Effects of eye rubbing on the conjunctiva as a model of ocular inflammation

We assessed the effects of eye rubbing on the histologic characteristics and inflammatory cell infiltrate of the conjunctiva. The upper eyelids of 20 adult rats were rubbed during a five-minute period, and then the animals were killed immediately, or at four, eight, or 24 hours after trauma. One eye of each animal was rubbed; the unrubbed contralateral eye served as a control. Counts of mast cells, degranulated mast cells, and inflammatory cells (neutrophils, eosinophils, lymphocytes, plasma cells, and macrophages) were recorded from conjunctival samples from the upper eyelid. Immediately after eye rubbing the conjunctival epithelium was histologically disrupted and 50% of the mast cells showed evidence of degranulation. At four hours after trauma the increase in the number of neutrophils was more than 2,300%. Neutrophils were in the margins in the conjunctival vessels, had migrated into the substantia propria, and were aligned subjacent to the epithelial basement membrane; large numbers of neutrophils populated the epithelium. The four-hour stage was the most dramatic phase of inflammation that occurred from the eye rubbing. At 24 hours there was a significant increase in the number of macrophages. The numbers of lymphocytes, plasma cells, and eosinophils were not significantly changed throughout the study. Our findings demonstrate that eye rubbing histologically disrupts the epithelium and induces significant alteration in the inflammatory cell infiltrate of the conjunctiva. These changes may influence the course of ocular disease.