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Is everyone's blind spot different?
No, everyone's blind spot is located in the same area of the retina, where the optic nerve connects to the eye. However, the size and shape of the blind spot can vary slightly among individuals.
Does the optic nerve cause a blind spot?
The optic nerve (also known as cranial nerve II) is a continuation of the axons of the ganglion cells in the retina. There are approximately 1.1 million nerve cells in each optic nerve. The optic nerve, which acts like a cable connecting the eye with the brain, actually is more like brain tissue than it is nerve tissue. As the optic nerve leaves the back of the eye, it travels to the optic chiasm, located just below and in front of the pituitary gland (which is why a tumor on the pituitary gland, pressing on the optic chiasm, can cause vision problems). In the optic chiasm, the optic nerve fibers emanating from the nasal half of each retina cross over to the other side; but the nerve fibers originating in the temporal retina do not cross over. From there, the nerve fibers become the optic tract, passing through the thalamus and turning into the optic radiation until they reach the visual cortex in the occipital lobe at the back of the brain. This is where the visual center of the brain is located. The visual cortex ultimately interprets the electrical signals produced by light stimulation of the retina, via the optic nerve, as visual images. A representation of parasympathetic pathways in the pupillary light reflex can be seen here: parasympathetic response. The beginning of the optic nerve in the retina is called the optic nerve head or optic disc. Since there are no photoreceptors (cones and rods) in the optic nerve head, this area of the retina cannot respond to light stimulation. As a result, it is known as the "blind spot," and everybody has one in each eye. The reason we normally do not notice our blind spots is because, when both eyes are open, the blind spot of one eye corresponds to retina that is seeing properly in the other eye. Here is a way for you to see just how absolutely blind your blind spot is. Below, you will observe a dot and a plus. This The End The optic nerve causes a blind spot because it is a continuation of the axons of the ganglion cells in the retina.
Why does the optic nerve cause the blind spot?
The optic nerve (also known as cranial nerve II) is a continuation of the axons of the ganglion cells in the retina. There are approximately 1.1 million nerve cells in each optic nerve. The optic nerve, which acts like a cable connecting the eye with the brain, actually is more like brain tissue than it is nerve tissue. As the optic nerve leaves the back of the eye, it travels to the optic chiasm, located just below and in front of the pituitary gland (which is why a tumor on the pituitary gland, pressing on the optic chiasm, can cause vision problems). In the optic chiasm, the optic nerve fibers emanating from the nasal half of each retina cross over to the other side; but the nerve fibers originating in the temporal retina do not cross over. From there, the nerve fibers become the optic tract, passing through the thalamus and turning into the optic radiation until they reach the visual cortex in the occipital lobe at the back of the brain. This is where the visual center of the brain is located. The visual cortex ultimately interprets the electrical signals produced by light stimulation of the retina, via the optic nerve, as visual images. A representation of parasympathetic pathways in the pupillary light reflex can be seen here: parasympathetic response. The beginning of the optic nerve in the retina is called the optic nerve head or optic disc. Since there are no photoreceptors (cones and rods) in the optic nerve head, this area of the retina cannot respond to light stimulation. As a result, it is known as the "blind spot," and everybody has one in each eye. The reason we normally do not notice our blind spots is because, when both eyes are open, the blind spot of one eye corresponds to retina that is seeing properly in the other eye. Here is a way for you to see just how absolutely blind your blind spot is. Below, you will observe a dot and a plus. This The End The optic nerve causes a blind spot because it is a continuation of the axons of the ganglion cells in the retina.
Where does a blind spot in the retina occur?
Most commonly, blind spots in the retina are on or nearby the pupil/iris. It should be looking "clouded" and they might even get a blue tint to them. -------------------------------------------------- The above answer makes very little sense at all but I'll leave it in for now just in case it is somehow what was wanted. It'd be fairer to let an objective adjudicator decide. Anyhow....a blindspot on the retina occurs at the optic nerve. This is because as light enters the eye (through the pupil) it is projected onto the retina, which is essentially the back wall of the eye. Your retina is covered in tiny little sensors known as rods and cones (generally speaking cones allow colour vision during the day and rods allow the grainy black and white sight in the dark). So when light hits these cells, it breaks down pigments inside the cell according to wavelength (thus colour!) and that sends signal from that cell to the brain. There are millions of these in each eye and when you add them all up, you get a complete picture of that which is projected upon the back of your eye. However! All of these cells must have nerves running from them to the brain so these signals can be sent. All of these nerves from the retina are bundled together, where they meet at a certain point in the retina and then lead out the back of the eye into the brain. This bundle is called the optic nerve and obviously at that point on the retina, there's no rods or cones...meaning no light at that point is actually collected or processed, giving you a blind spot. To demonstrate this, you can do a classic blind spot test. You can do it with paper and a pencil, or there's a web version here: http://www.blindspottest.com/
What causes your blind spot?
At the small spot in each eye where the optic nerve exits the eye, they are no light receptors and therefore no vision. The blind spots are to the outer sides of the field of vision and therefore less critical than if they were close to the center. Also, the blind spot in each eye is compensated for by the other eye for those who have two intact eyes.
Why are cucumbers and lepurcaunes green?
Because they each reflect the portions of light that when striking the retina of our eyes, cause the sensation that we perceive as green in our brain.
How Has the evolution of the eye give an example of evolution in general?
The eye is a good example because there are living animals with eyes that represent each step in it's evolution. Human eyes also show how evolution can produce "bad" results; the retina is essentially "inside-out" - the nerves are on top and there is a blind-spot where the optic nerve leaves the eye.
Functions of blind spot?
The blind spot is an area in the back of the eye where the optic nerve exits, lacking light-detecting cells. It does not contribute to vision but allows blood vessels to enter and exit the eye. The brain compensates for this blind spot by filling in missing visual information, resulting in seamless perception.
How many blind dolphins are there each year?
1000
Where in the retinas are the blind spots located?
The blind spot of each eye is located where the optic nerve leaves the eye.
What is the reason for weak eyesight of their children?
Because of vitamin A deficiency. About 250,000-500,000 malnourished children in the developing world go blind each year from a deficiency of vitamin A and around 50% of those die within a year of becoming blind.
What is a blind level?
A blind level is a level or drainage gallery which has a vertical shaft at each end, and acts as an inverted option.
