Turning a Blind Eye to Blindness

Ursula Mercz was a 56-year-old German seamstress with a history of headaches and vertigo; when she was admitted to the Graz Hospital for Nervous Diseases in November 1894, she had trouble remembering the names of things, and could see only dim outlines of objects in front of her. After a few months, it was obvious she had lost her sight completely; her pupils were unresponsive to light and she could not track movements with her gaze. Yet she categorically denied to attendants at the hospital that she was blind. According to Gabriel Anton, her neurologist, whenever anyone inquired Ursula “stated calmly and clearly that she saw objects that were presented to her...she also claimed to see objects when nothing was presented.” What on earth was going on?

Mercz had a form of anosognosia, a rare and surreal condition in which a patient with a physical defect, even a very severe one, denies that they have any such impairment. Anosognosia can lead patients who are paralyzed on one side of their body to claim, for instance, not just that they can move their immobilized arm, but that they are moving it—right now, can’t you see me? Silly. The version of anosognosia described by Anton, and which came to be known by his name, manifests itself in patients with cortical blindness (blindness caused by damage to the primary visual cortex) and causes them to engage in elaborate visual confabulations.

Although confusion, disorientation, and cognitive impairments have all been observed in patients with Anton’s syndrome, and offer a partial explanation, it has been shown that these factors are not necessarily required in order for the delusion to set in. A patient with no major defects in their intellectual functioning, and who is otherwise essentially aware of the details of their circumstances, may still deny that they are blind. Because their belief that their vision is are normal is so powerful, Anton’s syndrome patients often attempt to navigate without help, stumble into things, and claim that their visual hallucinations are very real. One blind patient, an elderly woman whose doctors “commented favorably on her insight, comprehension, verbal and social skills, and appropriate use of humor,” nonetheless fervently asserted that she had perfectly good vision. Indeed, she believed she was seeing intruders in her room and colorful insects flying into her food.

No one is sure of the precise neurophysiological roots of these delusions. One explanation is that there is a physical disconnect between the part of the brain that processes visual information and the part of the brain that generates a verbal response to what is seen. If the first area could communicate properly with the second, it would report that it had—well—nothing to report. But it can’t. When no report is forthcoming, some neuroscientists believe, the part of the brain in charge of speech and language may be unable to remain silent. Like someone afraid of long pauses in conversations, it makes something up rather than hold its tongue.

Another theory is based on the notion of a false stream of input. This hypothesis holds that what patients think they’re seeing is coming not from their eyes, but from some other part of their brain: the part that maintains a treasury of visual imagery based on past sights. It’s as if, writes neurologist Kenneth Heilman, a TV monitor were receiving scenes coming from a tape or DVD instead of a live television camera.

Whatever the explanation, it’s striking that people with Anton’s syndrome don’t just seem unaware of their blindness; they also seem indifferent to its effects, even when they are pointed out to them. Of Ursula Mercz, Anton wrote in a wondering tone, “The patient was not even aware that there was a reason to be worried or sad about this defect.” In that sense, these patients may not be so different from the rest of us. After all, who hasn’t had at least one friend who seems blissfully oblivious to what seems a painfully obvious truth in his or her life? What Mercz and others like her give us is a profound metaphor for the kind of protective self-deception we all practice to some degree. When life is deficient, it turns out, the brain—for better or for worse—can sometimes do too good a job at making up for it.

We’ve talked at least once before about how the brain mediates vision in fascinating ways.