Anatomical features of the opening of the nasolacrimal duct and the lacrimal fold (Hasner's valve) for intranasal surgery: a cadaveric study.

The location and size of the opening of the nasolacrimal duct and the lacrimal fold (Hasner's valve) are variable. These features have clinical importance in nasal surgery because of the difficulty in determining their location. The aim of this study was to demonstrate the anatomical features of the opening of the nasolacrimal duct and the lacrimal fold and to discuss the importance of such knowledge in minimizing the risk of injury at surgery. Twenty sagittal head sections from formalin-fixed cadavers were examined. The sections showed no evidence of pathology or trauma. The type of opening of the nasolacrimal duct was a vertical sulcus in 14 of 20 (70%), an oblique sulcus in 2 of 20 (10%), an oblique fissure in 2 of 20 (10%), a vertical fissure in 1 of 20 (5%), and an anteroposterior fissure in 1 of 20 specimens (5%). The lacrimal fold was present in 16 of 20 specimens (80%). Five different forms of this fold were observed. Some morphological features were evaluated quantitatively. We believe that detailed anatomical knowledge of the opening of nasolacrimal duct will be useful in surgical approaches to this area.