Corneal anesthetic effect and ocular tolerance of 3.5% lidocaine gel in comparison with 0.5% aqueous proparacaine and 0.5% viscous tetracaine in normal canines

Investigation of fluorescein stain-based tear film breakup time test reliability in dogs in a clinical setting

OBJECTIVE

To determine intra- and interobserver reliability of a fluorescein stain-based tear film breakup time (TFBUT) test as performed in a clinical environment with and without administration of a topical anesthetic.

ANIMALS

21 privately owned dogs.

PROCEDURES

A randomized study design was used. Two independent observers that commonly perform the TFBUT test in clinical practice read the same description of TFBUT. Observers performed TFBUT testing for each dog before and after topical administration of 0.5% proparacaine solution in 4 testing periods with a 1-hour interval between periods. Intraclass correlation coefficient (ICC) analysis was used to assess inter- and intraobserver test reliability. Linear mixed models were used to assess the main effects of testing period, observer, eye, and presence of ophthalmic disorders and their interactions on TFBUT.

RESULTS

Mean TFBUT measurements performed by observer 1 and observer 2 were 5.9 seconds and 8.6 seconds, respectively, when adjusted for other effects in the model. Intraobserver ICC was poor for one observer and moderate for the other. Interobserver ICC was poor without use of topical anesthetic and slightly lower when anesthetic was used. Observer and testing period were each significantly associated with TFBUT; the measurements decreased and were more variable after multiple applications of fluorescein stain and proparacaine.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested tear film stability is negatively affected by topical administration of 0.5% proparacaine solution and repeated applications of fluorescein stain. The TFBUT test as performed in this study had poor to moderate reliability.

Evaluation of corneal anaesthesia after the application of topical 0.5% bupivacaine, 2% lidocaine and 0.4% oxybuprocaine in normal horses

OBJECTIVE

To compare the corneal anaesthetic effect of 0.5% bupivacaine, 2% lidocaine and 0.4% oxybuprocaine on normal equine eyes.

STUDY DESIGN

Prospective, blinded crossover study.

ANIMALS

A group of 10 clinically healthy horses.

METHODS

Corneal sensitivity was determined in each eye by measuring corneal touch threshold (CTT). The study had three phases. Each subject was randomly given one of the three treatments followed by a 72 hour washout period. Every horse received all treatments. Baseline CTT was recorded prior to anaesthetic instillation (T0) then CTT was measured 5 and 10 minutes after (T1 and T2, respectively), then 20 to 90 minutes (T3 to T10) at 10 minute intervals. CTT data were compared among treatments at each time point using the Friedman test p < 0.05.

RESULTS

Median (range) baseline CTT was 51.3 (25.0-60.0) mm for bupivacaine, 50.0 (40.0-55.0) mm for oxybuprocaine and 55.0 (30.0-60.0) mm for lidocaine. All treatments caused a significant decrease in CTT at T1. The lowest CTT was observed at T3 with bupivacaine and oxybuprocaine treatments. Median CTTs at this time point were 18.7 (5.0-25.0) mm and 28.7 (25.0-40.0) mm, respectively. The lowest CTT with lidocaine treatment was 28.7 (20.0-50.0) mm at T6 (50 minutes). At T3, CTT was significantly lower with the bupivacaine treatment compared with oxybuprocaine and lidocaine treatments (p < 0.0074). There was no significant difference in CTT values between T1 and T6 for bupivacaine, between T1 and T7 for lidocaine, and between T1 and T8 for oxybuprocaine. Duration of the maximum effect was 45 minutes for the bupivacaine, 55 minutes for the lidocaine and 65 minutes for the oxybuprocaine treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of a 0.5% injectable solution of bupivacaine or a 2% lidocaine had similar anaesthetic effect to the commonly used oxybuprocaine. Therefore, they might be used as alternatives for corneal anaesthesia.

Comparison of the use of a standard cytology brush versus a mini cytology brush to obtain conjunctival samples for cytologic examination in healthy dogs

OBJECTIVE

To compare the quality of conjunctival samples for cytologic examination obtained with 2 conjunctival exfoliative brushes, a mini cytology brush (MCB) and a standard cytology brush (SCB), in healthy dogs.

ANIMALS

20 client-owned dogs that were free of ocular disease.

