Nasolacrimal stimulation of aqueous tear production

Aqueous tear production decreases after anesthetizing the ocular surface. Loss of the nasolacrimal reflex is a risk factor for neurotrophic keratopathy and keratoconjunctivitis sicca. The purpose of this study was to evaluate the effect of nasal mucosal anesthesia on aqueous tear production.

Eleven healthy human volunteers with a normal ocular surface and Schirmer I tear-test scores > 10 mm participated in this study. Schirmer I values were obtained daily for 3 days to establish a normal baseline. On a separate day, the right nasal mucosa was anesthetized with aerosolized 10% lidocaine (Xylocaine). After a 10-min period to allow the anesthetic to take effect and reflex tearing to subside, the Schirmer I test was repeated. A saline nasal spray was used as a control.

Baseline Schirmer I values for both eyes had a mean of 22.98 +/- 1.05 mm (SEM). There was no difference in Schirmer scores between the two eyes after nasal anesthesia (p > 0.6); however, when these were compared with the baseline Schirmer I values, a significant decrease in tear production was noted (p < 0.001). The mean Schirmer I value after nasal anesthesia was 15.18 +/- 1.38 mm (SEM), a 34% decrease from baseline. The difference between the baseline and the normal saline control values was not significant (p = 0.160). There was a significant difference in Schirmer test scores between the saline control and nasal anesthesia groups (p < 0.02).

In addition to sensory neural stimulation from the ocular surface, sensory stimulation of the nasal mucosa also promotes aqueous tear production. These results may help explain the decreased tear production observed in patients who have nasal mucosal damage, disease, or denervation.