Farsightedness

Farsightedness (hypermetropia). The far point is at a finite distance behind the eye. Parallel rays entering the eye are refracted to the focus, which is behind the eyeball (pic.). This is because:
 * the eyeball is too short (a more common defect, created during embryonic development);
 * the eye has less refraction of the optical system than a healthy eye.

In farsightedness, presbyopia manifests itself much earlier. With decreasing accodommodative ability, hypermetropia eventually needs distance glasses. A special case of hypermetropia is aphakia, which is a defect caused by removing the lens, for example for a cataract.

The defect is corrected with a convex lens.

Related articles

 * Nearsightedness (myopia)
 * Refractive defects
 * Biochemistry of the vision process
 * Eye (Biophysics)
 * Eye (biophysics)/Disorders of the eye
 * Oculomotor muscles
 * Eye (histology)