Figure 1.
Schematic drawing of the tactile acuity charts containing dot patterns (A) and Landolt rings (B).
Due to the micro-manufacturing procedure of the polymer material, the test patterns had to be fitted in a circular sheet. The size of the characters varied between lines from 0.0 (i.e., standard Braille spacing) to −0.5 log units for the dot patterns and from −0.3 to −0.7 log units for the ring patterns. The additional thermo-sensitive A4 paper versions also included lines with larger spacings up to +0.3 log units. All lines except those with the largest spacing contained 8 characters each.
Figure 2.
Mean tactile acuities in the prestudy.
Acuity thresholds (with standard errors) obtained with the dot pattern and Landolt ring charts are shown separately for the thermo-sensitive paper (red) and polymer (blue) versions.
Figure 3.
Percentage of correct identifications for the four character orientations in the prestudy.
Percentages refer to correct character identifications across all lines of the polymer versions (blue) and across the corresponding lines of the paper versions (red). Character orientations refer to upper left or j (1), upper right or h (2), lower right or f (3), and lower left or d (4), for the dot charts, and top (1), right (2), bottom (3), and left (4), for the Landolt ring charts. Error bars denote standard errors of the mean.
Figure 4.
Mean tactile acuities in the main study.
Acuity thresholds (with standard errors) obtained with the dot pattern and Landolt ring charts, the two-point threshold, and the GOT, are shown separately for the first (brown) and second (grey) measurement.
Table 1.
Repeatability Estimates for the Tactile Acuity Measures Used in the Main Study.
Figure 5.
Repeated measures of tactile acuity.
Panels show m-d-plots for the dot pattern and Landolt ring acuity charts, two-point thresholds, and GOT, respectively. Individual averages of the two measurements for each method are plotted against their differences (session 2 minus session 1). Horizontal lines indicate zero difference between the two measurements.
Table 2.
Summary of Intercorrelations for the Mean Acuities Obtained with the Dot Pattern and Landolt Ring Acuity Charts, the Two-Point Threshold, and the GOT.
Figure 6.
Pairwise comparisons between dot pattern and Landolt ring acuity charts, two-point thresholds, and GOT.
For each of the six comparisons, m-d-plots show individual averages of the mean thresholds obtained by the two respective methods against their differences (last-mentioned minus first-mentioned method, respectively). Solid lines indicate 95% limits of agreement. For regression-based limits of agreement, dotted lines additionally indicate the mean differences between methods.
Table 3.
Factor Loadings and Communalities Based on a Principal Component Analysis with Varimax Rotation for the Four Tactile Acuity Measures.