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Jiaoyue Hu, Wensheng Chen, Zhiyuan Li, Zhenhao Zhang, Zuguo Liu; The Corneal Morphological Changes by in vivo Confocal Microscopy Reveal Early Toxic Signs Induced by Benzalkonium Chloride. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4210.
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Benzalkonium Chloride (BAC) is the most commonly used preservative in ophthalmic solutions. The topical drugs containing preservatives have long been recognized as a potential risk of ocular surface impair. Recently, a BAC-induced rat dry eye model has been reported. This study was to assess the early toxic effects of BAC on the whole cornea observed by in vivo confocal microscopy (IVCM).
Twelve adult New Zealand rabbits were used in this study. They were randomly selected into four groups treated with three different concentration of BAC (0.01%, 0.05%, and 0.1%) or PBS. The right eye of each rabbit was topically applied with BAC or PBS four times per day. The left eye was used as untreated control. The ocular surface changes were investigated using slit-lamp examination, IVCM and scanning electron microscopy (ECM).
The early toxic effects of BAC on ocular surface were evaluated after 3 days of the treatment. We did not observed the distinct changes of ocular surface impair by slit-lamp examination, including tear film break-up time, Schimer’s test and fluorescein staining in all 4 groups. However, IVCM revealed certain morphological changes in corneas treated with 0.05 or 0.1% BAC: 1) the increased thickness of the whole cornea and the corneal epithelial layer; 2) the increased highly reflective irregular cells in superficial layer with the smaller size cells in basal layer of the corneal epithelium; 3) the presence of highly reflective small round cells and abnormal filamentous structures in the stroma; 4) the appearance of low reflective dark round bodies with enlarged cell size in the endothelium. Furthermore, the cell-cell boundary structures appear loose in the both epithelium and endothelium, which have been confirmed by ECM examination.
Our study reveals the interesting findings that benzalkonium chloride could cause certain corneal morphological changes, the early toxic characteristics, before clinical symptoms appear. The in vivo confocal microscopy is usefully clinical tool in diagnosis of the early stage of the BAC-induced ocular surface impair.
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