Optic Nerve Stretch in Dysthyroid Optic Neuropathy: A Systematic Review and Meta-Analysis

Area of Science:

• Ophthalmology
• Radiology
• Endocrinology

Background:

• Dysthyroid optic neuropathy (DON) is a vision-threatening complication of thyroid eye disease.
• The role of optic nerve stretch (ONS) in DON pathophysiology is debated.
• Imaging plays a crucial role in understanding orbital and optic nerve changes.

Purpose of the Study:

• To systematically review and assess imaging evidence of optic nerve stretch (ONS) in dysthyroid optic neuropathy (DON).
• To evaluate the prevalence, measurement techniques, and potential association of ONS with DON.
• To clarify the contribution of ONS to DON pathogenesis.

Main Methods:

• Systematic review of studies using CT or MRI for ONS in thyroid eye disease.
• Searches conducted in PubMed, EMBASE, Cochrane CENTRAL, and ClinicalTrials.gov.
• Pooled proportions calculated using random-effects models; heterogeneity assessed with I2.

Main Results:

• Sixteen studies (1,277 orbits) were included; 508 with DON and 769 without.
• Optic nerve stretch was reported in 56% of DON orbits versus 31% of non-DON orbits (high heterogeneity).
• ONS was associated with apical crowding, but not consistently established as an independent cause of DON.

Conclusions:

• Optic nerve stretch is frequently observed in DON but its causal role is uncertain.
• ONS may be a consequence of orbital soft-tissue expansion rather than a primary driver of DON.
• Apical compression and microvascular ischemia remain the likely principal mechanisms for DON.