Purpose: The aim of this study was to compare, in vivo on a rat model, two different preservatives— benzalkonium chloride (BAC) and polyquaternium-1 (PQ-1)—using new experimental
approaches.
Methods: Thirty (30) eyes of 15 male Lewis rats were used in this study. Rats were randomly
divided into five groups instilled twice a day for 11 days with eye drops containing different
concentrations of preservatives, 0.1% BAC, 0.5% BAC, 0.1% PQ-1, 0.5% PQ-1, and balanced
salt solution (BSS) as a control. The ocular surface toxicity of these two preservatives was investigated
using new in vivo experimental approaches. Slit-lamp examination, the fluorescein
test, the red phenol test, impression cytology, and in vivo corneal confocal microscopy
were used to evaluate the rat ocular surface after preservative instillation. Histology sections
and immunohistochemistry were also examined to confirm these results.
Results: Compared to PQ-1, BAC consistently and dramatically altered the corneoconjunctival
surface as evaluated by slit-lamp examination, the fluorescein test, impression cytology,
in vivo confocal microscopy, and histology. The 0.5% BAC solution also significantly decreased
tear production compared to the control. Although 0.5% PQ-1 significantly decreased
goblet cell density in comparison to the control, and some abnormalities were observed with
in vivo confocal microscopy, no statistically significant differences were observed between
these two groups using the tear production test, slit-lamp and fluorescein evaluation, or histology.
Conclusion: Using an acute rat model of ocular toxicity by comparing preservatives at high
concentrations, we demonstrated in vivo that high doses of PQ-1 were much less toxic than
BAC. In vivo confocal microscopy and impression cytology are new promising experimental
approaches to studying the rat corneoconjunctival surface, particularly in the field of ocular
surface toxicity.
