Ultrasound biomicroscopic diagnosis of scleral foreign bodies

Small intrascleral foreign bodies of different materials, especially plastic or organic, can sometimes not easily--or not at all--be detected by routine X-ray examination or computed tomography scan. The aim of our study was to evaluate the usefulness of ultrasound biomicroscopy (UBM) with regard to the detection and localisation of such foreign bodies. An in vitro study with the preparation of a scleral tunnel on 12 porcine eyes was performed. Small foreign bodies of different types of material were placed in the tunnel. The UBM was performed with a Humphrey Ultrasound Biomicroscope, Model 840, to evaluate its diagnostic value in detecting and specifying these sclera-covered foreign bodies. Even small foreign bodies of the anterior ocular segment of only 200 microm in size can be detected with the UBM due to the typical ultrasound patterns and artifacts. However, there is no diagnostic specificity for the corresponding material. The UBM is a high-frequency ultrasonic device with an imaging depth of 5 mm and a spatial resolution of 100 microm. Therefore it is a useful alternative or, respectively, additional diagnostic tool to common imaging techniques like routine X-ray imaging or CT scans, especially in the detection of non-metallic objects. It can provide important information for the ophthalmic surgeon with regard to pre-operative evaluation of the eye. Furthermore, the UBM might even substitute operative exploration of foreign bodies if they are located in the anterior segment of the eye.