(154b) Transport of Water and Ions across the Cunjunctiva and Its Effect on Ocular Tear Dynamics

In this talk we will describe a model for transport of water and ions across the conjuctival membrane in the eyes, and couple the conjunctival transport with tear drainage and evaporation to develop a comprehensive model for tear dynamics.

The conjunctiva transport model includes transport through Cl channels and Na-Glucose cotransporters at the apical (tear) side, and the Na-K pump, Na-K-Cl cotransporters and K channels at the basolateral (systemic circulation)side. In addition to the conjunctiva transport, the tear dynamics model includes flow of fluid through the canaliculi.

The tear dynamics model predicts that under physiological conditions the tear volume, tear osmolarity and potential are 7.1 µm, 297.6 mM and -15.1 mV, respectively. The model also predicts that the conjunctiva is secretory under normal condition and contributes about 25% of the total tear production. We also predict the effect of evaporation on tear physiology and show that increase in evaporation increases osmolarity, reduces tear volume and increase conjuctival secretion. Additionally, the new tear dynamics model helps assess the effect of instilling solution with different osmolarities, insertion of punctal plug and use of moisture chamber as treatments for dry eyes. Furthermore, the model is used to predict the effect of modulation of specific transport pathways, which is proposed as a potential remedy for dry eyes, on conjuctival secretion and total tear volume.