Abstract
Purpose :
To evaluate the effects of menthol-containing artificial tears on tear secretion, tear MUC5AC level, and tear LDH concentration in normal and an experimental rat model of dry eye.
Methods :
Total 32 male Lewis rats were used. After instillation of menthol-containing artificial tears (menthol, 0.64mM), tear secretion was separately measured using Zone Quick phenol red thread at 5, 10, and 15 minutes to determine the peak time of tear secretion. Tear stimulating effect of menthol-containing artificial tears was also evaluated after topical anesthesia with 0.5% proparacaine solution. Tear secretion, tear MUC5AC and LDH concentration were compared between menthol-containing artificial tears (menthol group) and vehicles (vehicle group) after single instillation to evaluate the immediate effect, and after repeated instillation (5 times a day for 5 days) to evaluate the longer-term effects. The effects of menthol-containing artificial tears were also evaluated in an experimental rat model of dry eye.
Results :
The increase of tear secretion peaked at 5 minutes after instillation of menthol-containing artificial tears (8.2mm). However, after topical anesthesia, tear secretion was not significantly different with baseline measurement. Tear secretion increased from 4.37(±0.75) at baseline to 7.37 (±1.60) after single instillation of menthol-containing artificial tears. However, after repeated instillation for 5 days, the effects of tear stimulation decreased. Tear MUC5AC concentration was significantly lower in menthol group than vehicle group after single instillation, not after repeated instillation. However, tear LDH concentration was significantly increased in menthol group after repeated instillation for 5 days. In the experimental rat model of dry eye, the menthol effect of tear stimulation was reduced.
Conclusions :
Menthol-containing artificial tears increased tear secretion, but lowered tear MUC5AC concentration. However, the tear stimulation effects of menthol component were reduced after repeated instillation for 5 days and in the experimental rat model of dry eye. Menthol-containing artificial tears seem to be less effective in dry eye treatment.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.