Anna Brouwer

Results Table 1 shows the results of the ERG responses of the different DTL positions. Median amplitudes were significantly higher (between 1.12 and 1.19 for the different stimulus strengths, see Table 2) and amplitude ranges were wider for all responses recorded with LLP compared to the FP. In contrast, there were no significant differences in implicit times between the two DTL positions. Figure 2 shows a representative example of ERGs curves of both DTL positions obtained from the same patient. To highlight what the effects may be of an unnoticed shift in DTL position on ERG results, we compared the results of the LLP and the FP to our reference values (obtained with the DTL in the LLP). Here, amplitudes were much more frequently Lower lid Fornix median [IQR] median [IQR] p-value A-wave amplitude* 0.3 -11.8 [-15.5, -8.1] -10.1 [-13.0, -7.4] <0.001*** 1.0 -19.4 [-25.1, -14.3] -16.3 [-20.1, -11.9] <0.001*** 3.0 -29.7 [-37.8, -22.2] -24.9 [-30.5, -19.8] <0.001*** 10.0 -46.1 [-57.2, -35.4] -37.4 [-45.9, -31.4] <0.001*** A-wave implicit time* 0.3 19.0 [18.2, 20.0] 18.9 [18.0, 20.1] 0.445 1.0 17.1 [16.4, 18.0] 17.1 [16.3, 17.8] 0.115 3.0 15.7 [15.1, 16.4] 15.8 [15.1, 16.5] 0.816 10.0 14.8 [14.3, 15.5] 14.8 [14.2, 15.5] 0.119 B-wave amplitude* 0.3 33.3 [23.3, 42.0] 26.2 [20.4, 34.6] <0.001*** 1.0 76.0 [55.5, 97.6] 63.1 [49.9, 82.4] <0.001*** 3.0 119.8 [92.2, 151.7] 103.2 [81.7, 129.1] <0.001*** 10.0 118.4 [93.0, 144.6] 105.0 [82.6, 122.8] <0.001*** B-wave implicit time* 0.3 27.0 [25.8, 30.0] 27.2 [25.6, 29.9] 0.718 1.0 28.9 [27.8, 31.0] 28.8 [27.7, 30.8] 0.105 3.0 31.6 [30.7, 33.0] 31.6 [30.7, 33.0] 0.129 10.0 35.9 [34.8, 37.3] 36.0 [34.7, 37.2] 0.055 30 Hz flicker Peak Amplitude 67.1 [47.2, 86.3] 58.0 [43.9, 74.7] <0.001*** Implicit time 29.1 [27.5, 31.3] 29.1 [27.6, 31.3] 0.461 Descriptive statistics of the ERG responses of the two DTL positions (LLP and FP). * Results of different flash strengths in candela . seconds/meters squared of the light adapted ERG.*** statistically significant Abbreviations: ERG = electroretinogram, DTL = Dawson, Trick, Litzkov electrode, IQR = inter quartile range, LLP = lower lid position, FP = fornix position. Table 1. ERG results and differences of two DTL electrode positions 144 Chapter 7