Far point (optics)
As far point is called the endpoint of the line of sight , the eye without the accommodation is set. He is with the emmetropic (normal vision) eye at infinity (in practice with 6 m is set), the myopic (short-sighted) eye before and during hyperopic behind it. This means that the far point is a real point for people with normal and near-sightedness and a virtual point for people with far-sightedness.
The opposite, i.e. the near point or minimum visual range , is achieved with maximum accommodation. It is around 7 cm in childhood and becomes more distant with increasing age (see figure). The near point is therefore an individual variable that can vary greatly.
The term clear visual range (also called reference or standard visual range ), which is 250 mm, was introduced as a standardized normal value . This guideline value is used, for example, to calculate magnification of magnifying glasses .
Individual evidence
- ^ Theodor Axenfeld (founder), Hans Pau (ed.): Textbook and atlas of ophthalmology. 12th, completely revised edition. Gustav Fischer, Stuttgart et al. 1980, ISBN 3-437-00255-4 .