[A new quantitative test for parasympathetic nervous function by means of tear volume measurement--application of...

Because reflex secretion of tears is under the sole control of parasympathetic nervous system, tear volume measurement may be useful as a quantitative test for the parasympathetic nervous function. Recently, an electronic resistance measuring device (Peritron: Harco Electronics) has been applied to determine tear volumes. The present study was designed to known whether, or not, the tear volume measured by this device could be an index for the parasympathetic nervous function. By means of Periotron, tear volumes were determined before and after intravenous administration of atropine (500 micrograms) in six control subjects without autonomic and ophthalmologic disorders. Tear volumes were also measured in five patients with acute or subacute hemispheric cerebrovascular disease, in which the parasympathetic nervous function was known to be decreased. In the control subjects, reflex tear volume was 58.6 +/- 13.8 (mean +/- SD) units before the administration of atropine, and it was significantly reduced to 34.1 +/- 9.9 units by atropine (p less than 0.001). In the stroke patients, it was 48.8 +/- 16.5 units in the healthy side and 33.0 +/- 6.7 units in the hemiplegic side, and the value was significantly lower in the hemiplegic side than in the healthy side and in the controls (p less than 0.05, p less than 0.002, respectively). It was concluded that tear volume measurement by means of Periotron was applicable to quantitative assessment of the parasympathetic nervous function.