Question
What preliminary technical steps must be followed before VNG?
Answer
A series of preliminary technical steps must be followed before proceeding to perform a VNG exam. Among these, the fundamental moment is that of positioning the goggles.
It is necessary to note:
- The visibility and regularity of the pupillary contour. The latter can be partially hidden by an eyelid ptosis and/or by the projection of the eyelashes. Furthermore, the patient may tend to keep his eyes half closed, sometimes even just because of an incorrect pitch of the head;
- To the sources of black present in the image of the eye that are competitive with the pupillary area: eyelashes, tear film between eyelids and cornea, inhomogeneity of the dioptric media and periocular shadow areas;
- To the attitude of the head that must not present incorrect rotations in the yaw, pitch and roll axes;
- To the infiltration of light along the contour of the goggles that comes into contact with the face;
- To the comfort with which the goggles are worn.
If one or more of the aforementioned conditions occur, it is advisable to correct them in order to obtain a pupillary contour as precise and stable as possible. Among the technical devices useful for this purpose, we can mention the patching of the eyelids, the application of white mascara on the eyelashes, the modification of the pitch angle of the head, and the variation of the grey scale with which the recorded image of the eye.
Please watch these courses for more information, Vestibular and Balance Assessment in Children with Sensorineural Hearing Loss: An Overview and Recent Advances in the Diagnosis and Treatment of Meniere's Disease.
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