PT - JOURNAL ARTICLE AU - Thanadet Chuangsuwanich AU - Tin A. Tun AU - Fabian A. Braeu AU - Xiaofei Wang AU - Zhi Yun Chin AU - Satish K. Panda AU - Martin Buist AU - Dan Milea AU - Nicholas Strouthidis AU - Shamira A. Perera AU - Monisha E. Nongpiur AU - Tin Aung AU - Michael JA Girard TI - Adduction Induces Large Optic Nerve Head Deformations in Subjects with Normal Tension Glaucoma AID - 10.1101/2021.08.25.457300 DP - 2022 Jan 01 TA - bioRxiv PG - 2021.08.25.457300 4099 - http://biorxiv.org/content/early/2022/04/26/2021.08.25.457300.short 4100 - http://biorxiv.org/content/early/2022/04/26/2021.08.25.457300.full AB - Purpose: To assess optic nerve head (ONH) deformations and strains during adduction, abduction, and intraocular pressure (IOP) elevation in subjects with high-tension glaucoma (HTG) and normal-tension glaucoma (NTG). Design: Clinic-based cross-sectional study. Participants: 114 HTG subjects and 114 NTG subjects. Methods. We recruited 228 subjects (114 subjects with HTG [pre-treatment IOP > 21mmHg] and 114 with NTG [pre-treatment IOP < 21mmHg]). For each subject, we imaged the ONH using spectral-domain optical coherence tomography (OCT) under the following conditions: (1) primary gaze, (2) 20 degree adduction, (3) 20 degree abduction, and (4) primary gaze with acute IOP elevation (to approximately 33 mmHg) achieved through ophthalmodynamometry. For each OCT volume, we automatically segmented the prelaminar tissue (PLT), the choroid, the sclera and the lamina cribrosa (LC) using a deep learning algorithm. We also digitally aligned the OCT volumes obtained from (2)-(4) to the primary gaze volume (1) before performing digital volume correlation (DVC) analysis to quantify IOP- and gaze-induced ONH tissues three-dimensional displacements and effective strain (a local measure of tissue deformation) for all scenarios. Main Outcome Measures: Three-dimensional ONH displacements and strains. Results: Across all subjects, adduction generated high effective strain (4.2 ± 1.4%) in the ONH tissues with no significant difference (p>0.05) with those induced by IOP elevation (4.5 ± 1.5%); while abduction generated significantly lower (p = 0.014) effective strain (3.8 ± 1.1%). Interestingly, the LC of HTG subjects exhibited significantly higher effective strain than those of NTG subjects under IOP elevation (HTG:4.6 ± 1.7% vs NTG:4.1 ± 1.5%, p = 0.047). Conversely, the LC tissue of NTG subjects exhibited significantly higher effective strain than those of HTG subjects under adduction (NTG: 4.9 ± 1.9% vs HTG: 4.0 ± 1.4%, p = 0.041). Conclusion: We found that adduction produced comparable strains and displacements as IOP elevation. We also found that NTG subjects experienced higher strains due to adduction than HTG subjects, while HTG subjects experienced higher strain due to IOP elevation than NTG subjects - and that these differences were most pronounced in the LC tissue.Competing Interest StatementThe authors have declared no competing interest.