Assessment of lipid layer patterns in domestic dogs and rabbits: an observational study

Abstract

Background: Maintaining a stable tear film is crucial for having healthy human and animal vision. Animals are expected to have thicker lipid layers than humans due to living in high-temperature and humid environments.

Aim: The study aimed to evaluate the lipid layer patterns (LLPs) in Arabian dogs and rabbits using a non-invasive, practical, and easy-to-use device and compare them to humans with healthy eyes.

Methods: The study included 75 domestic Arabian dogs (42 males and 33 females; mean ± SD = 6.1 ± 12.7 months) and 75 rabbits (37 males and 38 females; mean ± SD = 3.1 ± 3.4 months). In addition, 75 individuals with healthy eyes (39 males and 36 females; mean ± SD = 25.7 ± 5.0 years) were included for comparison. EASYTEAR View+ assessed the LLP in each animal's and individual's right eye.

Results: The median LLP grades significantly differed between dogs and humans (Mann-Whitney U test, p < 0.001). Similarly, the LLP grades differed significantly between rabbits and humans (Mann-Whitney U test, p < 0.001). No significant difference (Mann-Whitney U test) in the LLP grades between dogs and rabbits was found. The analysis indicated that most dogs had either an A (34.7%) or a B grade (37.3%). Similarly, rabbits had predominantly A or 1 (46.7%) and B (30.7%) grades. On the other hand, humans had predominantly D (53.3%) and E (30.7%) grades.

Conclusion: The EASYTEAR View+ has been employed to assess LLP in dogs and rabbits, and the measurements were compared to those of humans with normal ocular health. Dogs and rabbits have thinner lipid layers than healthy humans.

Keywords: Dogs; Dry eye; Lipid layer patterns; Rabbits; Tear film.

Fig. 1.. Side-by-side boxplots of the LLP scores in dogs, rabbits, and healthy-eye humans. The grades are categorized as follows: grade A or 1 (showing a grayish appearance, with LLT = 13–15 nm), grade B or 2 (more compact with LLT = 30–50 nm), grade C or 3 (gray waves with LLT = 50–80 nm), grade D or 4 (dense white-blue layer, with LLT = approximately 80 nm), and grade E or 5 (showing variable colors, with LLT = 90–140 nm)

Fig. 2.. The LLP in dogs, rabbits, and healthy-eyed humans. The grades are categorized as follows: grade A or 1 (showing a grayish appearance, with LLT = 13–15 nm), grade B or 2 (more compact with LLT = 30–50 nm), grade C or 3 (gray waves with LLT = 50–80 nm), grade D or 4 (dense white-blue layer, with LLT = approximately 80 nm), and grade E or 5 (showing variable colors, with LLT = 90–140 nm).