Evaluation of the Microvascular Blood Flow, Oxygenation, and Survival of Tarsoconjunctival Flaps Following the Modified Hughes Procedure.

Abstract

For the modified Hughes procedure, a tarsoconjunctival flap from the upper eyelid is used to reconstruct large, full-thickness, lower eyelid defects. The conjunctival pedicle is divided once vascularization is deemed to be adequate. The importance of maintaining a flap pedicle to ensure adequate perfusion of the graft has been questioned. The purpose of the study was to investigate the microvascular blood flow, oxygenation, and survival of a tarsoconjunctival flap in an experimental porcine model of the modified Hughes procedure. The modified Hughes procedure was performed in 9 pigs. Microvascular blood flow was measured by laser Doppler velocimetry. Tissue oxygenation was measured using a Licox system, and tissue survival was determined by analyzing histologic sections of biopsy specimens from the lower edge of the flap. Blood flow and the oxygenation of the tissue decreased gradually during dissection and advancement of the tarsoconjunctival flap. At the time when the flap was sutured into place, there was virtually no blood flow or oxygenation of the tissue. However, flap survival did not seem to be compromised, as shown by the absence of pyknotic cell nuclei necrosis in the biopsy specimens, 12 hours after the procedure. The pedicle of the tarsoconjunctival flap does not seem to contribute to the nourishment of the tarsoconjunctival flap. Nourishment may be supplied by the rich vascularization of the remaining eyelid and tear film. If this is the case, single-stage grafting of a free tarsal plate may be performed, thus avoiding the eyelid-sharing stage of the procedure, without compromising the survival of the graft.