diopter

meaning

Hardly any other word is used so often by opticians, but hardly anyone knows exactly what the term exactly means.
The dioptre is a unit of measurement that indicates the strength with which a lens refracts light. Thus, the diopter is also a key figure for the degree of ametropia, since the power of the glasses takes over the refraction that the ametropia does not perform correctly itself.

Plus values ​​correspond to farsightedness in the dioptric indication, minus values ​​to myopia. The ametropia, whether the dioptric reading is positive or negative, is higher, the higher the dioptric number. This is due to the fact that the refractive power of the spectacle lens is then stronger.

At the optician, the refractive power of the glasses for the glasses is usually given in quarter diopter steps (0.25 diopter steps) and there are only very rarely smaller graduations.

Adjustment of the diopters

For one Myopic will be from a certain Maximum distance everything blurred and only in the Proximity he can without glasses sharp to see. With the self-determined maximum distance, a cure-sighted person can Diopter number of the corrective lens itself.

Example 1: A nearsighted person sees without tools (Glasses) to at most one meter clear. So to see into the distance he needs a lens with the value "- 1 diopter“.

Example 2: When a myopic up maximum 50 cm sharp can see, he already needs it minus two diopters,

Example 3: A myopic with one maximum visual acuity at 33 centimeters , needs a pair of glasses minus three diopters.

This Self-experiments are natural inaccurate and should be at Adaptation of eyeglass lenses precisely and professionally through one optician be performed.

Exact measurements

The opticians have precise measuring devices for determining diopters.

Farsighted People need Plus lenseswho the incident light rays in a focal point like a magnifying glass bundle up. In contrast to nearsighted people, farsighted people can also have their ametropia not yourself from her personal focus range estimate her.

Instead, the value for a lens with farsightedness calculated. The distance of the lens until Focus is called Focal length. The Diopter number of the plus glass is that Reciprocal of the focal length.

Examples: With a plus lens, the light rays meet in one meter, so the lens has a power of plus 1 diopter. If they meet within 50 centimeters, that is the power plus two diopters. If the focal point is 33 centimeters away, this means a dioptric number of plus 3. From this the rule can be derived: the shorter the focal length, the stronger the plus lens.