Final answer:
Myopia, or nearsightedness, occurs when an image is focused in front of the retina due to the elongation of the eyeball or excessive curvature of the cornea. Distant objects appear blurry, which can be corrected using concave lenses.
Step-by-step explanation:
Myopia, commonly known as nearsightedness, is a condition where the image is focused in front of the retina rather than on it. This occurs when the eyeball is too long or the cornea has too much curvature, causing distant objects to appear blurry. People with myopia can see near objects clearly but struggle with objects that are far away. To correct this visual defect, concave lenses are used which help refocus the image onto the retina, allowing for clear distant vision. Conversely, far objects are focused with clarity, whereas close objects tend to blur for those with hyperopia (farsightedness), which is corrected with convex lenses.