Posters

Can we measure corneal epithelial permeability non-invasively in real time? A new corneal bioimpedance testing method can have the answer

Poster Details

First Author: M.Maldonado SPAIN

Co Author(s):    M. Plata-Cordero   A. Guimerà   I. Fernández   R. Villa     

Abstract Details

Purpose:

To evaluate the diagnostic ability and repeatability of a new non invasive micro-nano device to assess corneal epithelial permeability changes through bioimpedance measurements in vivo without transcorneal placement of electrodes.

Setting:

IOBA Eye Institute, Universidad de Valladolid, Spain, and Institut de Microelectrònica de Barcelona IMB-CNM (CSIC), Barcelona, Spain.

Methods:

Fifteen New Zealand White rabbits were used in this study. One eye of each animal was assigned randomly to topical instillation of 0.05% benzalkonium chloride (BAC) or saline solution (SS). Case and control eyes received one drop of each solution, respectively, every minute for 5 minutes, thus completing 5 instillations. A newly developed four-electrode system attached to a Goldmann tonometer, in direct contact with the external corneal surface, was used to register bioimpedance measurements right before and 10 minutes after the application of the first drop. The coefficient of variation (CV) was calculated in order to evaluate the consistency of repeated measurements. To assess epithelial alteration in vivo, we stained the cornea with fluorescein. Also, corneas were processed for optical microscopy with conventional haematoxylin-eosin staining.

Results:

At a frequency of 101 Hz, mean resistance after the instillation of SS (15460.49 ± 5323.39 Ohms) did not differ from basal readings in Control eyes. However, at the same frequency, a significantly lower resistance was measured after BAC application in Case eyes (3768.50 ± 692.22 Ohms; p = 0.004). A distinct fluorescein staining around the central cornea proved the epithelial alteration caused by BAC in the latter group. Optical microscopy samples confirmed these results, showing a partially discohesive epithelium with focal cell swelling, affecting predominantly the basal layer. Conversely, Control eyes did not show any of the findings mentioned above. The best CVs calculated were 14.51 % for the Case Group and 14.61 % for the Control Group, showing in general terms a good to moderate repeatability.

Conclusions:

The resistance readings provided by this new corneal bioimpedance measurement method (CORBI) revealed that variations in the epithelium permeability, thus its barrier function, can be detected non-invasively and repeatedly. Because measurements can be obtained in real time, this novel technology may be most useful to assess corneal epithelial permeability in many clinical and surgical settings including transepithelial corneal cross-linking. FINANCIAL INTEREST: One of more of the authors... gains financially from product or procedure presented