Acute Corneal Toxicity of Combined Antiglaucoma Topical Eyedrops

To investigate the corneal toxicity of three combined antiglaucoma topical eyedrops using transepithelial electrical resistance (TER) and scanning electron microscopy (SEM).

Corneal TER changes after a 60-s exposure to latanoprost/timolol with 0.02% benzalkonium chloride (BAC), travoprost/timolol with polyquaternium-1, and dorzolamide/timolol with 0.005% BAC were measured in living rabbits. Corneal damage was also examined by SEM. Hank's balanced salt solution (HBSS) was used as a control.

There was a significant decrease in the corneal TER after exposure of the cornea to latanoprost/timolol with 0.02% BAC. Travoprost/timolol with polyquaternium-1 and dorzolamide/timolol with 0.005% BAC did not produce any significant decrease in the corneal TER as compared to HBSS control eyes. SEM revealed that superficial cells of corneas treated with latanoprost/timolol with 0.02% BAC were damaged and exhibited degenerated microvilli. Conversely, the superficial cells of corneas exposed to travoprost/timolol with polyquaternium-1 or dorzolamide/timolol with 0.005% BAC appeared normal and had normal microvilli under SEM examinations.

The corneal toxicity of latanoprost/timolol with 0.02% BAC is greater than that of travoprost/timolol with polyquaternium-1 and dorzolamide/timolol with 0.005% BAC. Latanoprost/timolol contains 0.02% BAC, which may be responsible for the corneal toxicity.