The orientation of the lacrimal fossa to the bony nasolacrimal canal: An anatomical study

PURPOSE:: To examine the relative positions of the lacrimal fossa (LF) and the bony nasolacrimal canal (BNLC) in relation to each other and a reference plane. Methods:: Forty-two orbits and BNLCs from 21 Asian cadavers (9 men and 12 women; average age at death, 84.4 years; range, 70-99 years) had been fixed in 10% buffered formalin before use. After exposing the LF and the medial half of the BNLC, the authors measured the angles of the longitudinal axis of the LF and the BNLC relative to the aesthetic horizontal plane respectively. Based on these values, the relative orientation of the LF and the BNLC was determined and defined in terms of Δ BNLC-LF. A positive Δ BNLC-LF represents a nasolacrimal canal that descends posteriorly relative to the LF. Results:: The mean LF, BNLC, and Δ BNLC-LF were 9.5°, 19.8°, and 10.3°, respectively. In 39 passages (92.9%), the Δ BNLC-LF was positive, representing a nasolacrimal canal that is more posteriorly oriented than the LF. In 3 passages (7.1%), the Δ BNLC-LF was equal to or less than 0°; 2 of them (4.8%) had a straight course and 1 passage (2.4%) had a negative value. Conclusions:: In most patients, the BNLC is directed more posteriorly than the LF. This finding may help in preventing an inadvertent false passage during probing and intubation in patients with epiphora.