Orbit MRI
A small space with the optic nerve, muscles and vessels packed together — MRI’s soft-tissue detail (with fat suppression) is what makes orbital problems legible.
The optic nerve
MRI is the test for optic neuritis — nerve enhancement and T2 signal — and, importantly, the brain is imaged at the same time to look for demyelinating lesions, since optic neuritis can herald multiple sclerosis. It also assesses compressive lesions along the nerve and chiasm.
Masses & thyroid eye disease
- Orbital masses: cavernous venous malformation, lymphoma, optic nerve sheath meningioma and glioma, lacrimal gland lesions, metastases — MRI localises (intraconal vs extraconal) and characterises.
- Thyroid eye disease: enlargement of the extraocular muscles (sparing the tendons), with active-phase oedema on STIR that can guide treatment timing.
Spread & the apex
MRI shows perineural and intracranial extension, cavernous sinus involvement, and orbital apex disease better than CT. CT remains preferred for acute trauma, bony detail and detecting calcification/foreign bodies (and MRI is contraindicated with a suspected metallic intra-ocular foreign body).
Reference: Tailor TD et al. Orbital neoplasms in adults: clinical, radiologic, and pathologic review. RadioGraphics 2013;33:1739–58.
Educational summary for clinicians; correlate with ophthalmology. Not medical advice.