PURPOSE - To explore the feasibility of designing, constructing, and testing an orbital endoscope for use with the free electron laser (FEL).
METHODS - An experimental study with an author-designed laser delivery system through an endoscope was conducted. Two adult pig cadavers and 6 fresh human cadavers had orbital endoscopy performed to develop a method of optic nerve sheath fenestration (ONSF) with the FEL. Twelve orbits were used to develop the surgical procedure by comparing visualization media and surgical technique. In the first 7 trials, a different variable was changed; the procedure was then refined in the human cadaver experiments. An ONSF was performed with the FEL (6.45 microm, 30 Hz, 2 to 3 mJ, 250-microm spot size) through a glass hollow wave guide introduced through an endoscope in 4 human cadaver orbits.
RESULTS - Visualization of the orbital structures was clearest with carbon dioxide; sodium hyaluronate did not displace the fat, and saline hydrated the orbital fat. Biopsy forceps alone did not produce a dural window in the four trials that used the forceps. A dural window was made by using the FEL through a glass hollow wave guide adapted to the Olympus HYF-XP endoscope in the second, third, fifth, and sixth human trials with the FEL. Histologic evidence of the ONSF was produced.
CONCLUSIONS - A hollow wave guide capable of transmitting the FEL through an endoscope was successfully constructed. ONSF with the FEL applied through an endoscope is technically feasible. Additional studies are currently examining techniques to improve intraorbital endoscopy.