The root cause of hyperopia is a structural defect in the eye that causes blurry vision. The eye may be shorter than normal, the cornea may be flatter than normal, or the lens of the eye may not be positioned correctly. In most cases, this does not cause a problem with eyesight until the 40s, when the focusing mechanism in the eye begins to lose the ability to compensate for structural abnormalities. This results in light rays being focused behind the retina of the eye, rather than on it, and consequently vision becomes blurred. While the most common symptom of farsightedness is the inability to see near objects clearly, with some people a small degree of nearsightedness may also result.
Most newborn babies have a small degree of hyperopia, however the lenses of the eye are very flexible at birth, and this fully compensates for farsightedness in very young children. Almost all babies will out-grow this condition as a result of normal childhood development.
Farsightedness is a hereditary condition, meaning it can be passed on from parents to children. More rarely, hyperopia may be caused by diseases of the eye such as tumors or lens dislocation caused by accident or injury.