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.