The optic nerve is connected to the brain. Our eyes see the object or image, and our brain interprets it. Side-view mirrors on cars are a good example of how we compensate for our blind spots.
Many times, cars traveling next to us fall in our blind spot, and the side-view mirrors give us a different angle to view the same area. A recent study found that certain eye exercises can help reduce the size of the blind spot, but more research is needed.
If one eye is trained, these gains did not transfer to the other untrained eye. Each of our eyes has a tiny functional blind spot about the size of a pinhead. In this tiny area, where the optic nerve passes through the surface of the retina, there are no photoreceptors. Since there are no photoreceptor cells detecting light, it creates a blind spot.
Without photoreceptor cells, the eye cannot send any messages about the image to the brain, which usually interprets the image for us. Typically, the blind spot is nothing to worry about. It occurs naturally and serves a purpose. However, if you notice that your blind spot is getting larger, or if you have other blind spots in your field of vision, or floating blind spots, these are not normal, and should be evaluated by an eye doctor.
From your plots on the computer screen, calculate the distance of the optic nerve head the Blind spot from the fovea as it really is in your eye. Use in your calculations the average diameter of the measured blind spot on the screen, the distance of subject from screen, and an average optical length of the eye of 1.
Then calculate the size of the optic nerve head from your plotting of the blind spot. The following figure shows you how to do it. It illustrates how you can calculate the distance from the fovea to the blind spot in your eye. Here's the logic underlying the figure: - You have projected this distance from your eye, forward on to the computer screen — there you fixated on a spot i. In this simulation you will estimate the size of your blind spot by finding the biggest possible ellipse that is invisible to your right eye.
Close or cover your left eye and place your right eye directly in front of the plus sign. Move your head in a straight line towards and away from the screen to find the point where the red circle disappears. Confirm that this is the right position by moving your head towards the screen until the circle reappears, and back away from the screen until the circle disappears. Use this as the optimal viewing distance and position.
With your head at the optimal viewing distance, close or cover your left eye and with the right open eye, fixate on the cross. Use the keyboard arrows: to change the position of the red circle. If you move the red ellipse to the right edge of the square and then move it horizontally to the left, you should see it disappear into your blind spot and then reappear on the other side!
Same if you move it up and down at the correct horizontal location. Place the red ellipse approximately in the center of your blind spot, both in the horizontal and vertical directions this doesn't need to be exact, you can correct the position later. Once the position is about right, use the letters z and x: to change the height, and the letters a and s: to change the width. Progressively increase the size of the ellipse until the edges only just become visible.
If all edges are visible, you might experience "filling-in", because the blind spot is surrounded by the red edges of the ellipse your brain will fill in the blind spot with red and you will "see" the whole red ellipse! Decrease the size to one size smaller, such that the edges are only just NOT visible. The red ellipse should be located on the screen such that it's the biggest possible, while still being completely invisible!
Measure the width and height of the ellipse on the screen and use the method of equal triangles described in the "Analysis" tab to infer the size of the blind spot on your retina. Remember to stay at the optimal viewing position at all times, to keep your head still and to fixate as well as possible.
Any change in head or eye position will make the blind spot move, and the red circle reappear! Use the keyboard arrows to change the center location of the circle. Materials: Blind spot testers: make your own or download a template of 11 testers. More lots more about Blind Spots Read about the eye. Calculate the Diameter of Your Blind Spot. An octopus does not have a blind spot! The retina of the octopus is constructed more logically than the mammalian retina.
The photoreceptors in the octopus retina are located in the inner portion of the eye and the cells that carry information to the brain are located in the outer portion of the retina. Therefore, the octopus optic nerve does not interrupt any space of retina. Octopus Eye Image courtesy of Biodidac. Make colors appear using only black and white!
Make your own Benham Disk. Depth Perception - I For grades K Two eyes are better than one, especially when it comes to depth perception. Depth perception is the ability to judge objects that are nearer or farther than others. To demonstrate the difference of using one vs. Hold them either vertically or horizontally facing each other at arms-length from your body.
With one eye closed, try to touch the end of the pencils together. Now try with two eyes: it should be much easier. This is because each eye looks at the image from a different angle. This experiment can also be done with your fingers, but pencils make the effect a bit more dramatic. Materials: Pencils but your fingers make a good substitute.
Drop IT! Collect a set of pennies or buttons or paper clips. Sit at a table with your subject. Put a cup in front of your subject. The cup should be about two feet away from the subject.
Hold a penny in the air about 1. Move the penny around slowly. Ask your subject to say "Drop it! When the subject says "Drop it," drop the penny and see if it makes it into the cup.
Try it again when the subject uses both eyes. Try it again with the cup farther away from the subject. Try it again with the cup closer to the subject. Compare the results of "10 drops" at each distance. Questions: Is there improvement with two eyes? Is there improvement with the cup is closer to the subject?
The actual dimensions of the circles are not too important and you don't have to color the circles. Place the target on the ground about five feet in front of you.
Have a friend stand near the target. Have your friend hold out an ink marker with the tip pointing down. Close one eye. Tell your friend to move forward or backward or side to side until you think the marker would hit the center of the target if it was dropped. Tell your friend to drop the marker when you think the marker is over the target center. The marker should leave a spot where it hit the target.
Try it 10 times with one eye closed and add up the "score" for the 10 drops. Now try it with both eyes opened get a different color marker when you use 2 eyes to see the difference on the target. Is your score better when you use two eyes? Materials: Paper for target Markers two colors.
Shifting Backgrounds, Shifting Images For grades K Here's another way to demonstrate how different images are projected on to each eye. Look at an object in the distance feet away , such as a clock on the wall. Close one eye, hold up your arm and line up your finger with the object. Now without moving your finger or your head, close the opened eye and open the closed eye. The object in the distance will appear to jump to the side This shows that different images fall on each eye.
Materials: NONE. Dark Adaptation For grades There are two types of photoreceptors in the eye: rods and cones. The rods are responsible for vision in dim light conditions, the cones are for color vision. To demonstrate how the photoreceptors "adapt" to low light conditions, get a collection of objects that look slightly different: for example get 10 coke bottle caps, 10 soda bottle caps, and 10 water bottle caps. They should feel the same, but not look the same.
In a bright room, ask students to separate the caps into piles of similar caps. Then turn off the lights so the room is very, very dim. Ask them to separate the caps again. Turn off the lights and look at the results Count the number of errors.
The technical explanation for dark adaptation is not necessary for small children. Plan to talk and discuss for about minutes After the discussion minutes , ask the students to separate the caps again in the same very, very dim conditions as before. There should be fewer errors this time because the photoreceptors have adapted to the low light conditions.
Materials: Three sets of bottle caps or other similar items. Visual Illusions Grades Many of these illusions are available as interactive shockwave games in the Neuroscience for Kids Gallery of Visual Illusions. What you see is not always what is there. Or is it? The eye can play tricks on the brain. Here are several illusions that demonstrate this point. The Magic Cube Look at the center cube.
What side is the front? Is the front as shown on the cube on the right side or is the front as shown on the cube on the left side or is there no front at all?
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