Emmetropia

Emmetropia (from ancient Greek ἔμμετρος émmetros “to measure”, “suitable” and ὤψ ōps “eye”) is the ophthalmological term for normal vision. An eye is referred to as normally sighted or emmetropic if it sharpens an object that is optically infinitely distant without the need for accommodation . In terms of geometric optics, this means that parallel incident light rays (light source at a great distance) intersect at exactly one point on the retina .

A deviation from this is called ametropia - this includes nearsightedness (myopia), farsightedness (hyperopia) and astigmatism .

The concept of emmetropia is an idealization useful for both theoretical understanding and practical correction of ametropia. In contradiction to the word “normal vision”, the average human eye is in the ametropic range.

A “normal-sighted eye” is generally not a prerequisite for working on optical instruments, because there is usually a diopter compensation on the eyepiece . What is more important here, however, is the freedom from astigmatism (different refractive power of the eye vertically and horizontally). Emmetropia is also not a legal requirement for professions such as B. the airliner pilot , who is allowed an ametropia of up to 3 dpt, the bus driver or skipper. Here, however, high demands are made on visual acuity .

literature

• Theodor Axenfeld (founder), Hans Pau (ed.): Textbook of ophthalmology. 13th, completely revised edition. Gustav Fischer, Stuttgart et al. 1992, ISBN 3-437-00504-9 , p. 13.
• Paul Suter: Introduction to geometrical optics (= Technische Rundschau. The blue TR series. Vol. 35, ISSN  0523-7440 ). 2nd Edition. Hallwag, Bern et al. 1970.
• Herbert Schober: Seeing. Volume 1. 2., improved and expanded edition. VEB Fachbuchverlag, Leipzig 1957.

Individual evidence

1. ^ Wilhelm Gemoll : Greek-German school and hand dictionary. 9th edition, reviewed and expanded by Karl Vretska . Freytag et al., Munich et al. 1965.