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M. Fukuda, H. Sasaki, N. Takahashi, M. Yoshikawa, M. Kojima, K. Kitagawa, Y. Sakamoto, K. Sasaki; Development of Technique to Measure Corneal Resistance That Can Be Used to Evaluate Corneal Injury. Invest. Ophthalmol. Vis. Sci. 2008;49(13):608.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate a newly developed device for estimating corneal disorder in vivo by measuring the corneal resistance quantitatively and non-invasively.
A contact lens electrode was used to measure the corneal resistance in albino rabbits. Two concentric silver wire electrodes were attached to the inner surface of a contact lens and served as bipolar electrodes (Mayo Corporation; Aichi, Japan). The electrical current was generated by an electronic pulse generator and delivered through a constant current isolator (BSI-2; BAK Electronics, INC. USA). The parameters of the current were; frequency=0.5 Hz biphasic square wave pulses, duration=5 sec, and current= ± 50 µA. The time course of voltage change was recorded from the electrode set over the cornea and stored in a computer for on and off line analyses (PowerLab; AD Instruments, Australia). The polarity, resistance, and plasticity were measured. We also measured the corneal resistance in the rabbit (Male New Zealand white 2.5~3.0kg) eyes with corneal epithelial defect for 6mm diameter by 1 -Heptanol. In another experiment, 0.02% benzalkonium Chloride (BAK) solution was instilled into the cul-de-sacs of rabbit eye 5 times at 5-minute intervals and the corneal resistance of these eyes with superficial punctate keratitis (SPK) made by BAK was measured. Corneal epithelial change was confirmed by fluorescein staining in slitlamp biomicroscope.
The corneal resistance was 1081±172 Ω (n=5; mean ± SD) in normal rabbits. The corneal resistance was decreased to 555 ±49Ω(n=5; mean ± SD) (63% of control) after detachment of all layers by 1-Heptanol. The corneal resistance in the eyes with topical BAK solution at 1, 5 and 10minutes after final administration were 94%, 80% and 59% of that in the normal eyes. There were extensive SPK at 10 minutes. The corneal resistance recovered to 80% of control eyes at 24hr after instillation when there was no corneal fluorecein staining.
These results indicate that electrodes embedded in a contact lens can be used to measure the resistance of the cornea. This will allow the quantification of changes in resistance in eyes with corneal disorders. This will be a useful device for measuring corneal disorders in vivo.
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