Abstract
Purpose :
To analyse optic nerve sheath (ONS) dynamics from transorbital ultrasound and investigate a potential difference between the patients with normal tension (NTG), primary open angle glaucoma (POAG) and controls.
Methods :
The study included 42 patients with NTG, 43 with POAG and 40 healthy controls. B-scan ultrasound was performed binocularly, using a 12.5 MHz linear array probe. The transverse motion on each side of the ONS was estimated from ultrasound. Corresponding to the heart rate, fourier analysis was used to extract the magnitude of the displacement. The measurement of ONS deformation was obtained by calculating the normalized absolute difference between the displacements on each side of the ONS. This parameter was referred to as the deformability index, which is inversely related to stiffness. The one-sided Mann-Whitney U test was used for statistical comparison.
Results :
The deformability index in NTG (0.11±0.05) was significantly lower than that in the POAG (0.20±0.06, p=0.008) or control (0.21±0.04; p=0.006) groups. The deformability indexes in the POAG and control groups were not significantly different (p = 0.15).
Conclusions :
We assessed the ONS pulsatile dynamics using transorbital ultrasound imaging and found that the deformability index is lower in NTG as compared to normal control. This is compatible with a lower cerebrospinal fluid pressure in the optic nerve in NTG，implying that trans-lamina cribrosa pressure difference might be abnormally higher in NTG group than in normal control.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.