Select Special Senses

Select Special Senses

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Exercise 3: The Blind Spot - Vision

Go through the boxes below, starting with this top box and work through the blind spot testing.

One of the most dramatic experiments to perform is the demonstration of the blind spot. The blind spot is the area on the retina without receptors that respond to light. Therefore an image that falls on this region will NOT be seen. It is in this region that the optic nerve exits the eye on its way to the brain. To find your blind spot, look at the image below or draw it on a piece of paper:

To draw the blind spot tester on a piece of paper, make a small dot on the left side separated by about 6-8 inches from a small + on the right side. Close your right eye. Hold the image (or place your head from the computer monitor) about 20 inches away. With your left eye, look at the +. Slowly bring the image (or move your head) closer while looking at the +. At a certain distance, the dot will disappear from sight...this is when the dot falls on the blind spot of your retina. Reverse the process. Close your left eye and look at the dot with your right eye. Move the image slowly closer to you and the + should disappear.

Here are some more images that will help you find your blind spot.

For this image, close your right eye. With your left eye, look at the red circle. Slowly move your head closer to the image. At a certain distance, the blue line will not look broken!! This is because your brain is "filling in" the missing information.

This next image allows you to see another way your brain fills in the blind spot. Again, close your right eye. With your left eye, look at the +. Slowly move your head closer to the image. The space in the middle of the vertical lines will disappear.

In the next two images, again close your right eye. With your left eye, look at the numbers on the right side, starting with the number "1." You should be able to see the "sad face" (top image) or the gap in the blue line (bottom image) in your peripheral vision. Keep your head still, and with your left eye, look at the other numbers. The sad face should disappear when you get to "4" and reappear at about "7." Similarly the blue line will appear complete between "4" and "7."

Here is another image to show your blind spot. Close your right eye. With your left eye, look at the +. You should see the red dot in your peripheral vision. Keep looking at the + with your left eye. The red dot will move from the left to the right and disappear and reappear as the dot moves into and out of your blind spot.

*adapted from - Washington University Senses Lab

Comments or suggestions feel free to let me know -- Gary Glaser -- gwglaser@genesee.edu