Effects of topical application of tramadol with/without dexmedetomidine and proparacaine on corneal sensitivity in rats

To evaluate the corneal anesthetic effect following topical application of tramadol alone and in combination with dexmedetomidine, and compare it to proparacaine, in clinically healthy rats. A randomized, crossover study was performed. Twenty Wistar albino rats (n = 40 eyes) were used. Corneal touch threshold (CTT) measurements (in mm) were obtained using a Cochet-Bonnet aesthesiometer. CTT measurements were obtained at baseline, 1-min following application of the topical anesthetic agent, and repeated at 5-min intervals up to 75 min. The topical protocol involved 3 treatment conditions, separated by a 2-week washout period: proparacaine, tramadol alone, and tramadol in combination with dexmedetomidine. CTT values were significantly decreased compared to baseline at each timepoint until completion of the 75-min evaluation in all treated eyes, regardless of the assigned treatment (p