INTRODUCTION
Hi one and all. Welcome to our blog!!! Don’t you guys think that it is so pretty and nice? I bet you all do. Anyway, we believed you guys will have an interesting and enriching time when visiting our blog. By visiting our blog, you all will be able to know more about one of our sense organs --- the eye. Over here, we will give you a brief introduction about our wonderful eye and also at the same time let you guys know some interesting facts and viewpoints.
Our amazing sense organ—THE EYE
Have you guys ever wondered how does our eye work? Why can we see things? Well, if you continue reading, you will be able to find out why. Eyes are organs that detect light. Different kinds of light-sensitive organs are found in a variety of animals. In the human eye, light enters the pupil and is focused on the retina by the lens. Light-sensitive nerve cells called rods (for brightness) and cones (for color) react to the light. They interact with each other and send messages to the brain that indicate brightness, color, and contour.
When you look at an object, light rays are reflected from the object to the cornea, which is where the miracle begins. The cornea is a transparent structure found in the very front of the eye that helps to focus incoming light.
Behind the cornea is a colored ring-shaped membrane called the iris. The iris has an adjustable circular opening called the pupil, which can expand or contract depending on the amount of light entering the eye. A clear fluid called the aqueous humor fills the space between the cornea and the iris.
Situated behind the pupil is a colorless, transparent structure called the lens. The lens' job is to make sure the rays come to a sharp focus on the retina. The resulting image on the retina is upside-down. Here at the retina, the light rays are converted to electrical impulses which are then transmitted through the optic nerve, to the brain, where the image is translated and perceived in an upright position!
Ciliary muscles surround the lens. The muscles hold the lens in place but they also play an important role in vision. When the muscles relax, they pull on and flatten the lens, allowing the eye to see objects that are far away. To see closer objects clearly, the ciliary muscle must contract in order to thicken the lens. This is called accommodation.
The interior chamber of the eyeball is filled with a jelly-like tissue called the vitreous humor. After passing through the lens, light must travel through this humor before striking the sensitive layer of cells called the retina. The retina is the innermost of three tissue layers that make up the eye. The outermost layer, called the sclera, is what gives most of the eyeball its white color. The cornea is also a part of outer layer.
The middle layer between the retina and sclera is called the choroid. The choroid contains blood vessels that supply the retina with nutrients and oxygen and removes its waste products. It is pigmented black so as to prevent internal reflection of light.
Embedded in the retina are millions of light sensitive cells, which come in two main varieties: rods and cones. Rods are good for monochrome vision in poor light, while cones are used for color and for the detection of fine detail. Cones are packed into a part of the retina directly behind the retina called the fovea. When light strikes either the rods or the cones of the retina, it's converted into an electric signal that is relayed to the brain via the optic nerve. The brain then translates the electrical signals into the images we see.
Wow, don’t you think that’s amazing? Read up on our various blog posts to know more about the eye! (:
Class Test! :O
Wednesday, March 5, 2008/
11:23 PM
Good morning class, we will be having a biology pop quiz on the eye, yes THE EYE, today! *evil grin* please put away all your books, files, and all related materials and prepare for the test.
*students receive question paper*
*silence*
*stares hard at question paper*
*GULPS*
"ARGHHHHHHHHHHHH!!!!!!" Oww, that was a really loud cry of shock and alarm... Hmmm... Is the biology class test I set really so hard? Why not you try it out too, and see how much you know about the eye! :D
Have fun trying it out! (: Good luck, folks!
rachel [4F/23] --*
Food, Food, Glorious Food!
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10:51 AM
Beware, earthlings. Ever heard of the saying 'You are what you eat' ?
Today, let me, the nutritionist from Planet Good Food(that's me at the top) educate and give you earthlings some tips on how to maintain a good eyesight through the food you eat.
So what type of foods are
EYE HEALTHY?
Studies have suggested that by eating foods rich in six nutrients — antioxidants lutein and zeaxanthin, beta carotene, vitamin C, vitamin E and zinc — you can protect your eyes from disease.
And so you may wonder, what types of food possess these nutrients?
Well,
Most fruits and vegetables are great sources of
Vitamin C, including
ORANGES
GRAPEFRUIT
STRAWBERRIES
PAPAYA
GREEN PEPPERS
TOMATOES
and many more :)
Vitamin E is more difficult to obtain from food sources, since it is found in very small quantities. However, good food sources include
vegetable oils(safflower and corn oil),
almonds,
pecans,
wheat germ...
...and sunflower seeds.
Beta-carotene is present in dark green leafy vegetables (spinach!), deep orange or yellow
fruits and vegetables like
cantaloupe,
mangos,
apricots,
peaches,
sweet potatoes,
carrots,
and fortified cereals.
Lutein and
zeaxanthin are found together in many food sources. Dark green leafy vegetables are the primary sources of lutein and zeaxanthin like
kale,
and collard greens,
but they are also present in lesser amount in other colorful fruits and vegetables, such as
broccoli,
orange peppers,
corn,
peas,
persimmons and
tangerines.
