Corneal innervation and morphology in primary Sjögren's syndrome

To analyze the in vivo morphology of the different corneal sublayers and corneal nerves in primary Sjögren's syndrome (SS).

Ten eyes of 10 patients with primary SS and 10 eyes of 10 sex- and age-matched control subjects were investigated. Diagnosis was based on American-European consensus criteria. In vivo confocal microscopy with through-focusing was used to investigate corneal morphology and to measure corneal sublayer thickness.

Epithelial punctate staining with fluorescein was observed in 6 of 10 SS and none of 10 control corneas. In addition, Schirmer I test results were significantly lower in SS. Epithelial thickness did not differ between the SS and control groups. Confocal microscopy revealed patchy alterations or irregularities in surface epithelial cells in 6 of 10 SS corneas, whereas the basal epithelium appeared normal in all corneas. Average corneal thickness was lower in the SS group (515.9 +/- 22.0 micro m) than in the control (547.4 +/- 42.0 micro m; P = 0.050, t-test). Accordingly, the mean intraocular pressure was lower in the SS group (13.9 +/- 2.1 mm Hg) than in the control (16.7 +/- 2.9 mm Hg; P = 0.022). The subbasal nerve plexus and stromal nerve fiber bundles were present in all corneas. No difference was noted in nerve density. However, in 4 of 10 SS eyes, the subbasal nerve plexus showed structures resembling nerve sprouting, suggesting ongoing active neural growth. None of the control corneas exhibited such features. Signs of anterior keratocyte activation were observed in 5 of 10 SS corneas.

In SS, the corneal surface epithelium was irregular and patchy. Anterior keratocytes frequently showed morphologic features of activation. The subbasal nerve fiber bundles revealed abnormal morphology, and the central corneal thickness was reduced by stromal thinning. The findings confirm epithelial, stromal, and neural abnormalities in the corneas of patients with SS.