Purpose: This study was designed to examine the anatomical relationship between Horner's muscle and the lacrimal sac at 3 representative levels of the lacrimal sac and to verify the contribution of Horner's muscle to lacrimal sac drainage.
Methods: Seven ocular specimens from 7 elderly Japanese cadavers, fixed in 10% buffered formalin, were analyzed. Axial sections were made parallel to the eyelid margin at 1 mm above the upper eyelid margin, 1 mm below the lower eyelid margin, and 3 mm below the lower eyelid margin. The vertical common fascial length, length of the lateral lacrimal sac wall, and the proportion between the 2 were measured for each specimen at the 3 levels.
Results: The vertical common fascial length and its proportion to the length of the lateral lacrimal sac wall were statistically the same at all 3 levels of the lacrimal sac.
Conclusions: Based on the present anatomical findings, the activity of Horner's muscle may be the same for all sac levels, although this hypothesis should be examined by further experimental research, such as manometric studies of the sac at different levels along its length.