Operative settings and surgical techniques
The CO2 laser vaporization was performed under local anesthesia in the supine position as for the routine otomicroscopy ear surgeries. Ear speculum was fixed to expose the surgical field. The ear drum was cleaned and then painted with gentian violet to define the extent of epithelium defect. (Figure 2a) Then the gentian violent was cleared by cotton swab. CO2 laser was used to irradiate the lesion area. The machine of CO2 laser that we used was Lumenis 30c, setting 2 watts, continuous mode, with spot size of 0.5 mm (Figure 2b). We chose initial lower laser power setting to prevent penetrating injury of the ear drum. Repeat vaporization is allowed to make sure that epithelium layer has been irradiated. The extent of laser spot is same as previous stained area. In practice, one or two additional laser spot is often needed after evaluating the depth of first laser spot (Figure 2c). The TAA cauterization for patients in caustic agent group were also performed under local anesthesia by the same surgeon in supine position as for otomicroscopy ear surgeries. The preparation is same as that in laser group except that TAA (50%) was used to cauterize the epithelium defect. The TAA was applied to the lesion area by cotton tip and remove it after the lesion area was white out. The two strategies are all performed in the operation room.