Phoropter
The phoropter is an ophthalmic apparatus with which the so-called subjective refraction of a subject can be determined. This is calculated on the basis of objectively measured refractive errors ( ametropia ) is determined and requires the adaptation of lenses or contact lenses. Advise the patient of the back of the device looks through two circular openings, the distance can be adjusted according to the individual eye relief. The examiner takes the front of the necessary settings.
The use of a phoropter offers a convenient way to offer different glass thicknesses in steps of 0.25 diopters adults and older children and to examine as to whether the visual acuity changed by it. All components necessary for a lens determination spherical and cylindrical glass thicknesses are available to you. The adjustment of the axial position of the cylinder glasses corresponds to the so-called TABO schema from 0 ° to 180 °. The refractor is operated either manually by turning knobs that are attached to the front of the apparatus, or computer- controlled by means of a central control console which is connected to the device. Via an interface, it is also possible in this case, to send in the computer stored values , as previous spectacles values or the results of an objective refraction directly to the phoropter, which then adjusts these values.
In addition, it is possible with a phoropter to perform using color and polarization filters investigations of binocular vision in terms heterophoria, simultaneous vision and fusion. For correction are built prisms available, as well as screening tests for special orthoptic examinations ( Worth test, Schober test).
A functional precursor of the phoropter is the trial frame ( Colloquially, along with tasting glasses or tasting frame ) combined with a glasses box, one of the glasses similar construction, which is also welcome as long to put different lenses in an appropriate holder and inquire of the patient according to the results, are to the optimal values found. There is general, however, the view before, its handling is not nearly as comfortable and fast as a phoropter, which is why the trial frame today usually only for the study of people with disabilities, young children and for the purpose of tentative wearing or testing is used by real-world visual situations before a correction is finally enacted and made .
Production and quality of phoropters regulates in Germany of Optics and Precision Mechanics Standards Committee ( NAFuO ) in the DIN EN ISO 10341:1999.