The Minds Eye

In The Mind's Eye, Oliver Sacks explores some "interesting" cases of vision. Some people have lost the ability to read, while still having the ability to recognize letters and even write. In other cases, people don't have stereoscopic vision and can't make out the richness of the three dimensions. (And sometimes, like those who are color-blind, they may not recognize what they are missing.) Near the end of the book, the author details his own experience losing visual ability. He had cancer in his eye that caused him to lose all but peripheral vision in an eye, before losing everything. Finally, the book ends with "internal vision". Some blind people "see" and think in vivid images, while others that see do not have the "mind" images. Vision loss can also be different for various people. Vision as a whole is not a simple "on or off", but has many different aspects of physical and neurological ability. Since people only tend to know the way that they experience the world, it can be difficult to generalize a common experience.