Orbit: Canthal Advancement and Balanced Orbital Decompression

Abstract

Thyroid eye disease causes orbital congestion and proptosis due to extraocular muscle and orbital fat enlargement with inflammation, edema, deposition of glycosaminoglycans and fibrosis. The disparity in bony orbital volume and the soft tissue accumulation may lead to compressive optic neuropathy and exposure keratopathy. Surgical treatment of the proptosis from thyroid eye disease consists of removal of the nonessential orbital bone or orbital decompression. Removal of the nonsupporting orbital bone allows the surgeon to take advantage of the adjacent sinus spaces and the temporal fossa to expand orbital volume. For cases of mild to moderate proptosis, medial and lateral wall removal may be performed, acquiring additional space from the adjacent ethmoid sinuses and the temporal fossa behind the lateral orbital rim. Additional volume may be obtained from removal of the medial orbital floor and anterior displacement of the lateral orbital rim. Reset of the lateral canthus on the advanced rim may also provide improvement of lid position and cosmetic appearance. Patients should be educated about the risks, benefits, and alternatives of the procedure including bleeding, infection, scar, paresthesias, loss of vision, double vision, and need for more surgery. A balanced medial and lateral wall decompression may reduce the risk of diplopia by mechanically preventing unilateral horizontal displacement of the orbital contents. Sparing the medial orbital strut diminishes the risk of downward dystopia of the globe.