This denotes the size of the greatest vocal fold displacement from the midline. The mucosal wave is evident during vibrations except during falsetto. Stroboscopy is as useful to the clinician as indirect or direct laryngeal endoscopy, since it allows evaluation of the dynamic aspects of vocal fold vibrations. Stroboscopic examination of the vocal folds provides information for a quick, precise diagnosis useful for both surgical therapy and followup. Many clinical difficulties can be attributed to anomalies of the mucosal wave of the vocal folds.
Stroboscopic examination permits assessment of vocal fold flexibility.
Commonly, the instrument is coupled to video recording systems for research, teaching, treatment, and documentation. Stroboscopy may be performed orally through a telescope or a nasopharyngoscope. The stroboscopic effect is based on an optical illusion caused by persistence of visual images. The eye cannot discriminate separate images that last less than 0.32 seconds because of the interaction between the length of the stimulus image and the persistence of the image on the retina. This explains why, to the unaided eye, the vibrating vocal folds seem to be stationary except for some low frequency movements under certain conditions.