Optic Nerve Traction During Adduction in Open Angle Glaucoma with Normal versus Elevated Intraocular Pressure

Area of Science:

• Ophthalmology
• Neuro-ophthalmology
• Medical Imaging

Background:

• Open angle glaucoma (OAG) is a leading cause of irreversible blindness.
• The role of optic nerve (ON) traction during eye movements in OAG pathogenesis is under investigation.
• Intraocular pressure (IOP) is a primary risk factor, but other factors may contribute to ON damage.

Purpose of the Study:

• To investigate the effects of intraocular pressure (IOP), race, and eye movement on optic nerve (ON) traction in open angle glaucoma (OAG) using magnetic resonance imaging (MRI).
• To explore whether ON traction in adduction is associated with neuropathic changes in OAG.
• To analyze the relationship between ON path length, globe translation, and OAG status.

Main Methods:

• Thirty-five OAG patients and 48 controls underwent MRI scans in various gaze positions (central, abduction, adduction).
• Generalized estimating equations were used to analyze the effects of OAG, IOP levels, adduction angle, race, age, and gender on ON path length and globe translation.
• MRI data were analyzed for differences in ON path and globe movement during eye adduction.

Main Results:

• In central gaze, ON path was more redundant in OAG patients compared to controls.
• During adduction, ONs became straighter in both groups, but globes retracted significantly only in OAG patients (P < 0.005).
• Globe retraction in adduction was more pronounced in Asian OAG patients than in white OAG patients (P < 0.02) and was independent of IOP levels.

Conclusions:

• Progressive eye adduction is associated with abnormal globe retraction in OAG, irrespective of IOP.
• This globe retraction phenomenon is more prominent in Asian individuals with OAG.
• Repetitive strain injury to the ON and peripapillary sclera due to adduction traction may contribute to OAG neuropathy independently of IOP.