Effects of antiglaucoma drugs on the ocular surface in rabbits: a fixed-combination drug versus two concomitant drugs

We investigated the effects of a fixed-combination antiglaucoma drug and compared it with two concomitant antiglaucoma drugs on the ocular surface. Twenty-four rabbits were randomized into four groups. Group 1 was administered timolol, group 2 travoprost, group 3 a travoprost/timolol fixed-combination solution, and group 4 timolol and travoprost. Conjunctival impression cytology specimens were collected at baseline and weeks 1, 3, and 6, and conjunctival biopsy specimens at week 6. The impression cytology study results were as follows: No statistically significant differences among group 1-3 at any time (p > 0.05); a statistically significant difference between groups 3 and 4 at week 6 (p = 0.003); a statistically significant difference between baseline and group 4 at week 6 (p = 0.008). Conjunctival biopsy specimens of group 1-3 showed no distortion of the conjunctival epithelial structures, but group 4 showed decreased layers of epithelial cells with fewer periodic acid-Schiff (PAS) (+) goblet cells. A fixed-combination antiglaucoma drug is beneficial in reducing adverse ocular surface changes in long-term use. This is believed to be due to the smaller concentration of preservatives contained in the fixed-combination drug.