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“Faces of perception” states, “Early visual input to the right brain, which arrives via the left eye, proves vital. . . .” Then, the story presents findings based on people born with left-eye cataracts that were later removed. Unfortunately, the signals from the eyes are mixed almost immediately behind the eyes in the optic chiasma. Nasal fibers representing the temporal view of each eye cross to the other side and continue on. In other words, the right side of the brain gets the left field of both eyes, the left side of the brain gets the right field of both eyes. (Central, or macular, vision is combined.) To miss such a basic point throws off any conclusions. Mark Hertzberg
Lawrence, N.Y.
For adults, this description of the eyes’ visual fields is correct. However, Richard Le Grand of McMaster University in Hamilton, Ontario, says that babies see mainly in their temporal visual fields. Infants with right-eye cataracts thus receive visual input mostly from the left eye’s temporal visual field, which is transmitted to the right hemisphere, and vice versa for infants with left-eye cataracts. Le Grand adds that adults born with left-eye cataracts that deprived them of right-hemisphere visual input as infants experience difficulty in seeing faces as unified entities. Adults born with right-eye cataracts do fine at recognizing facial configurations. –B. Bower