Evaluation of duration of corneal anesthesia induced with ophthalmic 0.5% proparacaine hydrochloride by use of a Cochet-Bonnet aesthesiometer in clinically normal horses

Abstract

Duration of corneal anesthesia in horses was shorter than in dogs, and degree of maximal effect was less than in cats and dogs, most likely because of increased sensitivity of the equine cornea, compared with corneal sensitivity in those species.

Comparison of efficacy and duration of effect on corneal sensitivity among anesthetic agents following ocular administration in clinically normal horses

“…The mean baseline corneal sensitivity (determined via CTT measurement) did not vary significantly among drug solution treatments within a given experimental group (the completely randomized design experimental group or the replicated Latin square experimental group); baseline CTT values ranged from 2.9 to 3.9 cm, which is in accordance with results of previous studies [7][8][9][10]22 in horses that were evaluated by use of the same type of aesthesiometer. After treatment administration, CTT values differed significantly from the respective baseline value for some time, depending on drug solution; among the drug solutions, significant differences in CTT values were detected at various time points after application.…”

“…6 The CTT has been studied as a measure of corneal sensitivity in horses of various ages and breeds, and its mean value has been reported to range from 2.12 ± 0.62 cm to 5.01 ± 0.61 cm as determined by use of the Cochet-Bonnet corneal aesthesiometer. [7][8][9][10] Previous studies 7,9 in horses have revealed that the central portion of cornea is the most sensitive, followed in order of decreasing sensitivity by the nasal, temporal, ventral, and dorsal regions. It is presumed that these location-related differences in corneal sensitivity reflect the relative abundance in nerve fiber density at these locations because the central portion of the cornea in other animals has the greatest corneal nerve fiber density.…”

“…This drug formulation has a rapid onset of action (< 5 minutes in most species) with a variable duration of effect (durations of 25 minutes in horses and cats and 45 minutes in dogs). 8,15,16 The manufacturer recommends keeping the solution refrigerated when not in use, and the drug' s efficacy decreases if the solution is not maintained accordingly. 17 The storage requirement for proparacaine ophthalmic solution is difficult to maintain in certain clinical situations and when traveling to evaluate patients in the field.…”

Ophthalmic and anesthetic evaluation of topical 1% tetracaine and 0.5% proparacaine in dogs

“…In studies with other species, the average duration of proparacaine was 10 minutes (Bartfield et al, 1994) and 11 minutes (Weiss end Goren, 1991) in humans, 10 minutes in rabbits (Seabaugh et al, 1993), 25 minutes in cats (Binder and Herring, 2006) and 25 minutes in horses (Kalf et al, 2008).…”

“…Vet. Zootec., v.63, n.6, p.1337-1344, 2011 2005), cats (Binder and Herring, 2006), rabbits (Seabaugh et al, 1993), horses (Kalf et al, 2008) and men (Ezra and Allan, 2007).…”