In vitro efficacy of ocular surface lubricants against dehydration

To compare 3 ocular lubricants containing sodium hyaluronate (SH), carboxymethylcellulose (CMC), and hydroxypropyl methylcellulose (HPMC) for their ability to enhance water retention and to protect human corneal epithelial cells (HCECs) from dehydration.

Experiments were performed using 0.1% and 0.3% solutions of the 3 lubricants diluted in Milli-Q water for the water retention assays and in DMEM/F12 culture medium for the cell viability assays. Five milliliters of each of the lubricants was dropped onto a filter paper, and the paper was kept in an open container at 25°C and a humidity of 36% to 38%. The weight of the paper was measured hourly for 4 hours. In the second set of experiment, cultured HCECs were exposed to the test lubricants for 60 minutes, and the lubricants were removed. Cells were then exposed to room air for up to 60 minutes. Cells were then incubated with a vital dye, and the absorption of the reduced form of the dye was measured. The cell survival rate was compared for the 3 lubricants.

Filter papers moistened with both 0.1% and 0.3% SH were significantly heavier than those moistened with CMC and HPMC at all time points. The survival rate of HCECs was significantly higher at most times with 0.1% and 0.3% SH than with CMC and HPMC solutions. The effects of CMC were not significantly different from those of HPMC.

These findings indicate that SH is significantly better for water retention and protection of HCECs from dehydration than HPMC and CMC.