Effect of topical application of 2% lidocaine gel on corneal sensitivity of clinically normal equine eyes

Abstract Objective To assess the degree and duration of corneal anaesthesia provided by topical application of a non-ophthalmic 2% lidocaine gel in horses. Study design Experimental, ‘blinded’, randomized prospective study. Animals Twelve adult horses without relevant ocular abnormalities. Methods Baseline corneal touch threshold (CTT) measurements were obtained bilaterally by use of a Cochet–Bonnet aesthesiometer just prior to topical treatment. A volume of 0.2 mL of 2% lidocaine gel was administered in one randomly selected eye and the same volume of a viscous lubricant in the other eye to serve as control. The CTT value was measured on both eyes 5, 10, 20, 30, 45, 60, 75 and 90 minutes after drug application. The potential for local adverse effects following lidocaine gel application was also evaluated. Results Mean CTT baseline measurements were not significantly different ( p  > 0.05) between the control eyes (3.41 ± 0.56 cm) and those subsequently treated with the lidocaine gel (3.50 ± 0.64 cm). In control eyes, no significant changes in corneal sensitivity ( p  > 0.05) occurred over time during the study period. By contrast, a marked reduction in corneal sensitivity was observed after lidocaine application, with mean CTT values significantly lower ( p Conclusions and clinical relevance Deep and sustained corneal anaesthesia is achieved after application of 2% lidocaine gel to the equine eye, with minimal changes in the corneal epithelium. It might be useful for minor ophthalmic surgeries performed in the standing sedated horse.