Good food sources of
zinc include
meat,
liver,
shellfish,
milk,
whole grains and
wheat germ(Yes, again).
Eating healthy for your eyes could be the most promising means of protecting your eyes from AMD and cataracts. In addition, planning menus rich in the nutrients described above can mean better overall health for you.
By the way...
Popeye was right about Spinach!By eating the equivalent of one-half cup of cooked spinach four to seven times per week, you can
possibly prevent AMD. Spinach contains a significant amount of lutein. To find out how much of other foods you would need to consume to obtain the same amount of lutein in a 2 cup of cooked spinach, see the equivalency chart below.
Popeye’s Equivalency Table
2 cup of cooked spinach
3 cup cooked kale
2 cup cooked collard or
turnip greens
2 cups of raw spinach
2 cups broccoli
24 cups corn kernels
24 cups Romaine lettuce
22 cups raw zucchini
2w cups canned peas
7 cups green beans
93 cups orange juice
from concentrate
4 pounds of carrots
(that’s a lot of carrots!)
17 cups chopped iceberg
lettuce
Wow! Popeye probably had pretty good eyesight :D
So that's the end of my educating you earthlings for today!
I had better travel back quickly to my Planet now! I still need to attend school tomorrow and the journey is about 5 hours.
Till then,
MUACKS!
(Done by: Wong May Ping 24/4F)
An account of a colour-blindness 'victim'
/
12:30 AM
I was diagnosed with colour blindness, or colour vision deficiency since I was young. It was passed down through the genes, as my father is a 'victim' of colour blindness too, unlike some other friends of mine who are colour blind due to overexposure to certain chemicals or their eyes or brains had suffered damage before. Simply put, it means that I have the inability to differentiate some of the colours that other people can distinguish.
Colour blindness is usually classified as a disability, but I have never found myself in any way inferior to others, or wallowed in self-pity because of it. Admittedly, we do have a disadvantage in some situations, but there are also other selected situations where colour blind people may have advantages over people with normal color vision. I remember when I was younger, my parents tried to explain this deficiency to me. Through the research I did over the Internet, I found out that there are actually some studies which conclude that colour blind individuals are better at penetrating certain camouflages. People who are colour blind may also have a minor advantage in dark vision, but only in the first five and a half minutes of dark adaptation, like in my case.
Colour blindness affects both men and women. The normal human retina contains two kinds of light cells: the rod cells which are active in low light, and the cone cells which are active in normal daylight. Normally, there are three kinds of cones, each containing a different pigment. The cones are activated when the pigments absorb light. The absorption spectrum of the cones vary; one is maximally sensitive to short wavelengths, one to medium wavelengths, and the third to long wavelengths. The absorption spectra of all three systems cover much of the visible spectrum, so it is not entirely accurate to refer to them as "blue", "green" and "red" receptors, especially because the "red" receptor actually has its peak sensitivity in the yellow. The sensitivity of normal color vision actually depends on the overlap between the absorption spectra of the three systems: different colors are recognized when the different types of cone are stimulated to different extents. Red light, for example, stimulates the long wavelength cones much more than either of the others, and reducing wavelength causes the other two cone systems to be increasingly stimulated, causing a gradual change in hue.
The Ishihara colour test, which consists of a series of pictures of colored spots, is the test most often used to diagnose common types of colour blindness, like the red-green colour deficiencies. A number is embedded in the picture as a number of spots in a slightly different colour, and can be seen by those with a normal colour vision, but not by those with a particular colour defect. The full set of tests has a variety of figure/background color combinations, and enable diagnosis of which particular visual defect is present. Most clinical tests are designed to be fast, simple, and effective at identifying broad categories of colour blindness.
There is generally no treatment to cure color deficiencies, however, certain types of tinted filters and contact lenses may aid an individual in differentiating colours better. Optometrists can supply a singular red-tint contact lens to wear in the dominant eye. This may enable the wearer to pass colour blindness tests for certain occupations. The effect of wearing such a device is akin to wearing red/blue 3D glasses and can take some getting used to as certain wavelengths can "jump" out and be overly represented. Additionally, advancements in technology has enabled certain kinds of computer software to be developed to assist those with visual colour difficulties.
Although I may be colour blind, life is definitely no less fulfilling to me! I am still able to see many beautiful things in this world, and I certainly do enjoy doing things like hiking and admiring the breathtaking landscapes on earth. I live by the mission not to allow myself to be pitied, be it by myself or others, and I have never viewed this birth defect as a liability, as I am certainly more fortunate than many others in this world, who sadly are unable to even see. Live life to the fullest, cherish every moment, and life will still be meaningful in its own way, come what may :D
(adapted from http://en.wikipedia.org/wiki/Color_blindness)
rachel [4F/23] --*
