Hypermetropia is a kind of ametropia when parallel beams from distant objects merge behind the retina. A mild form far-sightedness (up to three dioptres) is a normal refraction. Moderate (3,5-6 dioptres) and severe forms (in excess of six dioptres) are believed to be a result of the arrested growth of the eyeball whose cause is not all that clear so far. Vision is usually impaired only in case of moderate or severe farsightedness. Positive lenses usually improve. The hypermetropia degree of adults does not change. However, vision at close distances may deteriorate with age as a result of impaired accommodation.