Blind spot is a small area of blindness that is present in the field of vision of the normal eye. The field of vision refers to everything that people see straight ahead and to the sides as they look steadily at any object.
Doctors can test the field of vision by seating a person 3 feet (91 centimeters) from a wall covered with black cloth. A small white object is then placed on the cloth directly in front of one eye. The other eye is covered with a patch. The person looks steadily at the object as a white-headed pin passes back and forth. If the right eye is being tested, the pin will disappear about 10 inches (25 centimeters) to the right of the white object. This area marks the blind spot.
The blind spot corresponds to the place at which the optic nerve enters the eyeball. There is no vision in this area because there is no retina (inner layer of the eyeball) there. Changes in size and shape of the blind spots give vital information in diseases such as glaucoma and brain tumor.
