Anatomical guidelines for intranasal surgery of the lacrimal drainage system.

To facilitate identification of the nasolacrimal duct during intranasal surgery, we have determined the distances between the lacrimal drainage system and certain anatomical structures on the lateral wall of the nasal cavity. A total of 15 adult cadaver skulls were bisected mid-sagittally and evaluated morphometrically. In our specimens, the average distance from the natural ostium of the maxillary sinus to the nasolacrimal duct (NLD) was only 5.5 mm. This rather small distance should be taken into consideration, in order to prevent trauma of the NLD during surgical enlargement of the ostium of the maxillary sinus. The distances from NLD to the anterior surface of the bulla ethmoidalis, the free edge of the uncinate process and the attachment point of the middle turbinate on the lateral nasal wall were found to be 10.2 mm, 8.8 mm and 5.4 mm, respectively. Taking these distances into account, easy identification of the NLD during endonasal dacryocystorhinostomy surgery will be possible.