[Identification and removal of orbital foreign bodies using the CAS (Computer-Assisted-Surgery) system].

Identification and extraction of orbital foreign bodies can cause problems in special cases. Small, retroocular localized fragments can be hard to detect, severe bleeding and traumatically damaged anatomy can render orientation difficult. At the Department of Otolaryngology, Plastic Head and Neck Surgery of Aachen University Hospital we used the investigational new CAS (Computer-Assisted-Surgery) device in several such cases with good success. CAS is a new localizing technique designed to assist the head and neck surgeon during surgery providing real-time position information. The method is based upon a three dimensional volume model of the patient's skull generated by preceding computed tomography imaging procedures such as CT or MRI scan. Intraoperative correlation of 3D-model and the patient's skull allows for real-time position display of a surgical instrument on the monitor screen. Accuracy of the method has been experimentally determined to be within 1 mm. Thereby the surgeon is able to localize even small foreign bodies without extensive exploration. In the case of multiple foreign bodies the surgeon gets a simple documentation facility, which of the visible fragments have already been extracted. Medially placed foreign bodies could be removed via an endonasal approach. Encouraged by these results we recommend CAS for the extraction of orbital foreign bodies.