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Optic Nerve Tortuosity and Globe Proptosis in Normal and Glaucoma Subjects

Wang, Xiaofei PhD*,†; Rumpel, Helmut PhD; Baskaran, Mani DNB, PhD§,∥; Tun, Tin A. MD†,§; Strouthidis, Nicholas FRCS(Ed), PhD§,¶,#; Perera, Shamira A. FRCOphth§,∥; Nongpiur, Monisha E. MD, PhD§,∥; Lim, Winston E.H. MBBS, FRCR; Aung, Tin FRCS(Ed), PhD§,∥,**; Milea, Dan MD, PhD§,∥; Girard, Michaël J.A. PhD†,§

doi: 10.1097/IJG.0000000000001270
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Précis: Eyes with glaucoma have tauter optic nerves compared with normal eyes, which may exert more force on the optic nerve head tissues during eye movements.

Purpose: The purpose of this study was to assess the difference in optic nerve tortuosity during eye movements and globe proptosis between primary open angle glaucoma and normal subjects using orbital magnetic resonance imaging (MRI).

Methods: Ten Chinese subjects matched for ethnicity and refractive errors were recruited, including 5 normal controls and 5 patients with primary open angle glaucoma. All subjects underwent MRI to assess their optic nerves and globes for 3 eye positions: primary gaze, adduction, and abduction. Optic nerve tortuosity (optic nerve length divided by the distance between 2 ends) and globe proptosis (maximum distance between the cornea and interzygomatic line) were measured from MRI images.

Results: In adduction, the tortuosity of normal eyes was significantly larger than that of the glaucomatous eyes. Optic nerve tortuosity in adduction in the control and glaucoma groups were 1.004±0.003 (mean±SD) and 1.001±0.001, respectively (P=0.037). Globe proptosis (primary gaze) in glaucoma subjects (19.14±2.11 mm) was significantly higher than that in control subjects (15.32±2.79 mm; P=0.046).

Conclusions: In this sample, subjects with glaucoma exhibited tauter optic nerves and more protruding eye globes compared with normal eyes. This may impact optic nerve head deformations in anatomically predisposed patients.

*Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China

Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, Faculty of Engineering

**Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore

Department of Diagnostic Radiology, Singapore General Hospital

§Singapore Eye Research Institute, Singapore National Eye Centre

Duke-NUS Medical School, Singapore, Singapore

NIHR Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK

#Discipline of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney, NSW, Australia

Disclosure: M.J.A.G. acknowledges support from the Singapore Eye Research Institute Pilot Grant (R1228/34/2015) and from an NUS Young Investigator Award (NUSYIA_FY13_P03, R-397-000-174-133). X.W. acknowledges support from Beijing Municipal Natural Science Foundation (7194288). The remaining authors declare no conflict of interest.

Reprints: Michaël J.A. Girard, PhD, Ophthalmic Engineering & Innovation Laboratory, Department of Biomedical Engineering, National University of Singapore, Engineering Block 4, #04-8, 4 Engineering Drive 3, Singapore 117583, Singapore (e-mail: mgirard@nus.edu.sg).

Received August 24, 2018

Accepted April 13, 2019

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