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A. Schatz, H. Enderle, G. Willmann, A. Messias, K. U. Bartz-Schmidt, E. Zrenner, F. Gekeler; A New Simple Dtl-Electrode for Erg Recording in Animals. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1077.
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© ARVO (1962-2015); The Authors (2016-present)
Contact lens electrodes (CLE) are frequently used to register electroretinograms (ERGs) in small animals (i.e. rats and mice). CLEs are difficult to produce, at times elicit inconstant results, show a high potential to injure the cornea and often contain expensive gold wire to contact the cornea. A new electrode (NDTL) was therefore constructed and tested based on the commonly used DTL-electrode. It consists of a small PMMA tube and a DTL wire, which is easily exchangeable. The NDTL was compared to the CLEs under a variety of ERG settings.
Nine healthy Brown-Norway rats (weight mean 145.2g ± 6,26g) were studied on 2 ERG measurements within 4 weeks. Scotopic ERGs were recorded in the left and right eyes after dark adaptation for at least 12h. For low intensity responses of ERG a Naka-Rushton function was fitted and the parameters Vmax, k and n were analyzed. Further the a-wave, b-wave and OP values (amplitude and implicit time) of brighter flash intensities (3-30 scot cd*s/m2) were compared for CL and NDTL electrodes.
The NDTL shows a lower standard deviation (Mean Vmax 691,83µV ± SD 114,52µV) compared to the CLE (Mean Vmax 657,93 ± SD 120,27µV). Slightly higher amplitudes were recorded in most of the measurements with the CLE (b-wave 3 cd.s/m2 NDTL=834,28µV CLE=815,68µV). A Bland-Altman test shows agreement between the NDTL and the CLE with a mean deviation of difference (CLE-NDTL) of -33,9µV and a range of (±95% CI) 125,75µV. An exploration of the ERG curves demonstrates comparable results for both electrodes. Overall the application of the NDTL was easier (faster adjustment of impedance <10kΩ) and caused less corneal haze after the measurement than the CLE, allowing for subsequent fundus Photography SLO and OCT measurements.
The NDTL produces comparable or better electrophysiological results than the CLE. Most of the disadvantages of the CLE can be prevented by the use of the NDTL. The minimal production costs and the possibility to adapt the NDTL to bigger eyes, such as in dogs or in rabbits and to allow for multiple imaging tests in addition to ERG recording, make a wide application imaginable.
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