Drainage of tears: impact on the ocular surface and lacrimal system.

The human efferent tear ducts are part of the lacrimal system. Because little knowledge exists concerning the physiology of the nasolacrimal system, and hence its patho- physiology, the nasolacrimal system has received almost no consideration as a possible factor in dry eye. The human nasolacrimal ducts consist of the upper and the lower lacrimal canaliculus, the lacrimal sac, and the nasolacrimal duct.

The cavernous body of the human efferent tear ducts contributes to regulation of tear outflow.

Purpose: To test the hypothesis that the surrounding vascular plexus of the lacrimal sac and the nasolacrimal duct contributes to the regulation of tear outflow.

Methods: Experiments in 30 probands aged between 15 and 37 years were performed in both nasolacrimal systems of each subject by observing with an endoscope the transit time of an applied tear drop containing fluorescein dye until its entry into the inferior meatus of the nose. Four different experiments were performed to determine the median transit time under normal conditions and the influence on transit time of a decongestant drug, a foreign body on the ocular surface, and a decongestant drug applied together with a foreign body on the ocular surface.

Characterization of mucins in human lacrimal sac and nasolacrimal duct.

Purpose: Mucins are polymers that may reduce drag and enhance tear outflow. Mucin expression and distribution in human efferent tear ducts were tested in the physiological state, and potential differences in the expression pattern were investigated in the presence of primary acquired dacryostenosis (PANDO).

Methods: Expression of mucins in human lacrimal sac and nasolacrimal ducts was monitored by reverse transcription-polymerase chain reaction analysis.

Loss of tear duct-associated lymphoid tissue in association with the scarring of symptomatic dacryostenosis.

Objective: To determine whether organized mucosa-associated lymphoid tissue (MALT) is a normal component of the human efferent tear ducts or is acquired in reaction to chronic inflammation.

Design: Nonrandomized comparative (cadaver controlled) study with histopathologic correlations.

Materials: Tissue specimens from nasolacrimal ducts of 38 patients undergoing endonasal dacryocystorhinostomy in postinflammatory dacryostenosis with signs of chronic inflammation were analyzed using histologic examination and immunohistochemical studies.

TFF peptides in the human efferent tear ducts.

Purpose: To determine whether the lining epithelium of the human lacrimal sac and nasolacrimal duct synthesizes TFF peptides (formerly P-domain peptides, trefoil factors), a family of mucin-associated secretory peptides.

Methods: Expression of TFF peptides in human lacrimal sac and nasolacrimal ducts was monitored by reverse transcription-polymerase chain reaction and Western blot analysis. Antisera specific for TFF peptides were used in immunohistochemical analysis to determine the presence and distribution of all three TFF peptides in epithelia of the lacrimal passage.

Animal model for the absorption of lipophilic substances from tear fluid by the epithelium of the nasolacrimal ducts.

Purpose: To compare the nasolacrimal tissues of several species to see how closely they resemble the human and to measure nasolacrimal absorption of a substance, to show that an absorption pathway exists for substances placed in the external eye, other than directly through the cornea or conjunctiva.

Methods: The nasolacrimal systems of six different vertebrates were investigated by light microscopy to find a species with a nasolacrimal system comparable to that of humans, for use in absorption experiments. In addition to primates, rabbits were revealed by histology to have a lacrimal system closely comparable to that of humans.