Figures (3)  Tables (4)

    • Figure 1. 

      (a) Illustrative graph of VEP signals from the right eye of a healthy male volunteer showing 80 individual trials (gray) along with the averaged signal (bold dark line). (b) The same averaged signal is shown on an enlarged scale with the characteristic components N75, P100, and N135 indicated.

    • Figure 2. 

      Diagram of the electrode placement along the midline of the scalp used in visual evoked potential examination. (Original illustration by the authors).

    • Figure 3. 

      Correlations between age and analyzed parameters.

    • Variable n (%) / M ± SD Me (IQR) Range
      N 108 (100.0) − −
      Sex
      Male 55 (50.9) − −
      Female 53 (49.1) − −
      Age (years) 37.19 ± 15.58 33.00 (24.00; 48.25) 18.00–75.00
      Males (years*) 33.49 ± 13.94 31.00 (23.00; 42.00) 18.00–71.00
      Females (years*) 41.04 ± 16.38 41.00 (25.00; 53.00) 18.00–75.00
      Data are presented as n (%) for sex and mean ± SD for continuous variables. M, mean; SD, standard deviation; Me, median; IQR, interquartile range. * Only for males/females.

      Table 1. 

      Demographic characteristics of the study group.

    • Variable Correlation between age and left-eye parameters Correlation between age and right-eye parameters
      Rho p p-adj Rho p p-adj
      N75 μV 1 0.20 0.043 0.208 0.06 0.542 0.867
      N75 ms 1 0.16 0.101 0.304 0.06 0.538 0.867
      P100 μV 1 −0.18 0.061 0.244 −0.16 0.101 0.304
      P100 ms 1 −0.05 0.594 0.891 −0.03 0.743 0.892
      N175 μV 1 −0.05 0.633 0.892 0.04 0.719 0.892
      N135 ms 1 0.00 0.977 0.977 −0.10 0.327 0.654
      N75 μV 2 0.10 0.302 0.654 0.07 0.483 0.867
      N75 ms 2 0.41 < 0.001 < 0.001 0.39 < 0.001 < 0.001
      P100 μV 2 0.10 0.300 0.654 0.00 0.975 0.977
      P100 ms 2 0.28 0.004 0.029 0.20 0.039 0.208
      N135 μV 2 −0.14 0.141 0.377 −0.02 0.819 0.936
      N135 ms 2 0.02 0.864 0.943 0.04 0.678 0.892
      Rho–Spearman correlation coefficient. p-adj are the p-values corrected with Benjamini–Hochberg adjustment for multiple comparisons. Confounding factors not considered. Bold values indicate statistically significant correlations after Benjamini–Hochberg correction for multiple comparisons (p-adj < 0.05).

      Table 2. 

      Correlation between age and analyzed parameters.

    • Variable Males Females MD (95% CI) p p-adj
      n M ± SD / Me (IQR) n M ± SD / Me (IQR)
      N75 OP μV 1 53 −2.03 (−3.49; −0.69) 53 −1.98 (−4.24; −0.95) −0.05 (−0.66; 1.09) 0.565 0.678
      N75 OP ms 1 53 70.00 (66.00; 75.00) 53 71.00 (68.00; 74.00) −1.00 (−3.00; 2.00) 0.537 0.678
      P100 OP μV 1 53 8.45 (6.21; 11.27) 53 10.58 (7.19; 13.46) −2.13 (−3.02;0.23) 0.083 0.284
      P100 OP ms 1 53 101.26 ± 5.43 53 101.26 ± 6.55 0.00 (−2.32;2.32) > 0.9991 > 0.999
      N135 OP μV 1 53 −9.40 (−12.44; −6.52) 53 −11.08 (−14.92; − 7.23) 1.68 (−0.29; 3.50) 0.102 0.307
      N135 OP ms 1 53 141.53 ± 13.03 53 140.77 ± 12.98 0.75 (−4.25; 5.76) 0.7661 0.875
      N75 OP μV 2 54 −4.34 (−5.61; −2.55) 53 −4.63 (−6.48; −2.51) 0.01 (−0.69; 1.60) 0.378 0.620
      N75 OP ms 2 55 81.00 (78.00; 84.00) 53 82.00 (78.00; 87.00) −1.00 (−4.00; 1.00) 0.133 0.349
      P100 OP μV 2 55 9.64 (6.00; 13.25) 53 12.71 (7.76; 18.02) −3.07 (−5.15; −0.44) 0.021 0.196
      P100 OP ms 2 55 106.78 ± 6.46 53 108.19 ± 6.65 −1.41 (−3.91; 1.09) 0.2671 0.535
      N135 OP μV 2 54 −10.02 (−16.12; −5.95) 53 −12.45 (−16.93; −8.82) 2.43 (−0.29; 4.91) 0.077 0.284
      N135 OP ms 2 55 150.22 ± 12.78 53 154.83 ± 13.18 −4.61 (−9.57; 0.34) 0.0681 0.284
      N75 OL μV 1 54 −2.39 (−3.91; −1.09) 53 −2.75 (−4.13; −1.40) 0.36 (−0.49; 1.18) 0.413 0.620
      N75 OL ms 1 54 70.00 (65.00; 74.00) 53 71.00 (69.00; 74.00) −1.00 (−4.00; 1.00) 0.153 0.349
      P100 OL μV 1 54 8.53 (5.95; 10.74) 53 10.42 (7.19; 13.52) −1.89 (−3.18; −0.11) 0.033 0.196
      P100 OL ms 1 54 101.00 (98.00; 103.75) 53 101.00 (98.00; 104.00) 0.00 (−2.00; 2.00) 0.928 0.968
      N135 OL μV 1 54 −9.19 (−12.46; −6.97) 53 −10.63 (−14.62; − 6.91) 1.44 (−0.57; 3.45) 0.160 0.349
      N135 OL ms 1 54 141.98 ± 11.17 53 141.74 ± 13.97 0.25 (−4.60; 5.09) 0.9201 0.968
      N75 OL μV 2 54 −3.77 (−5.74; −2.65) 53 −4.45 (−6.18; −2.40) 0.68 (−0.69; 1.58) 0.515 0.678
      N75 OL ms 2 54 80.00 (76.00; 84.75) 53 82.00 (78.00; 85.00) −2.00 (−4.00; 2.00) 0.389 0.620
      P100 OL μV 2 54 9.61 (6.44; 13.54) 53 12.70 (9.13; 15.34) −3.09 (−4.81; −0.71) 0.008 0.185
      P100 OL ms 2 54 106.93 ± 7.24 53 108.08 ± 7.24 −1.15 (−3.93; 1.63) 0.4141 0.620
      N135 OL μV 2 54 −9.76 (−14.40; −7.06) 53 −13.78 (−15.77; −9.49) 4.02 (0.32;5.02) 0.028 0.196
      N135 OL ms 2 54 150.24 ± 11.93 53 151.89 ± 15.58 −1.65 (−6.96; 3.67) 0.5401 0.678
      Groups were compared with the Student t-test or the Mann–Whitney U test, as appropriate. p-adj are the p-values corrected with Benjamini–Hochberg adjustment for multiple comparisons. Confounding factors not considered. M, mean; SD, standard deviation; Me, median; IQR, interquartile range; MD, mean or median difference (males vs females); CI, confidence interval.

