of little parts which work together and send messages to the brain. Light bounces off objects into our eyes to allow us to see them. 
Childs eyes
What’s what?


The bits you can see: An eye is made up of several different parts. The parts you can see are the pupil (the black dot in the centre), the iris (the coloured area surrounding the pupil) and the sclera (the white area around the iris). These parts are all enclosed by your eyelids which are rimmed with eyelashes to filter out any nasty dirt or grime before it harms your eyes. In the corner of your eyes are your tear ducts. These are in charge of releasing tears to keep your eyes clean and to cry when you’re feeling sad!

The pupil acts as a little shutter to decide how much light enters your eye. If it is a very bright day, your pupils will contract (get smaller) to allow less light in. In darkness, your pupil will dilate (get bigger) to get as much light into your eye as possible. [Handy tip: Try looking at your cat’s eyes in daylight and then again when it gets dark to see how they change!]

The bits you can’t see: Over the front of your eye is a clear layer called a cornea. This layer is completely clear to allow light to pass through and reach the back of your eye where it can be sent to the brain to be processed.

At the back of your eye, there is a delicate layer called a retina (about the size of a postage stamp) which is made up of tiny cells. These cells are called rods and cones. The cone cells are found in the centre of the retina and help us to see things sharply and clearly. Rod cells are around the edge of the retina and help us to see things moving and in dim light. For example, imagine looking at a car parked outside your house. The cone cells help you to clearly see the shape of the car, the colours and windows etc. Next, imagine the car moving down the road at night. This is when the rod cells start to work. They help you to see the car in motion in the darkness.

These cells collect light signals and send them to the optic nerve, almost like a relay race. The optic nerve receives the signals and sends them to the brain to be processed and allow us to understand what we see.


Interesting facts you might not know:
1.    When an image is projected on the back of your retina, it is upside down! The optic nerve sends the signals to the brain where it is turned the right way up.
2.    All babies are born with blue eyes- ask your parents! This is because other colours such as brown and green take longer to develop. By the time you’re 6 months old, your eyes will have reached their final colour.
3.    You blink around 12 times a minute! You won’t even notice you do it but blinking helps to keep your eyes clean and moist to protect them from dust and dirt. 

It’s useful to understand how eyes work because they are an essential part of how we function every day.


Featured images:
  •  License: Royalty Free or iStock source: http://office.microsoft.com/en-us/images/results.aspx?qu=eyes&ex=2#ai:MP900423034|mt:2|

Victoria is a blogger for glasses frames website, DirectSight.

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