Free papers detail | 11th Asia Pacific Tele Ophthalmology Society Symposium

Title
In Vivo Three-Dimensional Optic Nerve Head Strain from Positional and Acute Intraocular Pressure Changes in Normal Tension Glaucoma

Authors
Shayne S Tan, Tingting Liu, Tun A Tin

Presenting
Shayne S Tan

PURPOSE:
To evaluate optic nerve head (ONH) strain associated with changes in body position and elevated intraocular pressure (IOP) in patients with normal tension glaucoma (NTG).

METHODS:
Optical coherence tomography (OCT) scans and IOP were obtained in NTG and healthy subjects in the sitting, supine, and lateral decubitus positions (LDP). Additionally, IOP was raised by 10-15mmHg above baseline using an ophthalmodynamometer, and maintained constant for OCT acquisition. The artificial intelligence REFLECTIVITY software (Abyss Processing Pte Ltd, Singapore) was used to automatically segment the ONH on 3D-reconstructed OCT scans to obtain neural tissue parameters (retinal nerve fibre layer (RNFL), ganglion cell complex (GCC)) and connective tissue parameters (prelaminar and laminar cribosa parameters, and peripapillary scleral angle). OCT-based 3D strain mapping technology was also used to characterise local ONH deformations.

METHODS:

Optical coherence tomography (OCT) scans and IOP were obtained in NTG and healthy subjects in the sitting, supine, and lateral decubitus positions (LDP). Additionally, IOP was raised by 10-15mmHg above baseline using an ophthalmodynamometer, and maintained constant for OCT acquisition. The artificial intelligence REFLECTIVITY software (Abyss Processing Pte Ltd, Singapore) was used to automatically segment the ONH on 3D-reconstructed OCT scans to obtain neural tissue parameters (retinal nerve fibre layer (RNFL), ganglion cell complex (GCC)) and connective tissue parameters (prelaminar and laminar cribosa parameters, and peripapillary scleral angle). OCT-based 3D strain mapping technology was also used to characterise local ONH deformations.

RESULTS:
45 NTG and 29 normal eyes were recruited. Both groups showed significant ONH strain in neural tissues in the supine and LDP positions and at elevated IOP (p<0.05), but neither showed significant connective tissue changes for these same conditions (p>0.05). Multivariate analysis showed that GCC change from sitting to supine and RNFL thickness change from baseline to elevated IOP were both associated with worsening mean deviation (β= 0.12, 95%CI, 0.05-0.20, p=0.002 and β=-0.01, 95%CI, -0.02-0.00, p=0.015 respectively), and visual field index (β = 0.34, 95%CI, 0.12-0.57, p=0.003 and β=-0.04, 95%CI, -0.07-0.01, p=0.011 respectively).

RESULTS:

45 NTG and 29 normal eyes were recruited. Both groups showed significant ONH strain in neural tissues in the supine and LDP positions and at elevated IOP (p<0.05), but neither showed significant connective tissue changes for these same conditions (p>0.05). Multivariate analysis showed that GCC change from sitting to supine and RNFL thickness change from baseline to elevated IOP were both associated with worsening mean deviation (β= 0.12, 95%CI, 0.05-0.20, p=0.002 and β=-0.01, 95%CI, -0.02-0.00, p=0.015 respectively), and visual field index (β = 0.34, 95%CI, 0.12-0.57, p=0.003 and β=-0.04, 95%CI, -0.07-0.01, p=0.011 respectively).

CONCLUSIONS:
ONH neural tissues are more sensitive to IOP changes compared to connective tissues. Posture-induced GCC changes and IOP-induced RNFL changes are associated with worsening visual field deficits in NTG eyes.