Pre-refraction procedures

Pre-refraction procedures

Pre-refraction procedures, such as the measurement of vision or visual acuity and cover testing, are usually performed before the optimum refractive correction is determined. When patients habitually wear spectacles these procedures are conducted with the patient wearing those spectacles, if they have brought them to the examination. Where a patient does not have spectacles these procedures are conducted without any refractive correction in place. When patients wear spectacles for some visual tasks but not others some procedures may need to be done with spectacles and others without.

Pre-refraction procedures
  • PRE014-Interpupillary-distance.pdf

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  • PRE014 Measurement of interpupillary distance

    Interpupillary distance is the distance measured in millimetres between the centres of the pupils of the eyes. This measurement is different from person to person and also depends on whether the patient is looking at distance or near. Consideration of interpupillary distance helps ensure that len...

  • PRE015 Trial frame set up

    The trial frame has to be adjusted for an appropriate vertex distance, inter-pupillary distance and it ensure it sits straight on the nose and comfortably behind the ears. The patient must be looking through the centre of the lens.

  • PRE015-Trial-frame-set-up.pdf

    60.7 KB