The Bubble Eye Sign: Understanding the Radiological Imaging of Gas inside the Orbit

Gas, appears as radiolucent on X-ray, is normally absent in the orbit. However, intraocular surgeries occasionally utilize retained intraocular gas for tamponade effect. Intravitreal gas persists after retinal surgery, being confounded by the scleral shell of the operated eye, outlines the shape of the eyeball, and gives the characteristic bubble appearance on skull X-ray. This is different from orbital emphysema caused by orbital fracture when gas is located outside the globe but confined by the orbit, giving a crescent or concave shape over the superior orbit usually. Falls is common after intraocular retinal surgeries due to change of usual stereopsis, prolonged prone posturing, and other systemic comorbidities. By identifying the "Bubble Eye sign" described, attending physician should alert the presence of intravitreal gas, most commonly iatrogenic. Further ophthalmological history taking and examinations are thus indicated, instead of exposing patients to unnecessary radiation under computed tomography scan for orbital fracture investigation.