Some people have nearsightedness (myopia) and farsightedness (hyperopia) because the distance between their and their is either too short

lens; retina

In myopia, close objects look clear but distant objects appear blurred. Hyperopia is the reverse of myopia. Here you can see distant objects clearly, but have difficulty focusing on objects that are near. People have myopia (nearsightedness) and hyperopia )farsightedness) because the distance between their lens and their retina is either too short or too long.

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the sphincter muscles at the end of the digestive tract is the anus.