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Veterinary ophthalmology2020; 23(2); 368-373; doi: 10.1111/vop.12735

Effect of auriculopalpebral nerve block on equine intraocular pressure measured by rebound tonometry (TonoVet® ).

Abstract: To assess rebound tonometry intraocular pressure (IOP) in unsedated horses without and with auriculopalpebral (AP) nerve blocks. Methods: Twenty-two client- and twenty university-owned horses (84 total eyes) with unremarkable ophthalmic examinations were evaluated. Methods: One eye of each horse was chosen randomly, an AP block performed for that eye, and IOP measured in both eyes with a TonoVet . The process was repeated for the contralateral eye 72 hours later under the same conditions as the initial measurements. Horses were unsedated for nerve blocks and tonometry. Linear mixed-effects models were used for comparisons with statistical significance threshold of 0.05. Results: Overall, blocked eyes had an 0.8 mm Hg lower average IOP than unblocked eyes (P = .039). IOP for client-owned horses was on average 3.2 mm Hg lower than in UGA-owned horses (P = .025) and was more impacted by AP block (1.4 mm Hg lower average in client-owned blocked versus unblocked eyes (P = .006)). Block effectiveness was ranked on a subjective scale ("good", "poor", no block/control), and IOP was on average lower in eyes with a good block (P = .008). Conclusions: Although there were statistically significant differences in IOP between blocked and unblocked eyes, between client- and UGA-owned horses, and between eyes with good and poor AP blocks, these differences were not clinically significant. Thus, AP blocks remain a useful tool for evaluating equine ophthalmic health with minimal impact on IOP assessment.
© 2020 American College of Veterinary Ophthalmologists.
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Publication Date: 2020-01-07 PubMed ID: 31908137DOI: 10.1111/vop.12735Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article discusses how auriculopalpebral (AP) nerve blocks affect intraocular pressure (IOP) in horses, when measured by rebound tonometry. The study found that although AP blocks have minor impacts on IOP, they remain clinically useful for studying equine eye health.

Objective and Methodology

The aim of the study was to understand the impact of auriculopalpebral (AP) nerve blocks on intraocular pressure (IOP), measured using rebound tonometry.

  • The study was conducted on a total of 42 horses, which included 22 owned by clients and 20 owned by the university. This made for a total of 84 eyes that were examined.
  • The AP block was performed on one randomly selected eye of each horse and the IOP was then measured in both eyes using TonoVet.
  • This process was repeated on the other eye after a gap of 72 hours under the same conditions.
  • The horses were not sedated during the nerve blocks and tonometry, ensuring the conditions remained consistent.
  • Statistical comparisons were made using linear mixed-effects models and a statistical significance threshold of 0.05 was followed.

Results

  • The research indicated that the blocked eyes had an average IOP of 0.8 mm Hg lower than the unblocked eyes (P = .039).
  • Moreover, the client-owned horses had an average IOP that was 3.2 mm Hg lower than that of the university-owned horses (P = .025). The AP block had more impact on client-owned horses, with an average drop of 1.4 mm Hg in the blocked versus unblocked eyes (P = .006).
  • The effectiveness of the AP block was noted on a subjective scale ranging from “good”, “poor”, to “no block/control”. The study found that the average IOP was lower in the eyes where a “good” block was performed (P = .008).

Conclusions

While the study found statistically significant differences in IOP between blocked and unblocked eyes, as well as between client- and university-owned horses, and between eyes with good and poor AP blocks, these variations were not clinically significant. Therefore, the researchers concluded that AP blocks can continue to serve as a reliable tool for studying equine eye health as they have minimal impact on the IOP assessment.

Cite This Article

APA
Diehl K, Bowden AC. (2020). Effect of auriculopalpebral nerve block on equine intraocular pressure measured by rebound tonometry (TonoVet® ). Vet Ophthalmol, 23(2), 368-373. https://doi.org/10.1111/vop.12735

Publication

Veterinary ophthalmology
ISSN: 1463-5224
NlmUniqueID: 100887377
Country: England
Language: English
Volume: 23
Issue: 2
Pages: 368-373

Researcher Affiliations

Diehl, Kathryn
  • University of Georgia College of Veterinary Medicine, Athens, GA, USA.
Bowden, Anna Catherine
  • University of Georgia College of Veterinary Medicine, Athens, GA, USA.

MeSH Terms

  • Animals
  • Female
  • Horses / physiology
  • Intraocular Pressure / drug effects
  • Male
  • Nerve Block / adverse effects
  • Nerve Block / veterinary
  • Tonometry, Ocular / veterinary

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This article includes 24 references
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Citations

This article has been cited 3 times.
  1. Mustikka MP, Pietilä EM, Mykkänen AK, Grönthal TSC. Comparison of two rebound tonometers in healthy horses. Vet Ophthalmol 2020 Sep;23(5):892-898.
    doi: 10.1111/vop.12819pubmed: 32888242google scholar: lookup
  2. Allen R, Goodhead AD. A survey of ocular pathology in Warmblood horses in South Africa. Equine Vet J 2025 Jul;57(4):889-897.
    doi: 10.1111/evj.14427pubmed: 39535442google scholar: lookup
  3. Preston JF, Mustikka MP, Priestnall SL, Dunkel B, Fischer MC. Clinical features and outcomes of horses presenting with presumed equine immune mediated keratitis to two veterinary hospitals in the United Kingdom and Finland: 94 cases (2009-2021). Equine Vet J 2025 May;57(3):598-610.
    doi: 10.1111/evj.14213pubmed: 39183684google scholar: lookup
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