Comparison of tear pH in dogs, horses, and cattle.
OBJECTIVE
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.
Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, 7610001, Israel.
Billie
B
Beckwith-Cohen
Daniel
D
Elad
Tali
T
Bdolah-Abram
Ron
R
Ofri
D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003625:Data Collection; D004285:Dogs; D005260:Female; D006736:Horses; D006863:Hydrogen-Ion Concentration; D008297:Male; D009883:Ophthalmic Solutions / Q000737:chemistry; D012031:Refractometry / Q000662:veterinary; D013666:Tears / Q000737:chemistry*
D009883:Ophthalmic Solutions