Assessment of Tear Film in Arabian Horses with a Portable Device Compared to Human’s Healthy Eyes

The stability of the tear film is essential to maintain healthy vision in animals and humans. Therefore, tear film should be assessed occasionally to detect any abnormalities, particularly those living in an environment with high temperature and humidity. The current study assessed the non-invasive tear breakup time (NITBUT), tear meniscus height (TMH), and lipid layer pattern (LLP) in Arabian horses and compared them to those of humans. The study involved a total of 94 Arabian horses and 94 humans with healthy eyes. Each subject's right eye tear film parameters were evaluated using the EASYTEAR View+, with a 5-minute interval between each test. The same examiner performed each test three times. The statistical analysis revealed significant differences in the NITBUT (P = 0.001) and LLP (P = 0.010) scores between horses and humans. The LLP analysis indicated that grade E or 5 (variable colors, lipid layer thickness, LLT, = 90–140 nm) was predominant in horses (N = 52, 55.3%). On the other hand, grade D or 4 (dense white-blue layer; around 80 nm) was common in humans with healthy eyes (N = 48, 51.1%). No significant difference (P = 0.191) in the TMH scores between horses and humans was found. In conclusion, horses have a longer tear breakup time and thicker lipid layer height than humans with healthy eyes. Their tear meniscus height is similar to that of healthy humans.