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Senses 2 hours module

Functions of the eye

The human eye functions much like a digital camera. Both devices gather, focus, and transmit light through a lens to create an image of the surrounding environment. In order to see, we must have light.

  1. Light enters the eye through the cornea, the clear front surface of the eye, which acts like a camera lens.
  2. The iris of the eye functions like the diaphragm of a camera, controlling the amount of light reaching the back of the eye by automatically adjusting the size of the pupil, which acts like an aperture. In dark conditions, the pupil widens. In bright conditions, the pupil constricts.
  3. The eye's crystalline lens, located directly behind the pupil, helps the eye automatically focus on near and approaching objects, like an autofocus camera lens.
  4. The light then travels through the vitreous humor, a clear gel-like substance that fills the middle of the eye.
  5. Light then reaches the retina, a sensitive inner lining of the back of the eye. The retina acts like camera film, converting optical images into electronic signals.
  6. The image reflected on the retina is upside down. The optic nerve transmits signals to the visual cortex in the brain, which flips the image right side up and creates one composite image.

 

Perception, Color, and Image

The eye’s retina contains millions of tiny light-sensing nerve cells called rods and cones, which are named for their unique shapes.

Eye’s retina comprised of nerve cells
  • Cones are responsible for perceiving color and detail.
  • Rods and responsible for night vision, peripheral or side vision, and detecting motion.

Rods and cones convert the light from our retinas into electrical impulses, which are sent by the optic nerve to the brain, where an image is produced. The central part of the retina, called the macula, is about the size of a pencil eraser. It is this small area that gives us central vision needed for activities like reading, driving, and working on the computer.

Tears

Tears

Another function of the eye is to produce tears. Tears are actually an important component of maintaining vision, because they nourish and lubricate the surface of the eye as well as wash away debris. A normal tear consists of water, oil and mucus. If there’s a disturbance of the tear film, people will often experience tearing, burning, irritation or blurred vision.

There are three main parts in the tear system:

  1. Glands that make the tear fluid, oil and mucus
  2. Openings that let tears flow out of the eye
  3. Ducts inside the nose that tears drain through

When functioning properly, the tear system of the eye keeps the eye wet enough to be comfortable without overflowing. Too much tearing could indicate a problem with tear production or drainage. Some people's eyes do not produce sufficient quality or quantity of tears, causing the condition dry eye.

But... how is the visual process?

https://www.youtube.com/watch?v=Wx1bgW3eFEk

 

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