Figure 1.
A–E. Frame alignment errors with frame tilt −18° (counter clockwise). Rod aligned to –A, vertical; B, lateral side; C, upper right corner; D, upper left corner; E, upper side. A mirror set of errors is generated with the frame tilt clockwise (+18°). F, shaded −9° sectors used to quantify the corresponding alignment strategies in A–E; unshaded–sectors classified as ‘other’. Sectors marked + frame tilt +18°; sectors marked – frame tilt −18°.
Figure 2.
Distribution of mean absolute errors.
Grade 2 (black bars), Grade 4 (grey bars), Grade 6 (open bars) - (n = 419 in each Grade).
Table 1.
Mean absolute errors recorded for subjects at 2 year intervals.
Figure 3.
Percentage of subjects having mean absolute errors greater than 5°.
Female - light bars; male - dark bars. Error bars show 95% CIs calculated using the Wilson method [16].
Figure 4.
Individual changes in absolute errors.
Plot of the change in absolute error between Grade 2 and Grade 6 against the initial Grade 2 error for control subjects. The solid line indicates zero error, the dotted line indicates the frame angle (18°).
Figure 5.
Distribution of signed mean errors.
A, Grade 2 (age 7–8 years); B, Grade 4 (age 9–10 years); C, Grade 6 (11–12 years). Open bars – counter clockwise frame tilt; filled bars – clockwise frame tilt. (n = 419 in all cases).
Figure 6.
Distribution of individual iMean errors and iSDs in Grade 6.
Scatterplot of iMean signed alignment error against iSD, for those subjects having iMean values between −36° and +36°, and iSD values less than 12°. Open symbols frame tilt −18° (n = 403), filled symbols frame tilt +18° (n = 401).
Table 2.
Subjects exhibiting negative frame effects at the three Grades of testing.
Table 3.
Subjects showing strong negative frame effects at Grade 6.
Table 4.
Frequency of identified alignment strategies used by subjects having iSD >9° at each Grade.
Table 5.
Average times per presentation recorded at 2-year intervals.