RESUMEN
Purpose: To study the microsurgical anatomy of the lacrimal drainage system and to provide anatomical evidence for transnasal endoscopic lacrimal drainage system bypass surgery by autogenous tissue grafting. Materials and Methods: A total of 20 Chinese adult cadaveric heads in 10% formaldehyde, comprising 40 lacrimal ducts were used. The middle third section of the specimens were examined for the following features: the thickness of the lacrimal fossa at the anterior lacrimal crest, vertical middle line, and posterior lacrimal crest; the cross section of the upper opening, middle part, and lower opening of the nasolacrimal canal; the horizontal, 30° oblique, and 45° oblique distances from the lacrimal caruncle to the nasal cavity; the distance from the lacrimal caruncle to the upper opening of the nasolacrimal duct; and the included angle between the lacrimal caruncle–nasolacrimal duct upper opening junction and Aeby’s plane. Results: The middle third of the anterior lacrimal crest was significantly thicker than the vertical middle line and the posterior lacrimal crest (P > 0.05). The horizontal distance, 30° oblique distance, and 45° oblique distance from the lacrimal caruncle to the nasal cavity exhibited no significant differences (P > 0.05). The included angle between the lacrimal caruncle and the lateral wall middle point of the superior opening line of the nasolacrimal duct and Aeby’s plane was average (49.9° ± 1.8°). Conclusion: The creation of the bony tunnel should start from the middle or posterior middle part of the lacrimal fossa, extending toward the anterior inferior region with an optimal downward oblique angle of 45°.