Effects of benzalkonium chloride on the ocular surface of the rabbit

To evaluate the effects of benzalkonium chloride (BAK) on the ocular surface in rabbits. Eighteen white rabbits were divided into three groups. Topical administration of eye drops was performed four times a day for 14 days; 0.01% BAK for group I, 0.1% BAK for group II, and phosphate-buffered saline (PBS) for the control group. Schirmer test and Rose Bengal staining were carried out and conjunctival impression cytology was performed in both the upper and lower bulbar conjunctiva on days 0, 7, and 14. After day 14, both the upper and lower conjunctiva were evaluated by light and electron microscopy. Immunofluorescence staining was also performed for the detection of mucin 5AC. A decrease in the goblet cell density (GCD) and histopathological changes were more prominent in the BAK-treated groups compared to the control group (P < 0.05). Moreover, these changes were more noticeable in group II than in group I (P < 0.05). The decrease in the GCD and histopathological changes were statistically more significant in the lower conjunctiva than in the upper conjunctiva in the BAK-treated groups (P < 0.05). BAK caused damage to the ocular surface in a gravity-dependent manner. The adverse effects of BAK were more severe in the lower conjunctiva than in the upper conjunctiva.