Investigation of sloughed corneal epithelial cells collected by non-invasive irrigation of the corneal surface.

This paper reports the development of a non-contact corneal irrigation chamber (NC-CIC) which enables non-invasive collection of epithelial cells from the corneal surface of human subjects. Cells were viewed by fluorescence microscopy following vital staining with acridine orange (AO). Staining characteristics revealed two corneal epithelial cell types: cells with (i) green and (ii) orange-red cytoplasmic staining. The green cytoplasmic stain appeared to indicate a more viable cell. Multi-cell aggregates were regularly collected from the corneal epithelial surface. Groups of up to seven epithelial cells were obtained. Quantitative studies of corneal epithelial cell sloughing, using isotonic NaCl (305 mOsm/kg) and isotonic "basic tear solution" (BTS, 305 mOsm/kg) as irrigating solutions, involving hourly irrigations between 8 a.m. and 4 p.m. were conducted. Consistently higher cell counts were obtained with NaCl. Using BTS, data scatter was reduced sufficiently to reveal significant differences in sloughing rate as a function of time of day. Instillation of one drop of 0.5% proparacaine caused a significant, but gradual, increase in epithelial cell sloughing rate over a period of hours, as indicated by subsequent BTS irrigations of the cornea. Since the NC-CIC technique is able to discriminate these effects, it may be an appropriate system for in vivo studies of the relationship between corneal epithelial cell mitosis and sloughing.