1.

Early in March 1986 one of us received the following letter:

I am a rather successful artist just past 65 years of age. On January 2nd of this year I was driving my car and was hit by a small truck on the passenger side of my vehicle.

When visiting the emergency room of a local hospital, I was told I had a concussion. While taking an eye examination, it was discovered that I was unable to distinguish letters or colors. The letters appeared to be Greek letters. My vision was such that everything appeared to me as viewing a black and white television screen.

Within days, I could distinguish letters and my vision became that of an eagle—I can see a worm wriggling a block away. The sharpness of focus is incredible.

BUT—I AM ABSOLUTELY COLOR BLIND.

I have visited ophthalmologists who know nothing about this colorblind business. I have visited neurologists, to no avail. Under hypnosis I still can’t distinguish colors. I have been involved in all kinds of tests. You name it.

My brown dog is dark grey. Tomato juice is black. Color TV is a hodge-podge. Etc., etc.

This seemed an extraordinary letter. The artist was not born colorblind, which is what one immediately thinks of when people say they are “colorblind.” When one speaks of colorblindness, one usually is speaking of an inborn defect in seeing particular colors. This condition was described in the 1780s by John Dalton, who suffered from it himself, and it is sometimes called “Daltonism.” Probably it has always existed, and indeed been quite common: it is estimated that between 4 and 5 percent of men have the common red-green colorblindness, while it is much rarer in women. Extremely rarely (the estimated incidence is only one in five million), people may be born wholly colorblind. The cone cells of the retina, of which there are three groups, respond differentially to wavelengths, and serve as our primary color receptors. In those born partially or totally colorblind, some or all of one type of light-sensitive cones, occasionally two types, are missing, or missing their light-sensitive pigment.

But clearly none of these conditions applied to our correspondent, Jonathan I. He had seen normally all his life, had been born with a full complement of cones, or color receptors, and presumably still had these. He had become colorblind, after sixty-five years of seeing colors normally. And he did not just confuse some colors or see them as gray, as is usually the case with the congenitally colorblind. He had become totally colorblind—as if “viewing a black and white television screen.” All this came on suddenly when he had an accident. The suddenness of the event was incompatible with any of the slow deteriorations that can befall the retinal cone cells, and suggested, instead, a mishap at a higher level, in those parts of the brain specialized in perceiving color.

Total colorblindness caused by brain damage, so-called…