Very-High-Frequency Ultrasound Corneal Imaging as a New Tool for Early Diagnosis of Ocular Surface Toxicity in Rabbits Treated with a Preserved Glaucoma Drug

Abstract

Aim: To evaluate very-high-frequency (VHF) ultrasound imaging as a new method to detect and quantify early corneal epithelium changes induced by chronic exposure to a benzalkonium-chloride-containing antiglaucoma drug. Methods: Timolol preserved with 0.01% benzalkonium chloride solution was applied b.i.d. in 1 eye of 10 rabbits for 56 days. Unpreserved timolol solution was used as control. Ocular surface changes were assessed weekly combining clinical examinations, in vivo 60-MHz ultrasound imaging and ex vivo histological analysis. Results: VHF ultrasound imaging allowed quantitative measurement of corneal epithelium thickness and qualitative imaging of toxic epithelial damage. It revealed significantly decreased epithelial thickness in vivo as early as the 21st day of treatment (40.75 ± 1.72 µm at D0 vs. 39 ± 2 at D21, vs. 31.9 ± 2.98 at D56; p = 0.017 and p = 0.005, respectively). The first clinical changes appeared from the 42nd day of treatment (conjunctival redness, conjunctival staining and corneal staining; D56 compared to D0: p = 0.005, 0.01 and 0.004, respectively) and then correlated with VHF ultrasound data. Epithelial thickness measured with VHF ultrasound was correlated with histological epithelial pachymetry (p < 0.001) and with the corneal damage score assessed with scanning electron microscopy (p = 0.038). Conclusion: VHF ultrasound imaging provided an early in vivo diagnosis of corneal epithelium pathology induced by chronic exposure to a preserved glaucoma drug, before the first clinical evidence of ocular toxicity. It could be a new reproducible method to detect the toxicity of glaucoma medication so that therapy can then be adapted.

Short-Term Corneal Response to Cross-Linking in Rabbit Eyes Assessed by In Vivo Confocal Laser Scanning Microscopy and Histology

“…The central corneal thickness of 354 mm measured by CLSM agrees well with measurements obtained by very highfrequency ultrasound 20 and optical coherence tomography. 21 Although significant thickening was observed 3 days after cross-linking, corneal thickness had returned to normal values 1 week after treatment.…”

A novel in vivo corneal trans-epithelial electrical resistance measurement device

“…These experimental systems provide an excellent means for the objective comparison of the potential for cornea injury among several ophthalmic solutions; however, the extent to which these experimental models reflect the condition of the eyes in vivo remains unclear (Denoyer et al, 2008).…”

Less Invasive Corneal Transepithelial Electrical Resistance Measurement Method

“…7,16,17 These experimental systems provide an excellent means of objectively comparing the potential for corneal injury among several ophthalmic solutions; however, the extent to which these experimental models reflect the condition of the eyes in vivo remains unclear. 18 Only a few in vivo studies of corneal electrical properties have been reported, [19][20][21] due to the difficulty of performing such analyses. Recent approaches to performing in vivo measurements have adapted the existing TER measurement methods for use in living animals.…”