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American journal of veterinary research1995; 56(2); 155-158;

Effect of auriculopalpebral nerve block and intravenous administration of xylazine on intraocular pressure and corneal thickness in horses.

Abstract: Intraocular pressure (IOP) was measured, using applanation tonometry, in both eyes of 20 horses after topical application of 0.5% proparacaine to the cornea. Ultrasonic pachymetry was used to measure central, mid-peripheral, and peripheral corneal thickness (CT) in all 4 quadrants of both eyes of 25 horses. All measurements were repeated after auriculopalpebral nerve block, sedation by IV administration of xylazine, or combination of nerve block and sedation. Mean IOP after topical anesthesia of the cornea was 20.6 +/- 4.7 mm of Hg for the left eye and 20.35 +/- 3.7 mm of Hg for the right eye. Mean central CT was 793.2 +/- 42.3 microns. The peripheral part of the cornea was significantly (P < 0.05) thicker, on average, than the central part of the cornea. Auriculopalpebral nerve block had no significant effect on IOP or CT. Intravenous administration of xylazine resulted in a significant (P < 0.05) decrease in IOP, but had no effect on CT.
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Publication Date: 1995-02-01 PubMed ID: 7717576
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

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 the effects of auriculopalpebral nerve blocking and intravenous xylazine on intraocular pressure and corneal thickness in horses. The results suggest that while the auriculopalpebral nerve block had no significant impact on either parameter, xylazine administration led to a substantial decrease in intraocular pressure without affecting the corneal thickness.

Methodology and Procedure

  • The researchers measured the Intraocular pressure (IOP) in both eyes of 20 horses with the use of applanation tonometry, a method used to measure the fluid pressure inside the eye, after applying 0.5% proparacaine to the cornea for anesthesia.
  • The thickness of the cornea, at various areas including central, mid-peripheral and peripheral, was measured in all four quadrants of both eyes of 25 horses using Ultrasonic pachymetry.
  • The measurements were then performed again after administering auriculopalpebral nerve block (a procedure to induce topical anesthesia), intravenous administration of xylazine (a drug often used for sedation, analgesia, and muscle relaxation), or a combination of both procedures to assess the impact of these factors on both intraocular pressure and corneal thickness in horses.

Results

  • The average IOP after local cornea anesthesia was 20.6 +/- 4.7 mm of Hg for the left eye and 20.35 +/- 3.7 mm of Hg for the right eye.
  • The average central corneal thickness was 793.2 +/- 42.3 microns.
  • The peripheral part of the cornea was notably thicker than the central part of the cornea, a finding that was statistically significant (P < 0.05).
  • Auriculopalpebral nerve block did not significantly alter the IOP or the corneal thickness.
  • The administration of xylazine intravenously caused a significant (P < 0.05) decrease in IOP but did not alter the corneal thickness.

Conclusion

  • The study suggests that the administration of xylazine leads to a considerable decrease in the intraocular pressure in the eyes but does not impact the thickness of the cornea in horses.
  • The auriculopalpebral nerve block, on the other hand, did not influence either of these parameters significantly.

Cite This Article

APA
van der Woerdt A, Gilger BC, Wilkie DA, Strauch SM. (1995). Effect of auriculopalpebral nerve block and intravenous administration of xylazine on intraocular pressure and corneal thickness in horses. Am J Vet Res, 56(2), 155-158.

Publication

American journal of veterinary research
ISSN: 0002-9645
NlmUniqueID: 0375011
Country: United States
Language: English
Volume: 56
Issue: 2
Pages: 155-158

Researcher Affiliations

van der Woerdt, A
  • Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Ohio State University, Columbus 43210, USA.
Gilger, B C
    Wilkie, D A
      Strauch, S M

        MeSH Terms

        • Animals
        • Cornea / anatomy & histology
        • Cornea / drug effects
        • Female
        • Horses / physiology
        • Injections, Intravenous
        • Intraocular Pressure / drug effects
        • Male
        • Nerve Block / veterinary
        • Xylazine / pharmacology

        Citations

        This article has been cited 9 times.
        1. Knickelbein KE, Lassaline ME, Kim S, Scharbrough MS, Thomasy SM. Corneal thickness and anterior chamber depth of the normal adult horse as measured by ultrasound biomicroscopy. Vet Ophthalmol 2022 May;25 Suppl 1(Suppl 1):17-24.
          doi: 10.1111/vop.12971pubmed: 35084084google scholar: lookup
        2. 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
        3. Rizk A, Nocera I, Briganti A, Abouelnasr K, El-Khodery S, Tagawa M, Bonelli F. Dose-dependent effect of romifidine on intraocular pressure in clinically healthy buffalo (Bubalus bubalis). Heliyon 2019 Dec;5(12):e02930.
          doi: 10.1016/j.heliyon.2019.e02930pubmed: 31867457google scholar: lookup
        4. Sandmeyer LS, Leis M, Osinchuk S. Diagnostic Ophthalmology. Can Vet J 2019 Jul;60(7):789-790.
          pubmed: 31281201
        5. Gemensky-Metzler AJ, Wilkie DA, Weisbrode SE, Kuhn SE. The location of sites and effect of semiconductor diode trans-scleral cyclophotocoagulation on the buphthalmic equine globe. Vet Ophthalmol 2014 Jul;17 Suppl 1(0 0):107-16.
          doi: 10.1111/vop.12166pubmed: 24697980google scholar: lookup
        6. Holve DL, Gum GG, Pritt SL. Effect of sedation with xylazine and ketamine on intraocular pressure in New Zealand white rabbits. J Am Assoc Lab Anim Sci 2013 Jul;52(4):488-90.
          pubmed: 23849448
        7. Andrade SF, Kupper DS, Pinho LF, Franco EC, Prataviera MV, Duarte RR, Junqueira JR. Evaluation of the Perkins handheld applanation tonometer in horses and cattle. J Vet Sci 2011 Jun;12(2):171-6.
          doi: 10.4142/jvs.2011.12.2.171pubmed: 21586877google scholar: lookup
        8. 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
        9. 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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