Effects of action of proparacaine and tetracaine topical ophthalmic formulations on corneal sensitivity in horses.
Abstract: To compare the corneal anesthetic effects and duration of action of 2 ophthalmic anesthetic agents in horses. Methods: Prospective, randomized masked crossover study. Methods: 8 clinically normal adult horses. Methods: Corneal sensitivity was determined by measuring each eye's corneal touch threshold (CTT) with a Cochet-Bonnet esthesiometer. Each eye's baseline CTT was recorded prior to anesthetic instillation at 0 minutes and every 10 minutes thereafter for 60 minutes. Each eye was randomly assigned to receive 2 of 4 treatments: 0.5% aqueous proparacaine ophthalmic solution (aqueous proparacaine; 8 eyes); 0.5% aqueous tetracaine ophthalmic solution (aqueous tetracaine; 8 eyes); 0.5% viscous tetracaine ophthalmic solution (viscous tetracaine; 8 eyes); and saline (0.9% NaCl) eyewash solution (8 eyes) as a negative control. There was a 48-hour washout period. Every horse received all treatments. Results: Median baseline CTT of eyes was 4.5 cm (range, 0.5 to 6 cm). Median CTT for saline solution-treated eyes never differed significantly from baseline. The maximum anesthetic effect with the other 3 treatments occurred at 10 minutes. Median CTT of eyes at 10 minutes was 0.5 cm (range, 0 to 2.5 cm) with aqueous proparacaine treatment, 0.25 cm (range, 0 to 2.0 cm) with aqueous tetracaine treatment, and 0 cm (range, 0 to 0.5 cm) with viscous tetracaine treatment. Maximum anesthetic duration was 20 minutes with aqueous proparacaine and aqueous tetracaine treatments and 30 minutes with viscous tetracaine treatments. Conclusions: Treatment of eyes with viscous tetracaine resulted in the greatest decrease in CTT and the longest duration of action, compared with treatment with aqueous proparacaine or aqueous tetracaine.
Publication Date: 2012-12-12 PubMed ID: 23216041DOI: 10.2460/javma.241.12.1645Google Scholar: Lookup
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- Journal Article
- Randomized Controlled Trial
Summary
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The research article is a study comparing the effects and duration of two types of ophthalmic anaesthetic agents, proparacaine and tetracaine, on the corneal sensitivity in horses.
Study Methodology
- The study was organized as a prospective, randomized masked crossover experiment involving 8 regular adult horses.
- Each horse’s corneal sensitivity, referred to as corneal touch threshold (CTT), was determined using a Cochet-Bonnet esthesiometer, a tool for measuring sensitivity and nerve function in the cornea.
- Prior to administering the anesthetic agents, baseline CTT values were recorded for both eyes of each horse. Each eye was then randomly chosen to receive one of four treatments.
- The treatments included 0.5% aqueous proparacaine, 0.5% aqueous tetracaine, 0.5% viscous tetracaine, or a 0.9% NaCl saline solution which acted as a negative control. A 48-hour washout period was observed to ensure removal of any residual substances before administering a new treatment.
- All horses received every treatment, and following the application, the CTT of each eye was measured at 10 minute intervals for a total of 60 minutes to track the progression and timeline of the anesthetic effects.
Findings of the Study
- The median baseline CTT of the horses’ eyes was calculated as 4.5 cm, with a range from 0.5 to 6 cm.
- It was found that the CTT for the eyes treated with the saline solution never significantly differed from the baseline, proving its efficacy as a control.
- The maximum anesthetic effect with the other treatments was observed at 10 minutes. Aqueous proparacaine reduced the CTT to 0.5 cm, aqueous tetracaine to 0.25 cm, while viscous tetracaine reduced it to 0 cm, indicating complete corneal numbness.
- Upon comparison of the duration of the anesthetic effects, both aqueous proparacaine and aqueous tetracaine lasted for 20 minutes, while viscous tetracaine lasted for a longer period of 30 minutes.
Conclusion of the Research
- The study demonstrated that the treatment of eyes with viscous tetracaine led to a greater decrease in the horse’s corneal sensitivity and the longest duration of action, compared to the other two treatments with aqueous proparacaine or aqueous tetracaine.
Cite This Article
APA
Sharrow-Reabe KL, Townsend WM.
(2012).
Effects of action of proparacaine and tetracaine topical ophthalmic formulations on corneal sensitivity in horses.
J Am Vet Med Assoc, 241(12), 1645-1649.
https://doi.org/10.2460/javma.241.12.1645 Publication
Researcher Affiliations
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, 48823, USA.
MeSH Terms
- Administration, Topical
- Anesthesia, Local / veterinary
- Anesthetics, Local / administration & dosage
- Anesthetics, Local / pharmacology
- Animals
- Cornea / drug effects
- Cross-Over Studies
- Horse Diseases / drug therapy
- Horses
- Ophthalmic Solutions
- Propoxycaine / administration & dosage
- Propoxycaine / pharmacology
- Tetracaine / administration & dosage
- Tetracaine / pharmacology
Citations
This article has been cited 2 times.- Mecum NE, Demers D, Sullivan CE, Denis TE, Kalliel JR, Meng ID. Lacrimal gland excision in male and female mice causes ocular pain and anxiety-like behaviors.. Sci Rep 2020 Oct 14;10(1):17225.
- Sanchez MF, Breda SA, Soria EA, Tártara LI, Manzo RH, Olivera ME. Ciprofloxacin-lidocaine-based hydrogel: development, characterization, and in vivo evaluation in a second-degree burn model.. Drug Deliv Transl Res 2018 Oct;8(5):1000-1013.
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