Abstract
An 81-year-old man was taken to Accident & Emergency after a fall. CT brain imaging demonstrated a well-defined, homogenous, hyperdense mass in the posterior segment of the left eye. Reported as vitreous haemorrhage, an urgent ophthalmological assessment was instigated.
Detailed history revealed previous vitreoretinal procedures for multiple retinal detachments. Ophthalmological examination confirmed presence of silicone oil in this eye.
The appearance of silicone oil in the eye has become an increasingly prevalent finding given its continued use in complex vitreoretinal procedures since 1962. Clinicians regularly interpreting orbital, facial and brain imaging need to be aware of these imaging appearances to prevent diagnostic confusion.
Keywords: retina, radiology
Background
The appearance of intraocular silicone oil on CT can potentially mimic orbital pathology, such as vitreous haemorrhage. To differentiate pathology on imaging, it is important to be aware that the lower physical density of oil means that it floats in water. This gives the distinctive appearance of a hyperdense mass anterior to a low-density crescent seen on axial CT imaging of the supine patient.1
Case presentation
An 81-year-old man was taken to Accident & Emergency after an unexplained fall. Medical history, examination and CT scan of the brain were performed.
Investigations
CT imaging demonstrated a well-defined, homogenous, hyperdense mass in the posterior segment of the left eye (figure 1).
Figure 1.
Axial CT image demonstrating the appearance of intraocular silicone oil in the left eye.
Differential diagnosis
Differential diagnoses of a well-defined, homogenous, hyperdense mass in the posterior segment of the left eye:
Retinoblastoma.
Lymphoma.
Metastasis.
Silicone oil.
Vitreous haemorrhage.
Treatment
The CT brain was reported as vitreous haemorrhage and an urgent ophthalmological assessment was instigated. Detailed ophthalmic history revealed previous vitreoretinal procedures for retinal detachment when the patient was aged 55 years old. Ophthalmological examination confirmed presence of silicone oil in this eye.
Outcome and follow-up
The patient was reassured that the CT did not demonstrate any new or concerning intraocular pathology.
Discussion
The use of silicone oil for the treatment of retinal detachment was first described in 1962.2 It is used as intraocular tamponade in complicated and high-risk retinal detachment. Cases such as retinal detachment associated with severe proliferative vitreoretinopathy or resulting from viral retinitis3 are clinical scenarios where silicone oil is used. Ideally, the silicone oil is removed once the retina is stable; however, in some cases it is necessary to leave in situ to maintain ocular integrity and prevent phthisis.
As the mass is well defined, homogenous and hyperdense, the possibility of neoplasm is less likely.
To differentiate from vitreous haemorrhage, it is important to be aware that the lower physical density of oil means that it floats in water. This gives the distinctive appearance of a hyperdense mass anterior to a low-density crescent seen on axial CT imaging of the supine patient.1 MRI can also be helpful in confirming the diagnosis. Silicone oil appears hyperintense on T1-weighted images and has variable signal intensities on T2 weighting.4 T2-weighted images also produce an artefact named chemical shift. Resulting from the interface between water and silicone, this can further aid interpretation.
Learning points.
A detailed and accurate clinical history, including any ophthalmic history, is always necessary.
Silicone oil intraocular tamponade is regularly used in vitreoretinal surgery.
Silicone oil in orbital imaging is an increasing finding. Knowledge of silicone oil’s distinctive appearance on CT can prevent unnecessary alarm.
Footnotes
Contributors: SH wrote the case report. ST wrote the radiological findings part of the manuscript. MSB reviewed and edited the case report.
Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests: None declared.
Patient consent: Obtained.
Provenance and peer review: Not commissioned; externally peer reviewed.
References
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