What causes oil droplet appearance in the eye on CT?
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Answer:
Round, hypodense fat droplets floating non-dependently within the anterior chamber or vitreous represent herniated intraocular fat following globe rupture (open globe injury) or, less commonly, intraocular surgery, where orbital fat prolapses into the globe through a scleral or capsular defect and floats toward the anterior segment because it is less dense than the surrounding aqueous or vitreous.
Why is it called so?
Named for the characteristic appearance of small, round, hypodense droplets resembling oil droplets floating in fluid on CT.
Pathophysiology
Trauma (or, rarely, surgery) disrupts the integrity of the sclera/ocular capsule, allowing orbital fat to prolapse into the globe. Fat measures approximately -100 to -70 Hounsfield units (HU), distinctly hypodense compared with the aqueous humor and vitreous (approximately 0 to +20 HU). Being less dense than the surrounding ocular fluid, the fat droplets float non-dependently, layering toward the anterior chamber in a supine patient on CT, forming discrete rounded hypodense globules — a specific, though not universally sensitive, sign of globe rupture.
Alternative names: None
Other associated named signs: Other CT signs of globe rupture include altered globe contour/volume loss (“flat tire” appearance), scleral wall discontinuity, and intraocular foreign bodies.
References
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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