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Topical NSAIDs similarly affect corneal sensitivity
Diclofenac provided the greatest decrease in corneal sensitivity, while nepafenac provided the smallest decrease.
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All four currently available ocular topical NSAIDs — generic diclofenac, generic ketorolac, brand bromfenac and brand nepafenac — showed anesthetic effects similar to brand diclofenac and brand ketorolac, according to a study.
“The study demonstrated that the two currently used NSAID brands have anesthetic characteristics similar to the two original NSAIDs. It had long been assumed but never confirmed,” John R. Wittpenn, MD, the corresponding author, told Ocular Surgery News. “Diclofenac continues to have the greatest anesthetic effect. The reason is not known.”
Patients and methods
The study, published in Cornea, included 10 healthy adult volunteers who underwent corneal sensitivity testing and received topical NSAIDs.
John R. Wittpenn
An esthesiometer was used to measure baseline corneal sensitivity. The instrument comprises nylon filaments of 0.1 mm in diameter and 60 mm in length. Longer lengths of exposed filaments corresponded to less pressure applied to the cornea. The filament was directed toward each subject’s right eye until it touched the cornea, as shown by slit lamp examination.
Each patient was randomized to receive one of four topical NSAIDs: generic 0.1% diclofenac sodium ophthalmic solution, generic 0.5% ketorolac tromethamine ophthalmic solution, brand 0.3% nepafenac ophthalmic suspension (Ilevro, Alcon) or brand 0.07% bromfenac ophthalmic solution (Prolensa, Bausch + Lomb).
One drop of each agent was applied to the right eye every 5 minutes, for a total of four drops. After the last drop was instilled, investigators measured corneal sensitivity every 15 minutes for 1 hour.
After 1-week washout periods, subjects were re-randomized to receive one of the three other topical agents until they received all four agents. Corneal sensitivity measurements were repeated each week.
Results and findings
All four topical NSAIDs had similar corneal sensitivity profiles over time.
Corneal sensitivity decreased significantly from baseline after topical application, remained flat from 0 to 30 minutes and then reverted to baseline from 45 to 60 minutes (P < .001) in all groups.
Time to return to near baseline corneal sensitivity was similar for all four NSAIDs.
The maximum absolute decrease in corneal sensitivity was 28.6 mm for diclofenac, 21.1 mm for ketorolac, 16.9 mm for bromfenac and 16.4 mm for nepafenac. The difference in the maximum decrease in sensitivity was significant only between diclofenac and nepafenac.
No adverse reactions to topical NSAIDs were reported.
Mechanisms of action
Wittpenn described mechanisms of action that may explain the anesthetic and analgesic effects of topical NSAIDs.
“The analgesic effect is due to prostaglandin inhibition. The anesthetic effect is thought to be direct blockage of nerve fibers, but this is not known,” Wittpenn said.
In addition, the currently used NSAIDs slow wound healing despite having anesthetic qualities, he said.
“They definitely slow wound healing, especially if they are used at frequent dosing of greater than [four times a day],” he said.
It is not certain whether NSAIDs affect ocular surface diseases such as dry eye syndrome.
“It is unknown regarding the treatment of dry eye. They may help symptoms but not tear osmolality,” Wittpenn said.
The study authors said that a decrease in corneal sensitivity may increase the likelihood that a patient will touch his or her eye and cause further trauma or infection. – by Matt Hasson
Reference:
Singer DD, et al. Cornea. 2015;doi:10.1097/ICO.0000000000000309.For more information:
John R. Wittpenn, MD, can be reached at Ophthalmic Consultants of Long Island, 4 Technology Drive, East Setauket, NY 11733; email: jwittpenn@ocli.net.Disclosure: Wittpenn reports no relevant financial disclosures.