Laser scanning confocal microscopy for conjunctival epithelium imaging.

BACKGROUND

Conjunctival disorders may adversely affect tear film and promote/induce the development of sicca syndrome (also known as Sjögren's syndrome). The basic diagnostics of sicca syndrome are slit lamp examination and functional tests (such as the Schirmer test, break-up time, or fluorescein/rose bengal staining). However, morphological analysis requires time and effort, both in terms of technical equipment and labor, and the results are not available immediately. In contrast, when using laser scanning confocal microscopy (LSCM), the anatomy and morphology of the conjunctival epithelium may be evaluated in vivo during the clinical examination.

MATERIAL AND METHODS

We examined the conjunctival epithelium of 23 subjects with healthy eyes using LSCM. We compared intraindividual morphological patterns of normal conjunctival epithelium derived from the Heidelberg Retina Tomograph II - Rostock Cornea Module (HRTII-RCM) with those from impression cytology. All examinations were performed on the conjunctiva bulbi at the 12 o'clock position, 2 mm from the limbus corneae.

RESULTS

LSCM and impression cytology examine the conjunctival epithelium from identical perspectives. This facilitates an intraindividual comparison of morphological patterns. In addition, artifact detection and the mapping of light/dark pattern recognition of the LSCM to the microscopy of the impression cytology were reliable. LSCM allows in vivo discrimination of non-secretory from secretory cells in conjunctival epithelium. Non-secretory epithelium shows dark, light and bright cytoplasm of epithelial cells on LSCM, in contrast to impression cytology. Nucleoplasmic ratio ranged from 1:1 to 1:4. Shape, size and interior structure were reliable criteria to distinguish goblet cells from non-secretory cells. The interior structure of the goblet cells showed dark or highly reflective bright homogeneous textures.

CONCLUSION

LSCM is a feasible method for examining the morphology of conjunctival epithelium using non-invasive in vivo imaging. Morphological criteria for squamous metaplasia of the conjunctiva in sicca syndrome are already known from cytology, and can be used in almost the same manner in LSCM. The separation of epithelial microcysts from small goblet cells is difficult with LSCM. Finally, the clinical application of LSCM in the staging of sicca syndrome has to be evaluated in future studies.