Corneal damage and its recovery after instillation of preservative-free versus preserved latanoprost eye drops.

Latanoprost ophthalmic solution is highly effective as a therapeutic agent for glaucoma and is applied worldwide. However, harmful effects on the corneal surface have been reported regarding the commercially available latanoprost ophthalmic solution. Corneal surface toxicity may be caused by the added preservative of the ophthalmic solution. In order to ascertain whether latanoprost itself can damage the cornea or if this is solely due to the added preservatives, this study attempted to determine the corneal changes that occur at different time periods following usage of preservative-free versus preserved latanoprost eye drops. Preservative-free latanoprost eye drops (Monoprost) or preserved latanoprost eye drops (Xalatan) containing 0.02% benzalkonium chloride (BAC) were instilled in the corneas of rabbits. For each of the two different eye drop solutions, the rabbits used in this experiment were divided into three exposure groups: 1 minute, 24 hour, and 1 week groups. Corneal transepithelial electrical resistance (TER) and scanning electron microscopy (SEM) were examined immediately (1 minute) after instillation, at 24 hours after instillation, and at 24 hours after 1 week of daily instillations of latanoprost. Hank's balanced salt solution was used in the control group. The mean corneal TER of the control group was 933.8 ± 279.0 Ω cm. In preservative-free latanoprost instilled corneas, there was no significant decrease in the TER or morphological changes at any of the time points, with the relative TER values of 117 ± 38%, 100 ± 34%, and 93 ± 21% for 1 minute, 1 day, and 1 week time points, respectively. In preserved latanoprost instilled corneas, SEM showed that only the immediate group exhibited superficial cell damage and a significant decrease in the corneal TER compared to the controls and other time points and to the immediate preservative-free latanoprost corneas. In the preserved latanoprost groups, the relative TER values were 18 ± 5%, 110 ± 28%, and 92 ± 10%, for the three respective observation time points. Preservative-free latanoprost can be safely instilled to the corneal epithelium. Latanoprost with 0.02% BAC has an immediate deleterious impact on the corneal epithelium; however, it disappears within 24 hours after instillation.