Histological and immunohistochemical study on the effect of polyhexanide-preserved contact lens solution on albino rat cornea and the possible protective role of carboxymethylcellulose

ABSTRACT

The use of contact lenses has been widespread for the correction of vision or even for cosmetic reasons. The common use of solutions containing polyhexanide warranted an investigation into the possible effects of this agent on corneal structure. Carboxymethylcellulose is commonly used in artificial tears. It may have cytoprotective properties on the ocular surface. This study was conducted to evaluate the histological changes that may occur in rat cornea after long-term exposure to a polyhexanide-preserved contact lens solution and the possible protective role of carboxymethylcellulose. Forty adult male albino rats were divided into four equal groups; control group, carboxymethylcellulose-treated group, polyhexanide-preserved solution-treated group and the fourth group was treated with carboxymethylcellulose followed by polyhexanide- preserved solution. The animals were treated topically once daily for eight weeks. Corneal specimens were processed for both light and electron microscopy. Cellular proliferation was further evaluated immunohistochemically using the Proliferating Cell Nuclear Antigen [PCNA]. Specimens of animals treated with polyhexanide-preserved solution showed focal cytoplasmic vacuolation, nuclear pyknosis, swollen mitochondria in the epithelial cells with widening of intercellular spaces. The stroma showed disorganized collagen fibrils, vascularization and cellular infiltration. The endothelial cells showed cytoplasmic vacuolation, swollen mitochondria and were abnormally stratified. Immunohistochemical study revealed a non significant increase in PCNA-positive nuclei in the epithelial cells. In contrast, corneal structure was more preserved in rats treated by pre-application of carboxymethylcellulose followed by the contact lens solution with a highly significant increase in PCNA-positive nuclei. Long-term topical application of polyhexanide-preserved contact lens solution induced structural changes in the cornea that could be partially minimized by pre-application of carboxymethylcellulose