The Blind Spot

If we examine the visual field of each eye separately, we find a blind spot about 16° to the temporal (lateral) side of the fixation point. Use Figure 1 to find the blind spot in the visual field of your right eye. The blind spot does not appear as a dark spot. It is simply a region from which we cannot obtain visual information. Print or display the figure so that it is about 12 cm (5 inches) across. To locate your blind spot, look at the figure from about 10 to 12 cm (4 to 5 inches) away. Close your left eye and focus your right eye on the X. In (a), the middle dot on the right should disappear. In (b), when you place the gap at your blind spot, you will see a solid line rather than a broken line. (You may need to adjust the figure closer or farther away to locate your blind spot.) If you keep your left eye closed and look at a uniform area or most patterns with your right eye, you will not be aware of any gap in your visual field. An isolated stimulus, such as the dot in the figure may disappear in the blind spot. King Charles I of England is said to have amused himself by “beheading” some courtiers in this way, before he was literally beheaded himself.

Figure 1  Locating the Blind Spot