See the Blood Vessels in Your Eye

Description: Students will see their own retinas

Purpose: To locate and identify the layer of blood vessels in the retina

Length of Activity: 20 minutes

Materials:

• A mini flashlight or pen light.
  
  
• A room which you can darken, ambient or dim light is fine.
  
  
• A sheet of black construction paper.
  
  
• Eye protection such as goggles with clear lenses (recommended).

Steps:

1. Darken the room. Turn off the lights and close the shades, if possible. Dim light or ambient light is fine.

2. Put on eye protection or goggles, if using.

3. In one hand hold the black sheet of construction paper in front of your face so that the paper fills your field of view.

4. In the other hand, hold the mini flashlight or pen light in front of one eye, about ½ inch in front of and slightly below the center of the pupil. Be careful not to poke yourself in the eye!

5. Turn the flashlight or pen light on and move it slowly from side to side a short distance, about a ¼ inch. Do not move your eye or follow the motion of the light.

6. Keep doing this for 20 seconds. Notice the pattern that appears. It will look like the branches of a tree or the branching of a river viewed from high above.

What’s Going On?

You can use a dim point of light to cast a shadow of the blood supply of your retina. This will allow you to see the blood supply of your retina, and even your blind spot. The pattern you see are the arteries and veins that supplies blood to your retina. It spreads out from the dark area called your blind spot. When you exercise, you are increasing circulation and driving oxygen here. In the retina, the blood supply is the top layer. Your light is causing a shadow from the blood supply layer to the other layers underneath. As you move the point of light, the shadow moves, making it visible to you. Normally, there would be no shadow and your brain would ignore seeing the blood supply.