Navigated Transconjunctival Endoscopic Approaches to the Orbit

Abstract

ABSTRACT BACKGROUND Standard cranial approaches to the orbit involve lengthy skin incisions, extensive soft tissue dissection, and large craniotomies, increasing morbidity. OBJECTIVE To evaluate less invasive approaches to the orbit, using endoscopic transconjunctival approaches. METHODS Neuronavigated transconjunctival approaches to the orbit were performed on 4 cadavers using 30°/3 mm and 0°/6 mm rigid endoscopes. A special head frame was designed for this study to prevent excessive movement of the endoscope tip in the orbit. Lateral and medial transconjunctival supra- and infrabulbar approaches to the extra- and intraconal spaces were performed. The incision length, maximal penetration depth in the extra- and intraconal spaces, and distance from the orbital rim to the optic nerve were measured. RESULTS All 4 approaches afforded satisfactory exposure and access to the extra- and intraconal spaces. The mean incision length for the transconjunctival approach was 10.4 mm. The optic nerve could be exposed through all 4 approaches. The mean maximal penetration depths in the extraconal space were 28.6 ± 3.5 mm for the 30°/3 mm and 20.7 ± 4.5 mm for the 0°/6 mm endoscope. In the intraconal space, the mean maximal depth of penetration was 23.8 ± 2.4 mm for the 30°/3 mm and 19.4 ± 3.4 mm for the 0°/6 mm endoscope. Based on these measurements, the orbit was classified into quadrants and zones. CONCLUSION Transconjunctival endoscopic approaches to the orbit allow maximal exposure of the extra- and intraconal spaces through a minimally invasive approach requiring no muscle transection. Infrabulbar approaches have better cosmetic results than suprabulbar approaches, which require incision of the eyelid.