PROCEDURES

A prospective single-center randomized trial was performed. For each dog, conjunctival samples of the right eye were obtained with the 2 brushes (ie, SCB or MCB) at 2 time points that were 5 to 11 days apart. The left eye was used as a control. Cytologic quality of conjunctival samples was scored on the basis of cellularity, clearness of background, uniformity of distribution of cells on the cytology slide, artifacts, cellular overlapping, cell preservation, presence of mucus on the cytology slide, and number of RBCs.

RESULTS

On cytologic evaluation, conjunctival samples collected with an SCB scored significantly better in terms of higher cellularity, less background debris, and more uniformity in the distribution of cells, compared with conjunctival samples collected with an MCB. Conjunctival samples collected with an MCB scored significantly better in terms of less cellular overlapping and less mucus in the background, compared with conjunctival samples collected with an SCB.

CONCLUSIONS AND CLINICAL RELEVANCE

Overall conjunctival samples obtained with an SCB for cytologic evaluation had better diagnostic quality, compared with conjunctival samples obtained with an MCB. Use of an MCB, however, was advantageous to access localized conjunctival areas as well as collect conjunctival samples from patients with small palpebral fissures.

Corneal anesthesia associated with topical application of 2% lidocaine nonophthalmic gel to healthy canine eyes

OBJECTIVE

To assess the degree and duration of corneal anesthesia induced by topical application of 2% lidocaine gel to the healthy canine eye.

ANIMALS

Nineteen adult Beagles free of ocular abnormalities.

PROCEDURES

Baseline corneal touch threshold (CTT) was measured bilaterally with a Cochet-Bonnet aesthesiometer. The 2% lidocaine gel (0.1 mL) was applied to one eye, randomly assigned, and the same volume of a lubricant gel was applied to the opposite eye. The CTT measurements were repeated bilaterally within 1 minute, after drug application, and every 5 minutes, until the baseline corneal sensitivity was restored. The potential for local adverse effects was evaluated.

RESULTS

Complete desensitization of the cornea (CTT = 0) was achieved one minute after lidocaine gel application and was maintained during 25.3 ± 12.5 minutes. Overall, the corneal sensitivity was significantly decreased for 58.4 ± 16.6 minutes compared with baseline level. Minor and reversible punctate epithelial erosions of the cornea were observed in the two treatment groups and were attributed to the anesthetic effect and the aesthesiometry procedure.

CONCLUSIONS

In the current study, the 2% lidocaine gel provided a sustained, deep and well-tolerated corneal anesthesia in ophthalmically normal dogs.

Effects of topical flurbiprofen sodium, diclofenac sodium, ketorolac tromethamine and benzalkonium chloride on corneal sensitivity in normal dogs

To evaluate corneal sensitivity by using the Cochet-Bonnet® esthesiometer in normal canine eyes at different time points following instillation of three different topical non-steroidal anti-inflammatory drugs (flurbiprofen sodium 0.03%, diclofenac sodium 0.1% and ketorolac tromethamine 0.5%) and benzalkonium chloride 0.01%. Six healthy mixed breed dogs from the same litter were used in two different stages. First, one drop of flurbiprofen sodium 0.03% and diclofenac sodium 0.1% in each eye; second, one drop of ketorolac tromethamine 0.5% and benzalkonium chloride 0.01% in each eye. Baseline esthesiometry was obtained before eye drop application and every 15 minutes thereafter until a total of 105 minutes of evaluation time. A one-week interval was allowed between the two treatment phases. Statistical analysis was used to compare means according to time of evaluation and drug used. Diclofenac sodium 0.1% decreased corneal sensitivity at 75 and 90 minutes (P > 0.015) with possible interference on neuronal nociceptive activity and analgesic effect while ketorolac tromethamine 0.5% did not show any variation for esthesiometry means along the evaluation. Flurbiprofen sodium 0.03% resulted in increased esthesiometry values 30 minutes after instillation (P > 0.013), increasing corneal sensitivity and possibly producing a greater irritant corneal effect over its analgesic properties. Benzalkonium chloride 0.01% significantly increased corneal sensitivity at 15 minutes of evaluation (P > 0.001), most likely resulting from its irritating effect. Esthesiometry did not allow a definite conclusion over the analgesic effect of the NSAIDs tested; however it was effective in detecting fluctuations in corneal sensitivity.