She's blind, but she sees

Defective gas water heaters can be extremely dangerous. A woman from England called Dee Fletcher had the misfortune to find this out herself in 1988 when she was taking a shower in the new house she and her husband Carlo had bought in a small village north of Milan. Unaware of any possible dangers she decided to freshen up in her new bathroom, carelessly started to shower, never even thinking of the possibility that deadly gasses were filling the air. The room was not well aired, so the flame did not have enough oxygen to burn which lead to the accumulation of the deadly carbon monoxide.

This gas is very dangerous because it has no scent, so one usually does not sense its presence until it is already too late. Unfortunately, this is exactly what happened to Dee. She lost consciousness and would have died soon after if Carlo had not returned home at that very moment. He immediately started to resuscitate her and quickly got her to the nearest hospital where they saved her life. At first, nobody knew how much time her brain had been deprived of oxygen, which could have caused permanent damage. The brain is the organ which suffers the most rapid deterioration when it is not provided oxygen. A few minutes of interrupted oxygen supply are enough to cause brain cells to start dying.

She can’t distinguish objects, but she sees their details

When Dee woke up in the hospital the doctors were quick to realize that the carbon monoxide poisoning did not go by without leaving consequences. Even though she could speak normally and understand what others were saying, she could no longer see. The doctors’ first diagnosis was that the poisoning had destroyed the sight center in the brain, but they had to change their opinion in the next couple of days as Dee started to show signs of sight. When Carlo came to visit her she mentioned that he was wearing the same sweater as the previous day. She also knew that outside the sky was clear, and that the flowers in her room were red and blue.

When her mother arrived from England she did not even recognize her when she first came into her hospital room. It was not until she heard her voice that she was gladdened by her presence. On the other hand, Dee had no difficulties with handling objects and recognizing colors. The next day when she and her mother were having a cup of coffee something even more unusual happened. She was surprised at her own ability: “You know what’s strange, mom? I can see the little hairs on your arms perfectly clearly!”

Her mother was beside herself with joy when she heard her say this, because she thought that her daughter would gradually regain her sight after all, but the happy moment was only short-lived. It became evident that Dee could no longer recognize the shape of the objects she was looking at. Even though she could discern the color and texture of an object, she could not figure out what kind of an object it was. The poisoning had caused Dee to lose only a part of her ability to see. Although she could still see the colors and the structure of the surface of individual objects, she could no longer make out their shape.

Blind to shapes

Her blindness was later studied by English neurologists who discovered that she was still able to distinguish colors very well. She was capable of recognizing very small nuances in the shades of individual colors. She could also tell if an object was made of plastic, wood or metal, but she could still not discern shapes. When she was shown parallel lines on a computer screen she had no trouble with recognizing the pattern she saw, but she could not determine whether the lines were vertical or horizontal.

It is necessary to state that she had no previous problems with her eye-sight which, of course, could have caused her to have blurred vision like someone who is very short-sighted. Her vision was completely clear and sharp which is supported by the fact that she could recognize from a distance the colors and patterns that myopic people could not see. After thorough examination it became clear that Dee was only blind to shapes, but otherwise had perfect vision. It does not matter what the shape in question might be, Dee can not recognize it. However, she does not have a problem with interpreting what she is seeing, but with the process of looking itself. It is not a matter of her brain recognizing shapes, then failing to interpret them and link them to words. Dee simply can not see shapes.

When doctors asked her to draw an apple from memory she did very well, but when they gave her an image of an apple to copy, all she was able to draw were indistinct scribbles. During the first years following the accident she also had nightmares which were quite different than the usual ones. For her, the nightmare began when she woke up. When she dreamed, her sight was fine, but when she woke up she came back into her unusual shapeless world.

The medical term for the condition in which people are no longer capable of recognizing things that surround them, even though their eyes function normally, is called “agnosia”. The term was coined at the end of the nineteenth century by the, at the time still unknown, neurologist Sigmund Freud who used it to describe patients who had difficulties with establishing the meaning of what they saw. Of course, there are many different kinds of agnosia depending on which part of the patient’s brain is damaged. In medical literature, many types of this “conceptual blindness” have been described, some of which are also quite exotic, such as amusia, in case of which the patient has no ability to recognize music, even though his hearing is intact.

Dee’s condition is a case of visual form agnosia. However, it is not a classic example of the disease. Neurologists were surprised to discover that Dee was completely capable of picking up a pencil, though she was not able to recognize its form. Regardless of how the pencil was placed on the table or which direction it faced she could pick it up effortlessly which implied that she did perceive shapes somehow, but was not aware of it. If she were completely blind to shapes she would not be able to pick up the pencil as easily.

Do people have two separate brain mechanisms for seeing?

When researchers delved deeper into Dee’s case, they became increasingly aware of the fact that Dee could still respond to the outside environment very well, as if she had perfectly good eyesight, but at the same time could not understand what kinds of forms she was actually seeing. What did this mean? Researchers made the hypothesis that people do not only have one, universal mechanism that gives meaning to what we see or, in other words, the information that travels from our eyes to our brain via our nerves. Dee’s case of agnosia clearly suggests that in our brains two separate processes of visual information analysis are at work: the first supports the coordination of movement and is independent of the second which creates an inner image of the outside world. In Dee’s case the poisoning accident damaged the second mechanism, while the first continued to function normally.

The theory of two modules for processing visual perception in the brain has been developed by two British neurologists, Melvyn A. Goodale and A. David Milner, and presented in their book Sight Unseen: An Exploration of Conscious and Unconscious Vision (Oxford University Press, 2004). In it they also give a detailed description of the case of Dee Fletcher who they examined and tested on several occasions following her accident. In the book, they also present cases of patients with the inverse combination of symptoms of those Dee has. It can also happen that the patient can recognize shapes, but cannot recognize colors. However, this is not a classic example of color blindness where the color receptors in the eye are damaged. These patients are capable of effortlessly passing the classic color blindness tests, because they can distinguish the borders between two different colors of the same intensity, which the typical monochromats cannot do, but they are still unable to tell which color they are seeing. When asked to draw a banana, for example, nothing would stop them from choosing a red or a green crayon instead of the yellow one.

Fifteen years after the accident the two scientists went to visit Dee and her husband Carlo in their home. They say that when Dee came to open the door, she showed almost no signs of blindness at all. She has no difficulties with moving through her home quickly, cooking and even working on the garden which she was also glad to show them. When they went for a short trip the following day she seemed to follow the forest path easily, and they only had to tell her which the right trail was occasionally.

Although she never regained perfect vision, Dee succeeded in making use of the sight mechanism which remained unharmed after the accident. She now tells people apart by the color of their clothes and the details in the structure of the surface that she can recognize. She uses the same technique when doing household chores which she now performs considerably better than immediately after the accident.