Corneal Sensitivity and Burning Sensation

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Abstract
Objectives: To compare the effect of topical 0.5% ketorolac tromethamine and 0.1% diclofenac sodium on human corneal sensitivity and to assess the intensity of burning sensation at specific intervals after drop instillation. Design and Setting: Double-masked parallel clinical study. Patients: Eleven women and 4 men (8 white, 4 Hispanic, 3 Asian), 22 to 60 years of age (mean[±SD], 34±10 years). Interventions: Repeated instillation of either ketorolac and placebo or diclofenac and placebo at 5-minute intervals. Main Outcome Measures: Assessment of corneal sensitivity before instillation, immediately after instillation, and after termination of drop application; and subjective evaluation of burning sensation by asking participants to rate burning on a scale ranging from 0 (none) to 3 (severe) after each drop application. Results: Both diclofenac (P<.01) and ketorolac (P<.01) decreased corneal sensitivity significantly, while the placebo had no measurable effect. After administration of additional drops over time, the effect of diclofenac and ketorolac increased. After termination of the drug instillation, corneal sensitivity returned to baseline significantly slower (P<.01) in participants receiving diclofenac than in those receiving ketorolac. Ketorolac (P=.01) and diclofenac (P<.05) were significantly more effective in whites than in nonwhites. Mean burning sensation was mild, and there was no statistically significant difference between the 2 drugs on this measure (P=.12). Conclusions: The decrease in corneal sensitivity in normal human corneas is more pronounced and longer lasting with diclofenac than with ketorolac. Both drugs are well tolerated topically and may be useful for pain reduction after refractive corneal surgery.