Changes in murine subbasal corneal nerves after scopolamine-induced dry eye stress exposure

PURPOSE. To evaluate the morphologic changes in the corneal subbasal nerve (CSN) plexus in wild-type (WT) mice after exposure to scopolamine-induced dry eye stress (DES) by using in vivo confocal microscopy.METHODS. Twenty right eyes of twenty (n = 20) 8-week-old WT BALB/c male mice were investigated. The mice were divided into two experimental groups; 10 eyes of 10 mice exposed to DES for 28 days and 10 eyes of 10 mice were used as a control group. All mice underwent examinations for aqueous tear secretion quantity, tear film breakup time (TBUT), corneal vital staining. and corneal sensitivity thrice (pre-experiment, 2nd week, and 4th week). CSN density, tortuosity, reflectivity, and dendritic cell (DC) densities were examined. RESULTS. The mean aqueous tear secretion (P < 0.0001) and TBUTs (P < 0.0001) were significantly decreased after DES. The mean corneal vital staining scores were significantly higher (fluorescein, P < 0.0001; lissamine, P < 0.0001), the mean TBUTs were significantly shorter (P < 0.0001), and the corneal sensitivities (P < 0.0001) were significantly lower in the dry eye-induced mice than the control mice. The mean CSN fiber density (P < 0.0001) and the reflectivity (P < 0.001) were significantly lower; the mean tortuosity and the mean DC density were significantly higher (P < 0.0001) in the dry eye mice. CONCLUSIONS. Our data demonstrated that prolonged exposure to DES resulted in alterations of CSN density; DC intensity, reflectivity, and tortuosity as well as in tear volume; TBUT; fluorescein and lissamine green staining scores; and the corneal sensitivity in WT mice.