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Effect of multiple head positions on intraocular pressure in healthy, anesthetized horses during hoisting
Author(s) -
Alling Christopher R.,
Cremer Jeannette,
Liu ChinChi,
Lewin Andrew C.,
CamachoLuna Pilar,
Carter Renee T.
Publication year - 2021
Publication title -
veterinary ophthalmology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.594
H-Index - 50
eISSN - 1463-5224
pISSN - 1463-5216
DOI - 10.1111/vop.12849
Subject(s) - xylazine , intraocular pressure , detomidine , medicine , ketamine , anesthesia , butorphanol , premedication , halothane , ophthalmology
Objective 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. Animals studied Seventeen healthy adult horses without significant ocular abnormalities. Procedures 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.