Fig. 16. A. After membrane dissection is completed, a fluid–gas exchange may be performed to determine if enough traction has been relieved to permit settling of the retina. B. One must be vigilant for persistent traction during the exchange. Continuation of tamponade infusion in the presence of persistent traction may result in enlargement of preexisting breaks, the creation of new breaks (large arrow), or subretinal movement of the tamponade.