Duration of corneal anaesthesia following multiple doses and two concentrations of tetracaine hydrochloride eyedrops on the normal equine cornea

Abstract

Duration of corneal anaesthesia following tetracaine instillation was established enabling a better use when performing diagnostic and therapeutic procedures. Comparison of tetracaine with other ocular anaesthetics needs to be published in the future.

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.…”

The effects of subconjunctival bupivacaine, lidocaine, and mepivacaine on corneal sensitivity in healthy horses

“…Pressure was increased until a small deflection was noted in the filament, and then the filament was removed from the cornea. This process was repeated up to five times for each length, and the filament length was decreased in 0.5‐cm increments until a blink response occurred in at least three of five stimulations . Following baseline CTT measurements in both eyes, each horse was sedated with xylazine (0.30–1.0 mg/kg intravenously) (X‐ject E Injection; Henry Schein ® Animal Health, Dublin, OH, USA).…”

“…These studies have found that the topical ophthalmic anesthetics used to provide analgesia for corneal procedures in horses have a short duration of action. [9][10][11][12] The duration of action of 0.5% proparacaine usually ranges from 25 to 35 min, while various formulations of tetracaine (0.5-1% aqueous or gel solutions) have been documented to last between 40 and 60 min in horses. 9,11,12 Local anesthetics that are not specifically formulated for topical ophthalmic administration, including 0.5% bupivacaine hydrochloride, 2% mepivacaine hydrochloride, and 2% lidocaine hydrochloride, have also been evaluated for their efficacy and duration of action when applied topically to the cornea.…”

Determination of tear break‐up time reference values and ocular tolerance of tetracaine hydrochloride eyedops in healthy horses

“…In a letter to editor, Koch and Rubin (1969) reported hyperaemia, chemosis and protrusion of the third eyelid after the instillation of tetracaine hydrochloride 0.5% (0.5% THCl) in 2 dogs. When comparing the results of 2 studies on corneal anaesthesia in horses, tetracaine seems to be more effective than proparacaine as it increases the chance of a maximal anaesthetic effect (Kalf et al 2008;Monclin et al 2008).…”