In Vivo Thickness of the Healthy Tympanic Membrane Determined by Optical Coherence Tomography.

ABSTRACT

OBJECTIVE: Tympanic membrane (TM) thickness is an important parameter for differentiation between a healthy and a pathologic TM. Furthermore, it is needed for modeling the middle ear function. Endoscopic optical coherence tomography (eOCT) provides the opportunity to measure the TM thickness of the entire TM in vivo. MATERIALS AND METHODS: A total of 27 healthy ears were examined by eOCT. The system uses a light source with a central wavelength of 1,300 nm. The endoscope with an outer diameter of 3.5 mm provides a field of view of 10 mm and a working distance of 10 mm. Thickness measurements were carried out at 8 points on the TM. Additionally, the existing literature was analyzed, and a mean TM thickness value was determined. RESULTS: The mean thickness of the TM over all measurement points of the pars tensa was 120.2 µm, and the pars flaccida was significantly thicker with a mean thickness of 177.9 µm. Beyond that, there were no significant differences between the single quadrants. The mean TM thickness in the literature was 88.8 µm. DISCUSSION: EOCT provides the possibility for in vivo thickness determination of the TM. The mean thickness seems to be higher than in the previous studies, which were mostly carried out ex vivo. Our study takes the three-dimensional refraction into account and provides a method for the refraction correction.