Identifying an appropriate animal model for the nasolacrimal drainage system.

PURPOSE: To determine a suitable animal model for further characterization of the nasolacrimal drainage system.
METHODS: A comprehensive Pubmed literature search was performed to locate articles pertaining to the histology or anatomy of the nasolacrimal drainage system in research animals. The histology of 2 nasolacrimal drainage systems of a cynomolgus monkey was also evaluated using hematoxylin-eosin stain.
RESULTS: Sixteen articles were identified that describe the anatomy and/or histology of the nasolacrimal drainage system in rabbits, rats, pigs, sheep, goats, horses, deer, llamas, camels, apes, dogs, and cats, with significant homology between these models. Notable exceptions were found in rat histology and rabbit anatomy. In the few experiments using animal models to investigate the nasolacrimal drainage system, the rabbit model was the most commonly used system. Light microscopy of the cynomolgus monkey nasolacrimal drainage system revealed markedly similar anatomy and histology to that of humans.
CONCLUSIONS: Literature review demonstrates a great deal of similarity in the anatomy and histology of the nasolacrimal drainage systems of 12 mammalian species. Although a common ophthalmic research animal, the rat model has significant histologic differences that prevent its use for comparison with the human lacrimal excretory system. Current literature suggests that despite anatomical variation, the rabbit animal model could potentially be used for further characterization of the nasolacrimal drainage system because it pertains to clinical applications in human patients. Preliminary light microscopy suggests that the cynomolgus monkey may be a superior model for nasolacrimal drainage research, but further studies are required.