Effects of artificial tear temperature on corneal sensation and subjective comfort

Purpose. Cooling reduces acute inflammation and local nerve sensation. We investigated the relationship between artificial tear temperature, ocular surface sensation, and patient comfort. Methods. We placed preservative-free artificial tears and eye mask stored at four temperatures (36°C, 25.2°C, 4°C, and -10°C) in the right eyes of 24 normal subjects, whose left eyes served as controls. Corneal and conjunctival sensations were measured and corneal temperature was recorded. Comfort was reported on a 7-point scale. Results. Corneal temperature was significantly lowered with all temperature artificial tears and frozen eye mask (p < 0.001 for each temperature relative to the previous one). Aesthesiometer readings were inversely correlated with corneal temperature (r = -0.45, p = 0.0005), decreasing with lower temperatures, reaching 2.0±1.3 g/mm² (p = 0.001) for the mask. Conjunctival sensation reacted similarly and was well correlated with both corneal temperature (r = 0.43, p = 0.0009) and corneal sensation (r = 0.39, p = 0.006). Treatments provided relief, with the 4°C tears being the most comfortable (p = 0.0001). Conclusion. Although there may still be some biases, cooled artificial tears provide relief to the eye by the mechanism of reduced corneal and conjunctival sensation.