Phoropter
The phoropter is an optical apparatus with which the so-called subjective refraction of a test person can be determined. This is determined on the basis of objectively measured ametropia and is required to adjust glasses or contact lenses . The patient looks from the back of the device through two round openings, the distance between which can be adjusted according to the individual eye relief. The examiner makes the necessary settings from the front.
The use of a phoropter offers adults and older children a convenient way of offering different glass thicknesses in increments of 0.25 diopters and thus checking whether this changes their visual acuity . All the spherical and cylindrical glass thicknesses required for determining the spectacle lens are available. The setting of the axis position of cylinder glasses corresponds to the so-called TABO scheme from 0 ° to 180 °. The phoropter is operated either manually using rotary knobs that are attached to the front of the device, or computer-controlled using a central control console that is connected to the device. In this case, it is also possible via an interface to send values stored in the computer, for example previous glasses values or the results of an objective refraction measurement, directly to the phoropter, which then sets these values.
With a phoropter it is also possible to use color and polarization filters to investigate binocular vision with regard to heterophoria , simultaneous viewing and fusion . Built-in prisms are available for correction , as well as sieve tests for special orthoptic examinations ( Worth test , Schober test ).
Is a functional precursor to the phoropter the trial frame (Colloquially "Vorsteckbrille" trial frame or tasting frame ) in combination with a lens set, one of the glasses-like construction, which also allows for so long stuck different glasses in an appropriate holder and the patient after the Question the result until the optimal values are found. In general, however, the prevailing view is that its handling is by far not as comfortable and quick as that of a phoropter, which is why the measuring glasses are now usually only used for examining people with physical disabilities, small children and for the purpose of trial wear or for Testing of realistic visual situations is used before a correction is finally prescribed and made.
In Germany, the production and quality of phoropters is regulated by the Precision Mechanics and Optics Standards Committee (NAFuO) in DIN EN ISO 10341: 1999.
See also
Web links
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 .
- ↑ Ophthalmic Instruments - Phoropters (ISO 10341: 1997)
