Eyeballs Change Shape in Animal Experiments : Brain Abnormality May Cause Nearsightedness

Nearsightedness may be caused by brain abnormalities that distort visual information and cause the eyeball to change shape during childhood, researchers said Wednesday.

Studies conducted at Harvard Medical School and Rockefeller University found that young monkeys became nearsighted after having their eyes altered so they could only see vague shapes.

Further research indicated the change was caused by the brain, which received the visual data and sent back information to the eye to induce it to grow longer from front to back.

First Animal Model

The change is believed similar to human development of nearsightedness and offers the first animal model that researchers can use to study nearsightedness, which occurs in 25% of all Americans.

The research was published in the New England Journal of Medicine.

“This finding suggests a new and interesting perspective on the cause of human myopia,” the researchers said. “Perhaps a genetic neural defect exists in subjects predisposed to myopia, so that the normal visual input is perceived as being distorted, and the nervous system responds to the abnormal sensation by causing excessive eye elongation.”

The studies were conducted by sewing shut the eyelids of monkeys for one year. In each monkey, one eye was sewn shut and the other was left open. The closed eye allowed monkeys to see light and shadows but no definite shapes. After a year, the eyes were opened, and it was found the closed eye had become nearsighted while the other had not.