Comparing the effects of intraocular pressure and tear production measurements in horses in two different environments: Horse stable and medical barn.
Authors: Cinar Harun, Yanmaz Latif Emrah, Buyukkaraca Nurefsan, Kaya Zehranur, Kosuncu Mirkan
Journal: Equine veterinary journal
Summary
# Environmental Effects on Equine Ocular Measurements This research directly addresses a gap in equine ophthalmology: whether measuring intraocular pressure (IOP) and tear production in an unfamiliar clinical setting produces meaningfully different results compared to the horse's home stable. Using a crossover design with 30 healthy Arabian stallions (mean age 6.88 years), researchers measured both parameters in each environment and employed paired t-tests and Bland-Altman analysis to detect differences and assess measurement agreement. IOP rose significantly in the medical barn (34.2 mmHg) relative to the stable (29.5 mmHg)—a difference of 4.7 mmHg that was statistically significant—whereas tear production showed no meaningful variation between locations (22.1 mm/min in the stable versus 23.6 mm/min in the barn, p = 0.09). The Bland-Altman analysis revealed systematic bias in both measurements depending on location, with IOP showing the greater discrepancy. For practitioners conducting ophthalmic examinations or establishing baseline values for glaucoma screening, these findings underscore the importance of environmental standardisation; the substantial IOP elevation in an unfamiliar clinical environment could lead to false clinical interpretations or inappropriate intervention in horses with borderline pressure readings, making stable-based assessment potentially more physiologically representative for diagnostic purposes.
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Practical Takeaways
- •IOP measurements in horses may be artificially elevated in unfamiliar medical settings; baseline values from familiar environments should be considered when interpreting clinical measurements
- •Environmental stress affects ocular pressure but not tear production in healthy horses, suggesting different physiological pathways for these parameters
- •When evaluating horses for glaucoma or ocular disease, practitioners should account for measurement location and environmental familiarity, as these can create clinically significant differences in IOP readings
Key Findings
- •IOP was significantly higher in the medical barn (34.2 ± 6.8 mmHg) compared to the horse stable (29.5 ± 7.2 mmHg, p = 0.02), with a difference of 4.7 mmHg
- •Tear production showed no statistically significant difference between horse stable (22.1 ± 2.8 mm/min) and medical barn (23.6 ± 3.4 mm/min, p = 0.09)
- •Bland-Altman analysis revealed systematic discrepancies in IOP measurements between environments, suggesting environmental influence on ocular measurements
- •Environment appears to be a significant variable affecting intraocular pressure measurements in horses but not tear production