Fig. 1

Examples of tear ferning patterns in cats according to (a–c) the Rolando and d–f) the Masmali grading scales. a Type I representation: dendritic fern growth is uniform, nuclei (yellow arrows) are easily distinguished and no gaps are seen between the branches. b Type II: small spaces (green arrows) begin to appear between the branches and the ferns are thicker. c Type III: incomplete crystallization process; coarse crystals (red arrows) are formed in single and small size, and branches are rare. d Grade 0 representation: full crystallization without gaps between the ferns and branches, and nuclei well demarcated. e Grade 1: branch density is decreased and small spaces appear between them. f Grade 2: small branches—sometimes thick and large—with clear gaps between the ferns (blue arrows), and nuclei not visible. Note the similarity between panel (a) and (d); between (b) and (e); Furthermore panel (b) is closer to (e), whereas (b) and (f) appear more similar than (c) and (f), suggesting that Roland type I is similar to Masmali grade 0, and Rolando type II shares some common features with both Masmali grades 1 and 2