Tear ferning test in horses and its correlation with ocular surface evaluation.

Abstract

OBJECTIVE: To describe the tear ferning test (TFT) in healthy horses and its correlation with other parameters for evaluating the ocular surface. ANIMALS STUDIED: Thirty male and female adult healthy horses (60 eyes), of no defined breed. PROCEDURES: Tear sample was collected with a microcapillary tube, placed on the surface of a glass slide, and allowed to dry at room temperature. The crystallization pattern was classified according to Rolando (Chibret International Journal Ophthamology, 1984; 2, 32). The program STEPanizer(&#xa9;) stereology tool, version 1.0, was utilized for counting points on the digitally captured crystallization image. A conjunctival biopsy was performed. RESULTS: Tear ferning test was classified as Type I in 18 eyes (30%), Type II in 31 eyes (51.7%), and Type III in 11 eyes (18.3%), at a mean temperature of 27.3&#xa0;&#xb1;&#xa0;1.5&#xa0;&#xb0;C and relative humidity of 61.5&#xa0;&#xb1;&#xa0;5.7%. In the Type I crystallization, the count varied between 27 and 36 points (mean: 33.27&#xa0;&#xb1;&#xa0;2.40), in Type II between 22 and 31 points (25.42&#xa0;&#xb1;&#xa0;1.95), and in Type III between 13 and 25 points (16.82&#xa0;&#xb1;&#xa0;3.76). There was no statistical difference or correlation between the right and left eyes, nor was there a statistically significant influence (P&#xa0;<&#xa0;0.05) on TFT by the factors evaluated. The mean goblet cells values were 50&#xa0;&#xb1;&#xa0;11.4 cells/field. All samples showed the presence of lymphocytes, plasmocytes, and eosinophils. CONCLUSION: Tear ferning test is easy to perform, without risks to the patient. Once standardized for horses, associated or not with the program STEPanizer(&#xa9;) stereology tool, it is an additional method for evaluating the ocular surface.