Scanning Electron Microscopic Features of the External and Internal Surfaces of Normal Adult Lacrimal Drainage System

The aim of this study was to examine the ultrastructural features of the external and internal surfaces of healthy lacrimal drainage systems.

A prospective interventional study was performed on the healthy adult lacrimal drainage systems obtained from fresh exenterated specimens. Exenteration was performed for malignancies unrelated to lacrimal system where preoperative lacrimal evaluation was normal. A careful and thorough dissection was carried out to isolate the entire lacrimal drainage system from the punctum to the nasolacrimal duct. The analysis was performed using the standard protocols of scanning electron microscopy.

Inner punctal surfaces showed a definite and slightly elevated junction between the luminal surfaces of punctum and beginning of the vertical canaliculus. Similar junction could be identified between the lacrimal sac and nasolacrimal duct. The valves of the canaliculi showed broad rugae-like mucosal surfaces, whereas the external surfaces of the canaliculi demonstrated well-defined orbicularis muscle with collagenous attachments. The walls of the lacrimal sac and nasolacrimal duct showed dense vascular plexus which included wide luminal arteries, throttle veins, and large capacitance vessels.

Ultrastructural features of external and internal surfaces of lacrimal drainage system help in better understanding of its anatomy and physiology. The junctional area between the punctum-vertical canaliculus and lacrimal sac-nasolacrimal duct needs further exploration to understand their roles.