Evaluation of corneal anaesthesia after the application of topical 2 per cent lidocaine, 0.5 per cent bupivacaine and 1 per cent ropivacaine in dogs

Abstract

The objective of this study was to describe and compare the efficacy and duration of topical anaesthesia induced by 2 per cent lidocaine (L), 0.5 per cent bupivacaine (B) and 1 per cent ropivacaine (R) in the dog using 24 clinically healthy beagles with normal ocular examination. Dogs were randomly divided into three groups: 2 per cent lidocaine (n=8), 0.5 per cent bupivacaine (n=8) and 1 per cent ropivacaine (n=8). The baseline corneal touch threshold (CTT) was measured using a Cochet-Bonnet aesthesiometer. Following baseline CTT measurement, a single drop of the assigned anaesthetic was applied to each eye and the CTT was measured bilaterally within one minute after administration and every five minutes until the basal CTT value was restored. Data were analysed with non-parametric analysis of variance models and Dunnet's test for post hoc analysis. One per cent ropivacaine was the most effective drug (LCTTmax=3 cm, BCTTmax=2 cm, RCTTmax=0 cm; P<0.001), and had the shortest latency (LLatency=5 minutes, BLatency=5 minutes, RLatency=1 minute; P<0.001) and the smallest AUC (LAUC=80 cm×minute, BAUC=68.25 cm×minute, RAUC=36.88 cm×minute; P<0.001). There was no statistical difference in the duration of corneal anaesthesia between the groups (P=0.09) and all topical anaesthetics tested reduced corneal sensitivity, although 1 per cent ropivacaine had the maximal and quickest anaesthetic effect. This drug could be used for specific diagnostic procedures where quick and short, but effective, corneal anaesthesia is needed.

The effects of topical diclofenac, topical flurbiprofen, and humidity on corneal sensitivity in normal dogs

“…) supports those conclusions, and it is recommended that environmental conditions be reported when evaluating corneal sensitivity in an effort to standardize data. For example, in a study of dogs from Barcelona, Spain baseline corneal sensitivity was reported as 40 mm while a similar study in Toulouse, France reported a baseline of 15 mm. Both locations are similar in latitude and longitude, but vastly different weather conditions may exist during similar parts of the year.…”

“…For instance, the lowest humidity in Barcelona occurs during February, while in Toulouse, this occurs during the end of July . The authors of the Barcelona and Toulouse studies confirmed the timeframe in which the experiments were performed. Interestingly, the Toulouse study was performed during higher humidity conditions, which may explain the vast difference in corneal sensitivity values reported compared to those obtained in Barcelona.…”

“…Between those studies, the difference in environmental humidity was 10–15%, which is further exacerbated when outside cold air is carried indoors and heated, thus resulting in a further decrease in humidity. When data from the current study is extrapolated, both the Barcelona and Toulouse studies follow the inversely proportional relationship between humidity and Cochet‐Bonnet esthesiometry measurements with lower corneal sensitivity values obtained in higher humidity.…”

Effects of topical application of 0.4% oxybuprocaine hydrochloride ophthalmic solution and 1% ropivacaine hydrochloride on corneal sensitivity in rats

“…The sample size was deduced from previous similar studies, which showed a rather heterogeneous sampling size: i.e. 8 [beagles, [17]], 9-10 [rats, dogs, [16]], 12+12 [cows, [11]], 12-22 [dogs, [5]], 18 [cats, [9]], 20 [cats, [18]]. In addition, this sample size resulted in an attempt to conform with the guiding principles for the ethical use of animals in testing ("The Three Rs").…”

“…Most of these research studies assessed the effectiveness of ropivacaine for peribulbar anesthesia and as a topical agent in cataract surgery. Few studies have investigated its effect on corneal sensitivity [17,31], and, to the author's knowledge, no similar study was performed out in rats.…”