Electron microscopic evaluation of the effect of therapeutic silicone hydrogel lenses on the limbal area

To investigate the effects of high-permeability silicone hydrogel contact lenses used for therapeutic purposes on limbal cells, inflammation, and neovascularization.

Bullous keratopathy was induced by injection of 0.05% benzalkonium chloride into the anterior chamber of 20 anesthetized rabbit eyes. Ten-millimeter diameter central epithelial erosions were produced, and silicone hydrogel contact lenses were applied onto 10 corneas. Nasal and temporal tarsorrhaphy was performed to leave the central corneal area open. On the 15th and 30th days, the corneas were extracted and examined under electron and light microscopy.

Electron microscopy showed no prominent stress-induced findings in limbal cells in the contact lens group. Epithelial edema was reduced in this group, but on the 30th day, the epithelial edema was greater than that observed on the 15th day. Evaluation of polymorphonuclear and eosinophilic cell infiltration by light microscopy showed that inflammation was less in corneas without contact lenses and the inflammation grade was the same on the 15th and 30th days. Neovascularization was similar in both groups.

The therapeutic use of silicone hydrogel lenses would probably have no effect or, at most, only a slight adverse morphologic effect on limbal area cells. However, when the effects on edema and inflammation were taken into consideration, a 15-day period of wear may be preferable to a 30-day period.