In vivo Very–High–Frequency Ultrasound Imaging and Measurement of Corneal Epithelial Changes Induced by Chronic Exposure to BAC in Rabbit Eyes

Abstract

Abstract: : Purpose: To evaluate very–high–frequency (VHF) ultrasound in the in vivo follow–up of corneal epithelial changes induced by chronic exposure to benzalkonium chloride (BAC). Methods: 0.01% BAC–containing solution was applied twice a day in the tested eye of 10 rabbits during 56 days. We used a 60 MHz ultrasound device to assess ocular surface of BAC–exposed eyes, compared with non–exposed eyes. This comparative prospective study included both clinical and ultrasound examinations every 10 days, and ultimate histological analysis. Results: Clinical changes were conjunctival redness, conjunctival and corneal staining and decreased break–up–time. In vivo VHF ultrasound revealed a decrease in absolute epithelial thickness of tested eyes (from 40.9 ± 1.6 SD µm at D0, to 31.8 ± 3.4 SD µm at D56 ; P = 0.0006 for D0 vs D56), and a decrease in relative epithelial thickness of tested eyes compared with controls (from –0.3 ± 1.9 SD µm at D0 to –9.1 ± 2.9 SD µm at D56 ; P = 0.0003 for D0 vs D56). VHF ultrasound epithelial thickness was correlated with corneal staining (at D34 and D56 ; P = 0.0025 and 0.0377, respectively) and histological epithelial pachymetry (P = 0.0176 for control and 0.0505 for tested epithelium). Moreover, we reported qualitative VHF ultrasound imaging of epithelial damages including superficial punctuate keratitis. Conclusions: VHF ultrasound allowed an in vivo assessment of epithelial changes induced by topical preservatives ; it could be a reproducible and reliable tool for evaluation of ocular surface toxicity.

Keywords: cornea: epithelium • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • ocular irritancy/toxicity testing