A cataract is a painless, cloudy area in the lens of the eye that blocks the passage of light to the retina, the nerve layer at the back of the eye, usually causing vision problems.

白内障是指眼内晶状体的无痛性浑浊阻碍了光线到达视网膜(眼球后部的神经层)，从而引起视力问题。

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The retinal nerve fiber layer is the one part of the brain where nerve cells are not covered with the fat and protein sheathing called myelin, making this assessment specific for nerve damage as opposed to brain MRI changes, which reflect an array of different types of tissue processes in the brain.

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Using the stem cells, researchers have developed cells called oligodendrocytes, which are precursors to nerve cells and which produce a protective layer around nerve cells known as myelin.

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Ann Kelley has found an even more powerful layer of control in the amygdala, a center for emotions that also has rich nerve connections to the nose.

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