The sense of sight

The eye is the sense organ of sight. You see with your eyes. Your eyes work like a very good camera. They can take pictures that are still or moving, in color or in black and white, and from a distance or close up. Of course, your eyes are better than a camera! In this text you will learn how your eyes work and how you see.

The eye is made up of different parts: the iris, pupil, eyelid, and retina. The iris is a muscle. It is the part of the eye that lets in the right amount of light. The big, colored circle in the center of the eye is the iris. Pigment gives the iris its color. The color of the iris is different in different people.

In the center of the iris there is a hole that lets in the light. This hole is the pupil. The iris muscle can change or adjust the size of the pupil. The pupil will enlarge if the light is dim and get smaller when the light is bright.

The eyelid is another important part of the eye. It has two important functions. The eyelid controls the amount of light enters the eye. When you want to keep out light, you can lower you eyelid. Also, raising and lowering the eyelids helps keep the eyes moist.

Another important part of the eye is the retina. The retina is the part of the eye that receives the image and focuses the light. A picture forms on the retina in the back of the eye. The image on the retina is upside down. How does the image get right up, so you see normally?

Light enters through the pupil in the eye and is received by the nerves in the retina. When the nerves in the retina receive the light, they send a “picture message” to the brain. This picture message is upside down. The brain changes the message into a right-side-up picture. The brain performs a very important function in the sense of sight.

Sometimes people need glasses because they can not focus the light properly. The picture is not clear. Three of the most common eye problems are being nearsighted, farsighted or having an astigmatism. If you are nearsighted, you can see things clearly only if they are very near. If you are farsighted, you can see things clearly only if they are far away. If you have an astigmatism, things look blurry whether they are near or far. All three problems can be corrected with eyeglasses or contact lenses. They help focus the light properly so that you can see clearly all the time.

VII. Answer the following questions:

1. What is the function of the iris?

2. When does the pupil change size?

3. Name two important functions of the eyelid.

4. On which part of the eye does a picture form?

5. How does the brain help you to see?

6. Name common eye problems.

7. How can eye problems be corrected?

VIII. Ask 3-4 questions on this text to your group mates.

IX. Put the sentences in the order they met in the text.

1. The eye is made up of different parts: the iris, pupil, eyelid and retina.

2. The eyelid is another important part of the eye.

3. The image on the retina is upside down.

4. The big, colored circle in the center of the eye is the iris.

5. Raising and lowering the eyelids help keeps the eyes moist.

6. A picture forms on the retina in the back of the eye.

7. The brain changes the message into a right-side-up picture.

8. Three of the most common eye problems are being nearsighted, farsighted or having an astigmatism.

9. All the problems can be corrected with eyeglasses.

10. Sometimes people wear glasses because they can not focus the light properly.