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Ultrasound biomicroscopy (UBM) has been proved to be a valuable investigative tool in the evaluation of suspected anterior segment ocular foreign bodies.1 This is especially so in cases involving small, non-metallic objects and where the foreign body is not visible by slit lamp biomicroscopic examination or where a clear history of trauma is not forthcoming.
A 51 year old fisherman presented to the ophthalmic casualty department with a 2 week history of localised discomfort and redness on the temporal aspect of his right eye. He had no significant ophthalmic history and did not give a history of trauma.
Slit lamp examination of the anterior segment was unremarkable on the left side and revealed an inflamed nodular mass on the temporal aspect of the right sclera (Fig 1).
There was no visible foreign body or conjunctival tear in that region. At this point the suspected clinical diagnoses included inflammatory nodular scleritis and a lymphoma or other neoplastic mass. The patient was referred to the ophthalmic ultrasound clinic for UBM (Fig 2).
UBM revealed a high reflectivity discrete echo source (arrow) embedded deep in the sclera, surrounded by a low reflective mass (granuloma).
The appearance was consistent with a foreign body and, on direct questioning, the patient admitted to possible injury while filleting fish on his boat. An excisional biopsy was performed under local anaesthesia. Postoperative recovery was uneventful on a topical regimen of Betnesol-N eye ointment four times daily for 2 weeks; the patient’s symptoms ceased after that.
Serial sectioning and histopathological examination were carried out. This revealed a florid foreign body granulomatous reaction directed against some degenerate material of animal origin. In several levels a barbed cellular structure highly suggestive of a fishscale was seen (Fig 3).
UBM is a high resolution ultrasound using high frequency transducers (50–100 MHz) that was developed by Pavlin et al in 1990.2 It is a non-specific imaging technique that allows a highly magnified image of the anterior segment to be obtained. It is capable of producing images in the living human eye to a depth of approximately 4 mm at an axial and lateral resolution approaching 20 μm.2
The high resolution provided by this technique combined with its non-invasive and non-ionising nature make UBM a very attractive investigational method in the evaluation of suspected anterior segment foreign bodies. This is so even when no clearcut history of trauma is forthcoming as evidenced by this fisherman’s tale and the fact that UBM has been used successfully in the past to demonstrate ocular surface and intraocular foreign bodies.2,3
In this case UBM enabled us to obtain sub-surface images of the conjunctiva and sclera at the area of interest that was not possible with slit lamp biomicroscopy. It actually influenced management by raising the suspicion of a foreign body and justifying an excisional biopsy and its subsequent deeper histological sectioning when, clinically, a provisional diagnosis of conjunctival lymphoma or another neoplasm was being pursued that would not have necessarily been treated by an excisional biopsy.
We recommend the use of UBM in some cases of suspected foreign bodies in the sub-surfaces of the conjunctiva and sclera when the nature and extent of the lesion is in doubt.
Sources of funding: None.
Proprietary or financial interest: None.
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