In patients, the mean ONSD of right and left eyes were 0.408[+ or -]0.064 mm and 0.417[+ or -]0.065 mm, respectively.
Post-hoc analysis showed that the ONSD values of both eyes were increasing by age only in the control group (p<0.05).
It was found that only in the right eyes of patients, the ONSD values were inversely associated with GCS score (p<0.05) ONSD values increased as the GCS score decreased (Figure 1).
Analysis showed that in both eyes, there was a positive correlation between ONSD and arterial blood pressures in patients.
Normality of the distributions was assessed with the Shapiro-Wilk Normality Test; according to the result of normality analysis, Student's f-test or Wilcoxon test were used to compare mean ONSD values differences.
Based on ONSD normative values reported in the literature , a priori power analysis was performed by means of Wilcoxon-Mann-Whitney tests (a priori computed required sample size).
In the control group, mean ONSD was 0.45 [+ or -] 0.03 cm for right side and 0.45 [+ or -] 0.02 cm for left side.
After BD occurrence, ONSD was further significantly markedly increased, greater than 0.7 cm (RT 0.7 [+ or -] 0.02 cm; LT 0.71 [+ or -] 0.02 cm; p < 0.000) in respect to the pre-BD phase, except for the 2 patients who had submitted to decompressive craniectomy, in whom ONSD was substantially unchanged (before BD: RT 0.56 [+ or -] 0.01 cm; LT 0.57 [+ or -] 0.01 cm.
An M-Turbo ultrasonographic system (SonoSite, Bothell, WA) equipped with a high-frequency linear transducer was used for the ONSD and PLR measurements, while a 2.5 MHz wide-phase array transducer with an appropriate software program was utilized to perform TCCD measurements.
ONSD was measured by using an oblique axial view to access the optic nerve head 2 to 3 mm posterior to the papilla as previously described in the literature [4, 5, 8].
Differences between the values of the studied neuromonitoring indices (PI, ONSD, and V) at baseline compared to our higher volume reference value (1 mL) were evaluated by paired t-test.
ICP, ONSD, and PI were all significantly increased at 1 mL volume of epidural hematoma compared to baseline values.