Study of the corneal epithelial and endothelial permeability in a contact lens human model using a new non-invasive bioimpedance method

Abstract

 

Purpose

 

To assess the safety and efficacy of a new non-invasive bioimpedance prototype for the first time in human corneas under in vivo conditions

 

Methods

 

Ten right eyes from ten healthy volunteers were included in this pilot study. No contact lens (CL) use was allowed seven days before the beginning of the study. A low-Dk CL (Dk=28) or a high-Dk CL (Dk=110) was randomly fitted in the right eye of each subject. Epithelial and endothelial permeability were monitored throughout the study: prior to CL wear (visit 1) and after three days (visit 2) and one week (visit 3) of extended CL wear; using a bioimpedance analysis system, which consists on the placement of a sensor on the corneal surface to perform the measurements (Figure 1). Evaluation of corneal health was carried out with a slit-lamp biomicroscope. Central corneal thickness (CCT) and epithelial corneal thickness (EPC) were monitored with the 3D OCT-2000

 

Results

 

The examination of the corneal surface occasionally revealed slight, superficial punctuate keratopathy in the low-Dk CL eyes, attributable to the wear of the CL. Subjects did not report discomfort while performing the bioimpedance measurement. Eyes fitted with low-Dk CL showed a statistically significant increase (p=0.002 ANOVA with Bonferroni correction) in corneal swelling over time (between visits 1, 2 and 3). After one week of CL use, statistically significant differences (p=0.014 ANOVA) were found for the epithelial swelling between high-Dk CL eyes and low-Dk CL eyes. High-Dk and low-Dk CL eyes showed no statistical significant differences over the study time (between visits 1, 2 and 3) in the epithelial and endothelial permeability. No statistically significant differences between eyes fitted with high-Dk and low-Dk CL were found for epithelial permeability and endothelial permeability. Results are summarized in Figure 2

 

Conclusions

 

This study provides for the first time a quantitative assessment of the permeability of the epithelial and endothelial layers of the human cornea in vivo based on bioimpedance measurements. The method has been shown to be safe and effective in detecting changes in the corneal permeability after CL wear. The results presented may be refined by improving the repeatability and reliability of the impedance system, and establishing the range for normal values  

 

Corneal bioimpedance measurement

 

 

Results