Purpose: The aim of this study was to investigate the effect of lubricant eyedrops containing propylene glycol 400 (PEG) and polyethylene glycol (PG) with hydroxypropyl guar (HP-guar) as a gelling agent on the precorneal mucous layer in vivo.
Methods: Sixteen New Zealand white rabbits were randomly assigned to 1 of 4 groups. All rabbits received PEG/PG/HP-guar tear products in the right eye. PEG/PG/HP-guar with Polyquad, 0.1% hyaluronate sodium, 0.5% carboxymethylcellulose, or phosphate-buffered saline was placed in the left eyes of animals in each group. All eyedrops were used 4 times a day for 7 days. An additional 8 rabbits were randomly assigned to 1 of 2 groups. One group received PEG/PG/HP-guar products 4 times a day for 7 days (long-term exposure group), and the other group received PEG/PG/HP-guar products 3 times at 5-minute intervals (short-term exposure group). Fifteen minutes after the last drop was administered, each cornea was immediately excised and mucous layer thickness measured by transmission electron microscopy.
Results: Mucous layer thickness was significantly greater in eyes treated with PEG/PG/HP-guar products compared with those treated with 0.1% hyaluronate sodium, 0.5% carboxymethylcellulose, or phosphate-buffered saline (all P values < 0.001). There were no significant differences in mucous layer thickness between PEG/PG/HP-guar products and PEG/PG/HP-guar with Polyquad or in the long- and short-term exposure animals.
Conclusions: This study demonstrates that even a short exposure to PEG/PG/HP-guar tear product increased precorneal mucous layer thickness.