Mention one reason for this defect.

The EYEBALL IS TOO SHORT from front to back, so the image of a near object falls behind the retina. (Also acceptable: the lens is too flat, or the ciliary muscles are too weak to make it sufficiently convex, so the eye cannot bend the light enough.)

One reason only, so give one.

Both possible causes amount to the same thing — the eye does not bend light ENOUGH, so the focus falls too far back.

THE SYMMETRY with myopia is worth holding, because it makes both defects derivable rather than memorised: MYOPIA — eyeball too LONG or lens too CONVEX — bends light TOO MUCH — image IN FRONT of the retina HYPERMETROPIA — eyeball too SHORT or lens too FLAT — bends light TOO LITTLE — image BEHIND the retina Each is the exact opposite of the other in every respect.