why do we have blind spots in our eyes
The human eye is pretty good at accurately detecting and enormous array of information about the world around us, but it does have its limitations. One example of this is a blind spot or a small portion of the visual field that corresponds to the location of the optic disk located at the back of the eye. The blind spot is the location on the
known as the optic disk where the optic nerve fiber exit the back of the eye. Why Do We Have a Blind Spot? The optic disk is approximately 1. 5 millimeters or 0. 06 inches in diameter. In addition to being the point where the optic nervePexits the eye, it is also where the major blood vessels enter to provide blood flow to the eye. Because there are no cones or rods at this point on the retina, there is a very small gap in the visual field. You literally have a very tiny gap in your vision where you are essentially blind. Why Don t We Notice the Blind Spot? While there are ways to force yourself to notice this blind spot, we typically do not notice this visual gap in our day to day lives. Why? have proposed a number of different explanations as to why we do not notice this blind spot. Some suggest that the opposite eye compensates for the missing visual information. This suggests that when both eyes are open, the visual fields overlap and fill in the missing information for the opposite eye. One of the most commonly accepted theories is that the actually fills in the missing information using visual cues in the environment.
Even if you close one eye, the blind spot is almost impossible to detect. This is because your brain is so adept at providing the missing visual information so that you never notice that small gap in your visual field. If you would like to actually notice your own blind spot, you can see the phenomenon in action in this blind spot demonstration. Can You Shrink Your Blind Spot? Surprisingly, researchers have found that you might actually be able to shrink your blind spot by using certain eye training exercises. In a small study involving just 10 participants, researchers found that using specific eye exercises could shrink the blind spot by as much as 10 percent. The exercises used in the study involved placing an image of a small ring directly in a person s blind spot and displaying waves of light and dark bands moving through the ring. The participants were asked to determine which way the bands were moving as well as the color of the ring. The size of the ring was manipulated so that at the beginning of the study, it was detectable about 70 percent of the time, then the researchers modified the size so that it was eventually so small it was completely hidden by the blind spot. Over time, the participants were better able to detect the smaller image in their blind spot as well as judge the color of the ring and direction of the moving bands. This reduction is the size of the blind spot represents a very small improvement in vision.
The researchers suggest that this improvement would be so small that people would not even notice it, partly because most people don t even notice their blind spot anyways. However, the results might open up new ways of treating certain types of visual problems. As you have learned, the blind spot is an area on your retina that has no visual receptors. Because of this, there is a tiny gap in your visual field. While your brain usually fills in the missing information so that you don t notice it, this quick and easy test makes it possible to demonstrate the blind spot. Open this image in another browser window. Start by covering your left eye and looking at the star shape with your right eye. Slowly move forward closer and closer toward your computer screen, all the while looking at the star. At some point, you will notice that the circular dot on the right will disappear. That is because it is in your blind spot! If you move even closer to the screen, the dot will suddenly reappear once it moves out of the blind spot on your retina. You can also do the same thing with your other eye. This time, cover your right eye and look at the circular dot with your left eye. Move closer to your monitor until the star suddenly disappears. Be sure to check out our Pof. Learn how they work and what they reveal about the brain. Miller, P. A. , Wallis, G. , Bex, P. J. , Arnold, D. H. (2015).
Reducing the size of the human physiological blind spot through training. Current Biology, 25(17): R747 DOI: 10. 1016/j. cub. 2015. 07. 026. Our eyes have a blind spot for a very good reason. On the back of our eye, the retina is the stuff that detects the light. All the information that the retina picks up is sent to the brain through the optic nerve. The only problem is that the optic nerve needs a way to get out of the eye. The place where it leaves is where we have our blind spot. Since we have 2 eyes that can move around, we don't notice the blind spot often. Here's an interesting way to see your blind spot. First, take a piece of paper and draw 2 small dots on it. Cover one of your eyes. Hold the paper so the dots are on the same level (parallel to the ground). Stare at one dot and slowly move the paper towards and away from you. You will see that the other dot will disappear. That is the dot in on your blind spot and your other eye cannot see it. p. s. You may wonder why the nerves go into the eye and then need a hole to come back out as a bundle in the optic nerve. Why not just head straight back out, and bundle up behind the eye, with no hole? For that, theres no good reason. Its an accident of evolution, where things happened to go wrong and then couldnt get fixed in small evolutionary steps. Squids and octopuses happened to get it right, and have no blind spots. Mike W. (published on 10/22/2007)
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