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Veterinary ophthalmology2020; 24(1); 71-79; doi: 10.1111/vop.12849

Effect of multiple head positions on intraocular pressure in healthy, anesthetized horses during hoisting.

Abstract: To evaluate changes in intraocular pressure (IOP) with variable head position in healthy, anesthetized horses in hoisted inversion and to assess the influence of various cofactors (age, sex, body weight, body condition score, and neck length) on IOP changes during hoisting. Methods: Seventeen healthy adult horses without significant ocular abnormalities. Methods: Subjects were administered intravenous xylazine/butorphanol premedication and ketamine/midazolam induction with xylazine/ketamine boluses for anesthetic maintenance. While hoisted, IOP was measured in triplicate for each eye via rebound tonometry (TonoVet) at neutral head position (ie, eyes level with the withers), at multiple 5 cm increments above and below neutral (-20 cm through +20 cm) using foam pads for head support, and with eyes above heart level via manual support. Results: In hoisted positions, IOP ranged from 18 to 51 mmHg. Intraocular pressure significantly decreased with head position elevated ≥+15 cm from neutral and significantly increased when lowered ≤-5 cm from neutral. Neck length significantly influenced IOP (P = .0328) with linear regression indicating a median (range) increase of 0.244 (0.034-0.425) mmHg in IOP for every 1 cm increase in neck length. Age, sex, breed, body weight, body condition score, and eye (OD vs OS) did not significantly influence IOP. Intraocular pressure only varied significantly between eyes at +10 cm above neutral (OS > OD, 1.7 ± 0.6 mm Hg, P = .0044). Conclusions: Intraocular pressure in healthy, anesthetized horses varies with head position during hoisting; increased neck length may be associated with larger changes in IOP during hoisting.
© 2020 American College of Veterinary Ophthalmologists.
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Publication Date: 2020-12-02 PubMed ID: 33264475DOI: 10.1111/vop.12849Google Scholar: Lookup
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  • Clinical Trial
  • Veterinary
  • Journal Article

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.

This research investigates how varying the head position of anesthetized, healthy horses during hoisting impacts intraocular pressure (IOP). The study also explores the influence of different factors like age, body weight, and neck length on the change in IOP during hoisting.

Methods

  • Seventeen healthy adult horses with no notable ocular issues were involved in the study.
  • The horses were first given xylazine/butorphanol and then ketamine/midazolam induction, followed by xylazine/ketamine boluses to maintain the anesthesia.
  • The researchers measured the IOP thrice for each eye using TonoVet rebound tonometry.
  • These measurements were done at various head positions (from 20cm below to 20cm above neutral position and with eyes at heart level) under hoisted conditions. The neutral position was defined as when the horse’s eyes were at the same level as its withers.

Results

  • The intraocular pressure (IOP) ranged from 18 to 51 mmHg during hoisting.
  • IOP decreased significantly when the horse’s head was raised by 15 cm or more from the neutral position and increased significantly when lowered by 5 cm or less.
  • Changes in IOP were significantly influenced by the length of the horse’s neck, with an increase of 0.244 mmHg in IOP for every 1 cm increase in neck length.
  • Other factors like age, sex, breed, body weight, and body condition did not significantly influence IOP.
  • Significant variance in IOP between eyes was only seen at +10 cm above the neutral position.

Conclusions

  • There is a significant variation in the intraocular pressure of healthy, anesthetized horses during hoisting depending on the position of the head.
  • Increase in neck length could lead to larger changes in IOP during hoisting.

Cite This Article

APA
Alling CR, Cremer J, Liu CC, Lewin AC, Camacho-Luna P, Carter RT. (2020). Effect of multiple head positions on intraocular pressure in healthy, anesthetized horses during hoisting. Vet Ophthalmol, 24(1), 71-79. https://doi.org/10.1111/vop.12849

Publication

Veterinary ophthalmology
ISSN: 1463-5224
NlmUniqueID: 100887377
Country: England
Language: English
Volume: 24
Issue: 1
Pages: 71-79

Researcher Affiliations

Alling, Christopher R
  • Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
Cremer, Jeannette
  • Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
Liu, Chin-Chi
  • Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
Lewin, Andrew C
  • Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
Camacho-Luna, Pilar
  • Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
Carter, Renee T
  • Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.

MeSH Terms

  • Anesthesia / veterinary
  • Animals
  • Female
  • Head
  • Horses / physiology
  • Intraocular Pressure
  • Male
  • Posture
  • Restraint, Physical / veterinary

Grant Funding

  • LSU School of Veterinary Medicine

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Citations

This article has been cited 1 times.
  1. 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
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