Perfusion Monitoring During Oculoplastic Reconstructive Surgery - Opportunities for Optimization of Surgical Techniques

Abstract: Existing oculoplastic reconstructive surgical techniques are based on empirical knowledge and were established long before perfusion monitoring was possible. It is believed that an avascular graft should always be placed on a vascular bed or flap and also that the viable length of a flap depends on the width of its pedicle. The actual role of the length, width and thickness of a random flap in its survival is still not clear. Modern imaging techniques now enable monitoring of perfusion and reconsideration of how to optimize the reconstructive surgical procedures. In the present thesis, different surgical techniques were studied, namely tarsoconjunctival flaps using the modified Hughes procedure, random pattern skin advancement flaps and full-thickness eyelid axial flaps. Perfusion was assessed using laser Doppler velocimetry, laser speckel, thermography and tissue oxygenation (pO2) measurements.The results from the tarsoconjunctival flaps in pigs (Paper I) showed that perfusion decreased gradually during dissection and advancement of the tarsoconjunctival flap. At the time when the flap was sutured into placed, there was virtually no perfusion or oxygenation of the distal end of the flap. A recent study shows that the same is true for tarsoconjunctival flaps in patients (Paper II). Using a free eyelid composite graft may be an alternative reconstructive surgical technique and this has now been performed in a first case (Paper III).The results from the random pattern advancement skin flaps in pigs (Paper IV) show that the flap length may be more important than the length to width ratio. Perfusion decreased gradually from the base to the tip of the flap, reaching ~20% at 2.5 cm from the base of the flap, with virtually no perfusion 3.0 cm from the base of the flap. Making the flap longer does not seem meaningful and a free transplant may then be considered. The length to width ratio of the flap did not determine perfusion or oxygenation. Perfusion were preserved to a greater extent in the thick flaps (~40%) than in the thin flaps (~20%).On the other hand a full-thickness composite eyelid flap (paper V), which is an axial flap, there is only a slight decrease in perfusion. The results support the view that plastic surgery of the eyelids is permissive, and the rich vascularization of the eyelid due to the anastomotic network of vessels in the tarsal plate may increase the likelihood of flap survival and surgical success.In conclusion, modern techniques enables detailed flap monitoring and opens opportunities to optimize some surgical procedures.