      Table 3. 

      Comparison of analyzed parameters between males and females.

    • Variable n M ± SD, left eye M ± SD, right eye Me (IQR), left eye Me (IQR), right eye p (Wilcoxon) ICC 95% CI for ICC p (ICC)
      N75 μV 1 105 −2.81 ± 2.42 −2.47 ± 2.55 −2.53 (−4.00; −1.16) −2.01 (−3.99; −0.83) 0.102 0.676 0.558 to 0.768 < 0.001
      N75 ms 1 105 70.27 ± 7.32 70.18 ± 7.02 70.00 (66.00; 74.00) 71.00 (68.00; 74.00) 0.861 0.431 0.262 to 0.574 < 0.001
      P100 μV 1 105 9.75 ± 4.53 10.02 ± 4.70 8.97 (6.34; 11.61) 9.07 (7.04; 12.17) 0.193 0.864 0.806 to 0.905 < 0.001
      P100 ms 1 105 100.69 ± 5.73 101.25 ± 6.01 101.00 (98.00; 104.00) 101.00 (98.00; 105.00) 0.404 0.632 0.501 to 0.734 < 0.001
      N135 μV 1 105 −10.55 ± 5.65 −10.82 ± 5.52 −9.76 (−13.62; − 6.86) −10.22 (−13.39; −6.93) 0.326 0.891 0.844 to 0.925 < 0.001
      N135 ms 1 105 141.70 ± 12.65 141.16 ± 13.01 141.00 (133.00; 148.00) 141.00 (134.00; 149.00) 0.845 0.699 0.587 to 0.785 < 0.001
      N75 μV 2 106 −4.52 ± 3.17 −4.69 ± 3.71 −4.04 (−5.89; −2.42) −4.63 (−5.90; −2.55) 0.194 0.758 0.664 to 0.829 < 0.001
      N75 ms 2 107 80.21 ± 8.19 80.85 ± 7.47 81.00 (76.50; 85.00) 81.00 (78.00; 85.00) 0.304 0.613 0.480 to 0.719 < 0.001
      P100 μV 2 107 11.70 ± 5.95 11.96 ± 6.88 10.99 (7.56; 14.21) 10.95 (6.77; 15.61) 0.283 0.890 0.844 to 0.924 < 0.001
      P100 ms 2 107 107.50 ± 7.23 107.38 ± 6.53 108.00 (103.00; 112.00) 106.00 (102.00; 112.00) 0.925 0.654 0.531 to 0.750 < 0.001
      N135 μV 2 106 −12.11 ± 6.87 −12.25 ± 7.04 −11.12 (−15.67; −7.75) −11.48 (−16.76; −7.03) 0.794 0.880 0.829 to 0.917 < 0.001
      N135 ms 2 107 151.06 ± 13.82 152.51 ± 13.18 151.00 (141.00; 162.00) 153.00 (143.50; 164.00) 0.496 0.629 0.499 to 0.731 < 0.001
      Correlations between eyes were analyzed using the Wilcoxon test and ICC. M, mean; SD, standard deviation; Me, median; IQR, interquartile range; ICC, intraclass correlation coefficient; CI, confidence interval. Bold values indicate statistically significant intraclass correlation coefficients (p < 0.05)

      Table 4. 

      Interocular correlations.