Anatomy And Physiology

How does Vision Work



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Looking around, we see so many different shapes and colors. Vision is one of the most important senses out of the known five, we use to obtain information. After some getting used to, we sometimes forget how great a gift sight really is, unless it is all or somewhat lost.

It takes seven different major parts of the eye for our minds to create images: The iris, pupil, cornea, sclera, retina, the optical nerve and the lens.

The iris is the colored portion of the eye in charge of deciding how much light to let in for maximum comfort. You get the color of your eyes from your parents in your genetics. The iris is a pigmented tissue called stroma. For the iris to dilate, it retracts and unretracts. The iris dilates when:

-The adrenaline starts pumping so someone can see better to fight or run away.

-A person is trying to get a better look at something.

-A person is nervous or lying.

-It's dark.

The cornea is the transparent substance made of cells and protiens that cover the eye and protects it from any irritants that may get into it such as dust or dirt. Unlike tissues in the body, the cornea has no blood vessels to nourish it. Instead, it gets its nourishment from the tears that are secreted into the eye behind it.

The sclera, also known as the white part of the eye, is behind the cornea, and plays a protective roll in keeping the eye safe. The sclera is made up of collagen and fibrous tissues. Although in the average human, the sclera is white, small children's scleras are thinner and can appear more blue. The fat cells can collect in the scleras of older people, making their scleras look yellow and discolored.

The lens is the part of the eye that helps refract light like the cornea. The lens changes shape, so we can focus on close and far objects.

The optical nerve is a bundle of more then 1 million fibers intertwined together. It connects to the retina and is necessary for good sight.

The retina is the tissue lining of the inner part of the eye that is light sensitive. This part of the the eye receives messages from the lens, and sends the information (pictures) to the brain right side up.

All of these parts working together produces vision. When looking at something, the iris adjusts the pupil to best suited light, then the lens refracts the light image upside down, which is then picked up by the retina. The information is then sent to the brain right-side up.

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