Lesson 4: Communication with the Outside World Preface

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Lesson 2.4: Communication with the Outside World


Our senses allow us to communicate with the outside world. What we smell, hear, taste, touch and see direct our actions. But it is vision that dominates our impressions of the outside world. We use this sense every moment when we are awake and we even dream in visual images while we sleep. We blink. We stare. We cry. Our eyes not only interpret and respond to what we see, but they allow us to communicate our feelings and emotions.

Human vision is a combination of “seeing” with the eye and “perceiving” with the brain. The eye has the remarkable ability to convert light into a stream of nervous impulses. Various structures in the eye focuses light on the retina and neurons then take information about this image to the brain for processing and interpretation. Each structure in the eye plays a unique role in assuring that the image you see is the image before you.
In this lesson, students will examine the structure of an eye by completing an eye dissection. They will investigate the many aspects of visual perception by completing station exercises and by interpreting results for tests in visual acuity, depth perception, peripheral vision, color vision, accommodation, optical illusions and afterimages. Students will use an eye model to investigate the function of the lens in the eye and will use this model to explore the power of corrective lenses. Students will also be asked to “put themselves in someone else’s eyes.” They will research the science behind vision disorders as well as demonstrate what sight would be like for these individuals. Lastly, students will describe the tests and procedures that go into a routine eye exam, as well as compare three different career paths in the field of vision. This lesson will help stress the role of the senses, particularly sight, in allowing us to communicate with the world and allowing the world to communicate with us.


  1. The structures within the human eye work to focus and process light.

  2. The eye allows perception of color, depth, brightness, and optical illusions.

  3. Errors in the structure and function of the eye can lead to problems in acuity or dysfunction.

  4. Problems with focusing light in the eye can be corrected with lenses.

Knowledge and Skills

It is expected that students will:

  • Identify the key structures of the eye.

  • Demonstrate how light is processed in the eye in a person with normal vision, as well as a person with myopia or hyperopia.

  • Explain the tests and procedures in a typical eye exam.

  • Diagram the path of light as it enters the eyes and travels to the brain for processing.

  • Evaluate visual perception by testing depth perception, peripheral vision, color vision, and visual acuity.

  • Experiment with lenses to refocus light and correct problems with vision.

Essential Questions

  1. How do humans communicate with the world around them?

  2. How does the power of sight allow humans to communicate with the outside world?

  3. How is light focused by the eye?

  4. How do the eye and the brain work together to process what we see?

  5. How does what we see impact other human body systems?

  6. What is visual perception?

  7. What does it mean to have 20/20 vision?

  8. How can corrective lenses be used to refocus light and resolve myopia and hyperopia?

  9. How does the eye perceive depth, color and optical illusions?

  10. How does an error in the structure or function of the eye relate to disease or dysfunction?

  11. How is life impacted by a vision disorder?

  12. What are the tests and procedures in a routine eye exam?

Key6.2 Terms


The automatic adjustment of the eye for seeing at different distances affected chiefly by changes in the convexity of the crystalline lens.


A defect of an optical system (as a lens) causing rays from a point to fail to meet in a focal point resulting in a blurred and imperfect image.

Blind spot

The small circular area in the retina where the optic nerve enters the eye that is devoid of rods and cones and is insensitive to light.


Any of the conical photosensitive receptor cells of the vertebrate retina that function in color vision.


The transparent part of the coat of the eyeball that covers the iris and pupil and admits light to the interior.

Depth Perception

The ability to judge the distance of objects and the spatial relationship of objects at different distances.


A condition in which visual images come to a focus behind the retina of the eye and vision is better for distant than for near objects -- called also farsightedness.


The opaque muscular contractile diaphragm that is suspended in the aqueous humor in front of the lens of the eye, is perforated by the pupil and is continuous peripherally with the ciliary body, has a deeply pigmented posterior surface which excludes the entrance of light except through the pupil and a colored anterior surface which determines the color of the eyes.


A curved piece of glass or plastic used singly or combined in eyeglasses or an optical instrument (as a microscope) for forming an image by focusing rays of light.


A condition in which the visual images come to a focus in front of the retina of the eye because of defects in the refractive media of the eye or of abnormal length of the eyeball resulting especially in defective vision of distant objects -- called also nearsightedness.

Optic nerve

Either of the pair of sensory nerves that comprise the second pair of cranial nerves, arise from the ventral part of the diencephalon, form an optic chiasma before passing to the eye and spreading over the anterior surface of the retina, and conduct visual stimuli to the brain.


The opening in the iris, which admits light into the interior of the vertebrate eye; muscles in the iris regulate its size.


The deflection from a straight path undergone by a light ray or a wave of energy in passing obliquely from one medium (as air) into another (as water or glass) in which its velocity is different.


The sensory membrane that lines most of the large posterior chamber of the vertebrate eye, is composed of several layers including one containing the rods and cones, and functions as the immediate instrument of vision by receiving the image formed by the lens and converting it into chemical and nervous signals which reach the brain by way of the optic nerve.


Any of the long rod-shaped photosensitive receptors in the retina responsive to faint light.

© 2009 Project Lead The Way, Inc.

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