Comparison of tear pH in dogs, horses, and cattle.
Abstract: To determine baseline tear pH in dogs, horses, and cattle by use of a microelectrode. Methods: 28 dogs, 24 horses, and 29 cattle. Methods: Under manual restraint, tears were collected from each subject's left eye with cotton spears. A Schirmer tear test was performed in the right eye. Tears were extracted from the spears by centrifugation. Tear volume was measured, pH was determined with a microelectrode, and total solids (TS) concentration was measured by refractometry. Results: Mean ± SD pH of tears in cattle, dogs, and horses was 8.32 ± 0.14, 8.05 ± 0.26, and 7.84 ± 0.30, respectively. Tear pH was significantly higher in cattle versus dogs and horses and in dogs versus horses. Mean ± SD TS concentration in horses, cattle, and dogs was 2.04 ± 1.29 g/dL, 1.07 ± 0.60 g/dL, and 0.33 ± 0.18 g/dL, respectively. Total solids concentration was significantly higher in horses versus cattle and dogs and in cattle versus dogs. Schirmer tear test results for all animals were within the species reference range. Conclusions: Tear pH in all 3 species differed from that of published blood pH values and the pH of common topically administered ophthalmic medications. These fndings may have implications for variations in ocular flora and defense mechanisms, susceptibility to ocular disease, and success or comfort of topical treatment.
Publication Date: 2014-04-26 PubMed ID: 24762022DOI: 10.2460/ajvr.75.5.494Google Scholar: Lookup
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- Comparative Study
- Journal Article
Summary
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The research study compares the pH level of tears in three different animal species: dogs, horses, and cattle. The results reveal significant differences in tear pH and total solid concentration among these species, which could potentially influence their susceptibility to ocular disease and the effectiveness of eye treatments.
Experiment Procedure
- The study involved 28 dogs, 24 horses, and 29 cattle. Under manual restraint, tears were collected from each subject’s left eye using cotton spears.
- The tear volume was measured, and the pH was determined using a microelectrode.
- A Schirmer tear test, which measures the rate of tear production, was conducted in the right eye of each subject.
- The total solids (TS) concentration of the tears was measured using refractometry, a method that measures pressure as light travels through a liquid.
Results
- The mean pH of cattle tears was found to be higher (8.32 ± 0.14) compared to dogs (8.05 ± 0.26) and horses (7.84 ± 0.30).
- The total solids concentration was significantly higher in horses (2.04 ± 1.29 g/dL) compared to cattle (1.07 ± 0.60 g/dL) and dogs (0.33 ± 0.18 g/dL).
- Results from the Schirmer tear test in all three species were within the appropriate reference range for each species.
Conclusions
- The pH of tears in dogs, horses, and cattle differed from the pH values of blood and from commonly administered ophthalmic medications.
- These differences may influence variations in ocular flora (microorganisms in the eye) and defense mechanisms, an animal’s susceptibility to ocular diseases, and the effectiveness and comfort of topical treatments.
Cite This Article
APA
Beckwith-Cohen B, Elad D, Bdolah-Abram T, Ofri R.
(2014).
Comparison of tear pH in dogs, horses, and cattle.
Am J Vet Res, 75(5), 494-499.
https://doi.org/10.2460/ajvr.75.5.494 Publication
Researcher Affiliations
- Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, 7610001, Israel.
MeSH Terms
- Analysis of Variance
- Animals
- Cattle
- Data Collection
- Dogs
- Female
- Horses
- Hydrogen-Ion Concentration
- Male
- Ophthalmic Solutions / chemistry
- Refractometry / veterinary
- Tears / chemistry
Citations
This article has been cited 5 times.- Stolle LM, Oltmanns H, Meißner J, Heun F, Schieder AK, Wolff HT, Ohnesorge B, Busse C. Polyhexanide, Povidone-Iodine, and Hypochlorous Acid Show High In Vitro Antimicrobial Efficacy Against Pathogens Commonly Associated With Equine Infectious Keratitis. Vet Ophthalmol 2026 Jan;29(1):e70141.
- Santos G, Delgado E, Silva B, Braz BS, Gonçalves L. Topical Ocular Drug Delivery: The Impact of Permeation Enhancers. Pharmaceutics 2025 Mar 31;17(4).
- Pe'er O, Sebbag L, Zahavi A, Girshevitz O, Goldenberg-Cohen N, Ofri R. Trace Element Levels in Canine Tear Film. Vet Ophthalmol 2026 Jan;29(1):e70004.
- Handel KW, Ofri R, Goncharov Y, Arad D, Sebbag L. Evaluation of 0.1% and 1% atropine eyedrops in cats: A comparative study of tolerance, stability, and efficacy. Vet Ophthalmol 2025 Jul;28(4):714-721.
- Ibrahim A, Abd-Elrasoul MAA, Sabra MS. Impact of pH modification of the empirically used tobramycin ophthalmic solution on MIC90 concentration in tears and aqueous humor of donkeys (Equus asinus). BMC Vet Res 2024 May 23;20(1):218.
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