Comparative evaluation of aqueous humor viscosity.

OBJECTIVE: To evaluate aqueous humor viscosity in the raptor, dog, cat, and horse, with a primary focus on the barred owl (Strix varia). ANIMALS STUDIED: Twenty-six raptors, ten dogs, three cats, and one horse. PROCEDURE: Animals were euthanized for reasons unrelated to this study. Immediately, after horizontal and vertical corneal dimensions were measured, and anterior chamber paracentesis was performed to quantify anterior chamber volume and obtain aqueous humor samples for viscosity analysis. Dynamic aqueous humor viscosity was measured using a dynamic shear rheometer (AR 1000 TA Instruments, New Castle, DE, USA) at 20 °C. Statistical analysis included descriptive statistics, unpaired t-tests, and Tukey's test to evaluate the mean ± standard deviation for corneal diameter, anterior chamber volume, and aqueous humor viscosity amongst groups and calculation of Spearman's coefficient for correlation analyses. RESULTS: The mean aqueous humor viscosity in the barred owl was 14.1 centipoise (cP) ± 9, cat 4.4 cP ± 0.2, and dog 2.9 cP ± 1.3. The aqueous humor viscosity for the horse was 1 cP. CONCLUSIONS: Of the animals evaluated in this study, the raptor aqueous humor was the most viscous. The aqueous humor of the barred owl is significantly more viscous than the dog (P < 0.0001). The aqueous humor viscosity of the raptor, dog, cat, and horse can be successfully determined using a dynamic shear rheometer.

Tear-film osmolarity in normal cats and cats with conjunctivitis.

OBJECTIVE: To compare the tear-film osmolarity of normal cats and cats with conjunctivitis. ANIMAL STUDIED: The population consisted of shelter, research, and privately owned cats. PROCEDURES: Cats were classified as normal or having conjunctivitis. An ophthalmic examination including Schirmer tear test (STT), fluorescein staining, tear-film break-up time (TFBUT), intraocular pressure (IOP), and slit-lamp biomicroscopy of the anterior segment was performed. The severity of conjunctivitis was graded and assigned a numerical score. The Tear Lab(TM) Osmolarity System was utilized to determine the tear-film osmolarity. Unpaired t-tests were used to compare tear-film osmolarity, TFBUT, IOP, and STT of the two groups. RESULTS: A total of 93 cats (186 eyes) were examined. There were 37 normal cats (74 eyes) and 39 conjunctivitis cats (78 eyes). The mean age was 2.34 years. There was no statistical difference (P = 0.2065) between the median tear-film osmolarity of normal cats (328.5 ± 17.94 mOsms/L) and conjunctivitis cats (325.0 ± 24.84 mOsms/L). Cats with conjunctivitis had an accelerated TFBUT (P < 0.0001) and lower IOPs (P < 0.0001) as compared to normal cats. No statistical difference was found between STT values (P = 0.1304). CONCLUSIONS: The median tear-film osmolarity of normal cats was 328.5 mOsms/L. Despite the accelerated TFBUT, conjunctivitis did not cause a statistically significant change in tear-film osmolarity. The Tear Lab(TM) Osmolarity System was easily used and well tolerated by the cats in the study.