Hirschberg test
The Hirschberg test , named after the German ophthalmologist Julius Hirschberg , is a simple and orienting examination method for strabismus diseases , which makes use of the position of the corneal reflex images (here the light reflex on the cornea is meant; not to be confused with the corneal reflex ). It is mainly used in patients whose cooperation is insufficient for other procedures (infants, toddlers) or who have a high degree of amblyopia regardless of the fixation .
The examination is carried out with the help of a small light source ( ophthalmoscope , flashlight, etc.). The examiner shines as precisely as possible between both eyes for the patient at the level of the bridge of the nose. If there is no squint, the position of the light reflections is the same on both eyes. These do not necessarily have to be central, but can also be shifted nasally or temporally. The decisive factor is the equality of the decentering, which is dependent on the so-called angle kappa , the angle between the line of sight and the pupil axis. However , if there is a manifest strabismus , the corneal reflexes of both eyes are not located exactly in the same place, but the reflex of the affected eye is shifted depending on the squint deviation. At the same time, this means that rotational squint angles (cyclodeviations) cannot be recorded with the Hirschberg test.
In principle, the Hirschberg test is a qualifying procedure. With some experience you can also estimate the squint angle. A decentering of the reflex by one millimeter from the pupil center corresponds to a deviation of about 8 °. In order to be able to measure the size of a squint deviation, it is also possible, with the aid of a prism bar, to shift the corneal reflex image of the squinting eye until its position is congruent to that of the other eye. The value of the prism then usually corresponds to the objective squint angle. In general, however, this method of squint angle measurement is rather imprecise with an error range of around 3 °. In addition, a possibly existing angle Kappa must be taken into account.
If the Hirschberg test is used for the quantifying measurement of squint angles, it is also known as the Krimsky test .
See also
literature
- Herbert Kaufmann (Ed.): Strabismus. 3rd, fundamentally revised and expanded edition. Georg Thieme, Stuttgart a. a. 2003, ISBN 3-13-129723-9 .
- Albert J. Augustin, James F. Collins: Ophthalmology. 2nd, completely revised and expanded edition. Springer, Berlin a. a. 2001, ISBN 3-540-65947-1 .
