Optical quality of the nasendoscope with and without the endosheath.

With the increasing use of the endosheath in clinical practice, we set out to investigate the quality of the nasendoscope image produced with and without an endosheath. It has been suggested by some users that the endosheath degrades the image. We used a spectrophotometer to assess the optical transmission of the endosheath and found no selective chromatic absorption. However, on requesting nine experienced users to document whether they could differentiate between the sheathed and unsheathed endoscope, a significantly correct answering pattern was obtained in repeated blinded experiments. This suggests that individuals can distinguish between the sheathed and unsheathed nasendoscope view and that the image is indeed altered when an endosheath is employed.