FRENZEL GLASSES

Typical Number in Hospital: 1

Cost Bands: 1

References:

One of the standard tests in the investigation of dizziness or vertigo involves asking the patient to look in different directions while the clinician observes the patient's eyes in order to detect an abnormal eye movement called nystagmus. In the normal clinical environment, only patients with acute vestibular problems will exhibit this particular symptom since their eyes will be held steady by observation of the surroundings. A much more sensitive test is to do this in darkness and there are several methods by which the patient's eye movement can be detected. The best method of achieving this is to use an electronystagmograph, although an infrared viewer, or Frenzel glasses, will also allow a subjective assessment of eye movement.

Frenzel glasses comprise a pair of very thick lenses which serve to completely blur the patient's observed environment while giving the clinician a magnified view of the patient's eyes. Two small bulbs built into the frames illuminate the patient's eyes. The advantages of Frenzel glasses over the electronystagmograph and infrared viewer, are low cost and that a totally dark environment is not required, although subdued lighting in the room enhances the effect.