Campus Units

Biomedical Sciences, Veterinary Diagnostic and Production Animal Medicine, Veterinary Clinical Sciences

Document Type


Publication Version

Accepted Manuscript

Publication Date


Journal or Book Title

Veterinary Ophthalmology




Objective To investigate the effects of various biological factors on total protein concentration (TPC) and serum albumin levels in canine tears.

Animals studied 10 healthy beagles (5 female, 5 male) were used.

Procedures Experiments were conducted on separate days, collecting tears with either capillary tubes or Schirmer strips, as follows: (i) Tear collection at 3 hours intervals (from 6 am to 12 am); and (ii) Tear collection before and 20 minutes following topical histamine application (1, 10, 375 mg/mL) to induce mild, moderate, and severe conjunctivitis, respectively. TPC and serum albumin were measured with infrared spectroscopy and ELISA, respectively.

Results Tear film TPC and serum albumin ranged from 9.7‐26.1 mg/mL and 6.4‐1662.6 µg/mL, respectively. Protein levels did not differ significantly among time points (P ≥ .080). Median coefficient of variation (CV%) was lower with Schirmer strips compared to capillary tubes for both TPC (12% vs 15%, P = .020) and serum albumin (57% vs 78%, P = .232). TPC (P < .001), but not serum albumin was greater in male vs. female dogs. Serum albumin, but not TPC (P ≥ .099), increased significantly with each grade of conjunctivitis severity (P < .001), with no differences between collection devices (P ≥ .322); median increase was 106%, 1389%, and 2871% in eyes with mild, moderate, and severe conjunctivitis, respectively.

Conclusions There is no apparent diurnal variation in canine tear protein levels. Blood‐tear barrier breakdown with conjunctivitis allows serum albumin to leak into the tear film at high concentrations. Schirmer strips compare well with capillary tubes for bioanalytical purposes in healthy and diseased eyes, and this collection method may offer improved reproducibility for protein quantification.


This is the peer-reviewed version of the following article: Page, Lauren, Rachel A. Allbaugh, Jonathan P. Mochel, Jacqueline Peraza, Morgan Bertram, and Lionel Sebbag. "Impact of diurnal variation, sex, tear collection method, and disease state on tear protein levels in dogs." Veterinary Ophthalmology (2020), which has been published in final form at DOI: 10.1111/vop.12840. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. Posted with permission.

Copyright Owner

American College of Veterinary Ophthalmologists



File Format


Available for download on Thursday, October 28, 2021

Published Version