A new DTL-electrode holder for recording of electroretinograms in animals

Contact lens electrodes (CLEs) are frequently used to register electroretinograms (ERGs) in small animals such as mice or rats. CLEs are expensive to buy or difficult to be produced individually. In addition, CLE's have been noticed to elicit inconstant results and they carry potential to injure the cornea. Therefore, a new electrode holder was constructed based on the clinically used DTL-electrode and compared to CLEs.

ERGs were recorded with both electrode types in nine healthy Brown-Norway rats under scotopic conditions. For low intensity responses a Naka-Rushton function was fitted and the parameters V(max), k and n were analyzed. The a-wave, b-wave and oscillatory potentials were analyzed for brighter flash intensities (1-60 scot cds/m²). Repeatability was assessed for both electrode types in consecutive measurements.

The new electrode holder was faster in setting up than the CLE and showed lower standard deviations. No corneal alterations were observed. Slightly higher amplitudes were recorded in most of the measurements with the new electrode holder (except amplitudes induced by 60 cds/m²). A Bland-Altman test showed good agreement between the DTL holder and the CLE (mean difference 35.2 μV (Holder-CLE)). Pearson's correlation coefficient for test-retest-reliability was r=0.783.

The DTL holder was superior in handling and caused far less corneal problems than the CLE and produced comparable or better electrophysiological results. The minimal production costs and the possibility of adapting the DTL holder to bigger eyes, such as for dogs or rabbits, offers with broader application prospects.