Meet the Lacrimal Sac: Endoscopic Surgeons' Road Map.

Knowledge of lateral nasal wall landmarks in relation to lacrimal apparatus is essential for successful endoscopic dacryocystorhinostomy. This descriptive study of right and left sagittally sectioned ten adult cadaver head specimens was done measuring various lateral nasal wall anatomical landmarks including lacrimal apparatus with digital calipers. Maxillary line was identified in 75%, majority overlapping lacrimal sac. Genu of middle turbinate was at or posterior to nasolacrimal duct. Mean distance of superior end of sac was 8.88 mm above axilla, between its anterior edge and axilla was 10.58 mm and its length was 11.72 mm. Considering above measurements, 'Rule of 10' can be applied for nasal mucosal incision. A "Three Tier Approach" to overcome mucosal (nasal), bony (lacrimal and frontal process of maxilla) and mucosal (sac) boundaries exposes lacrimal sac up to its inferior limit ensuring successful endonasal endoscopic dacryocystorhinostomy.