Does short sightedness (myopia) or long sightedness (hypermetropia) imply necessarily that the eye has partially lost its ability of accomodation ? If not, what might cause these defects of vision ?

Explanation

No, short-sightedness or long-sightedness does not necessarily imply that the eye has partially lost its ability of accommodation. A myopic or hypermetropic person may have normal ability of accommodation of the eye lens. Myopia arises on elongation of the eye ball. Hypermetropia arises by the shortening of eye ball. When the eye ball has normal length but the eye lens loses its ability of accommodation partially, that defect is known as presbyopia.