You're Blind!!....Well sort of (Ryan Hendrickson)

Author

Ryan Hendrickson

Principle(s) Illustrated

1. Anatomy of the eye

2. Photoreceptors

3. The optical nerve

Standards

• 1.1.1 - Science Standard

• 1.1.2 - Science Standard

• 1.1.3 - Science Standard

Questioning Script

Prior knowledge & experience:

Basic anatomy of the eye,

Root question:

What happen if you close your left eye and stare at the cross mark in the diagram with your right eye while moving toward or away from the screen?

Target response:

The dot should disappear when the dot falls in the "blind spot: of the eye.

Common Misconceptions:

The only blind spot humans deal with everyday is the blind spot of a car.

Photographs and Movies

1. Close your left eye and stare at the cross mark in the diagram with your right eye. Off to the right you should be able to see the spot. Don't LOOK at it; just notice that it is there off to the right (if its not, move farther away from the computer screen; you should be able to see the dot if you're a couple of feet away).

2. Slowly move toward the computer screen. Keep looking at the cross mark while you move. At a particular distance (probably a foot or so), the spot will disappear (it will reappear again if you move even closer).

Why does the spot disappear?

The spot disappears because it falls on the optic nerve head, the hole in the photoreceptor sheet.

So, as you can see, you have a pretty big blind spot, at least as big as the spot in the diagram. What's particularly interesting though is that you don't SEE it. When the spot disappears you still don't SEE a hole. What you see instead is a continuous white field (remember not to LOOK at it; if you do you'll see the spot instead). What you see is something the brain is making up, since the eye isn't actually telling the brain anything at all about that particular part of the picture.

Eye Dominance Chart

References

Seeing More Than Your Eye Does (link)