A comparative study of corneal sensitivity in birds of prey

Objective: To determine and compare the corneal sensitivity in healthy wild diurnal and nocturnal birds of prey (BP) indigenous to Catalonia (Spain), and to establish if age is a determining factor in corneal sensitivity in those species. Methods: Ophthalmic examination was performed in 105 BP. Only birds with no ocular abnormalities were included in the study (n = 81): 21 diurnal BP (Falco tinnunculus: 16 fledglings, 5 adults) and 60 nocturnal BP (20 Athene noctua [9 fledglings, 11 adults], 20 Strix aluco [15 fledglings, 5 adults], and 20 Otus scops [6 fledglings and 14 adults]). Corneal touch threshold (CTT) was determined for each eye in five different corneal regions. Five attempts to cause a blink reflex were made in each region, and when three or more reflexes were positive, the pressure was deemed the CTT. Statistical analysis was performed using a Student's t-test for independent data or an anova model. The results between species and age groups were compared using the Generalized Estimated Equations model. Results: There were no significant differences between any of the corneal regions (P = 0.25), or between the right (CTT = 4.9 ± 1.7 cm) and left (CTT = 4.8 ± 1.7 cm) eye in any of the species (P = 0.692). No difference was found between diurnal and nocturnal species (P = 0.913). Considering all the species, a significant difference was found between the mean CTT of fledglings (5.4 ± 1.2 cm) and adults (4.1 ± 2 cm), P < 0.001. A significant difference was found between fledglings and adults of A. noctua (P < 0.001) and S. aluco (P = 0.002). Conclusions: There is no significant difference in CTT between the different corneal regions in all the species studied. Corneal sensitivity is similar between diurnal and nocturnal birds of prey. Age is a determining factor in the CTT of A. noctua and S. aluco, with fledglings having a significantly higher CTT. © 2013 American College of Veterinary Ophthalmologists.