ESTIMATION OF NORMAL TEAR PRODUCTION IN FREE-LIVING EURASIAN BLACK VULTURES (AEGYPIUS MONACHUS) AND GRIFFON VULTURES (GYPS FULVUS) IN DADIA NATIONAL PARK, GREECE

Abstract

The aim of this study was to record the Schirmer tear test I (STT I) measurements in free-living vultures in order to estimate normal values. The Eurasian black vulture (Aegypius monachus), which breeds in the Mediterranean region and Asia, is listed as near threatened; it is also classified as vulnerable at the European level and endangered in Greece. The griffon vulture (Gyps fulvus), once widespread across the continent, has undergone a dramatic decline which has led to its extinction in many regions. Sixty-two animals were examined in total including 54 black vultures and 8 griffon vultures. The birds were classified into five age groups while four age groups were then combined into one large group: free-flying. STT I measurements and complete ophthalmic examinations were performed. Mean STT I value for black vultures was 10.9 +/- 3.3 mm/min (right eye, oculus dexter, OD) and 11.9 +/- 3.3 mm/min (left eye, oculus sinister, OS) and for griffon vultures was 6.4 +/- 1.8 mm/min OD and 6.5 +/- 1.8 mm/min OS. In both eyes, STT I values in black vultures were significantly higher than those recorded in griffon vultures. Intraspecific comparisons yielded a significant difference between eyes of black vultures but not between those of griffon vultures, with OS producing higher STT I readings than did OD. When STT I was compared between OD and OS for each age group separately, a statistically significant difference was detected in the immature and free-flying black vultures. In addition, black vulture hatchlings had a significantly higher tear production than did free-flying juveniles, immatures, subadults, and adults. STT I values in black vultures are similar to those reported in other Accipitriformes but are lower in griffon vultures. This difference is probably related to anatomic, evolutionary, and feeding factors and requires further investigation.

Measurement of tear production and intraocular pressure in ducks and geese

“…18 The effect of age was not assessed in this study because precise determination of age was not possible in our study population. In Humboldt penguins, 7 macaroni penguins, 8 rockhopper penguin, 8 Screech owls, 10 vultures, 12 ostriches, 13 and American flamingos, 21 the age and gender did not alter results of STT and/or IOP in studied animals. But as determined by Reuter and colleagues in some birds of prey (northern goshawks, common buzzards, and common kestrels), 18 younger birds had lower IOP values than did older birds.…”

“…17 Estimation of normal tear production is an essential tool for the identification of ocular surface diseases in any species. 12 The Schirmer tear test, modified Schirmer strips, and phenol red thread test have been used in different avian species to measure aqueous portion of tear film. Williams (1994) reports Schirmer tear test results of 8 AE 1.5 mm (mean AE SD) in large Psittaciformes such as African gray parrots (Psittacus erithacus) and 4.5 AE 1 mm in small species such as lories and conures.…”

Ophthalmic Diagnostic Tests and Ocular Findings in a Flock of Captive American Flamingos (Phoenicopterus ruber ruber)

“…25 Therefore, a reason for absence of dazzle in the flamingos is difficult to postulate. We used the brightest setting on a light source available from 7 ; however, the assessment of a dazzle reflex is sporadically reported in other avian species. The remainder of the neuro-ophthalmic examination was consistent with findings of other published reports in avian species, with only the direct pupillary light reflex being observed.…”

“…29,30 Mean tear production as measured by the mSTTI in our study was 12 mm/min; this value was higher than the mean tear measurement by STTI in most other bird studies, though values ranging from ,2 mm/min to over 16 mm/min have been reported. [2][3][4][5][7][8][9][10][11] Most of these other studies used an unmodified, standard STTI strip; direct comparison could be hindered by the modification of the test strip, which resulted in decreased surface area of the filter paper for litmus effect. Only one of these previously published studies 11 used the same modification of the STT strip in tawny owls; mean tear production was much lower in that group of birds at 3.2 mm wetting per minute, as compared with our group of flamingos.…”

“…To date, there are sporadic publications reporting results of aqueous tear production as measured by the Schirmer tear test and the phenol red thread test, [2][3][4][5][6][7][8][9][10][11] indirect tonometry, 2,4,5,8,10-18 conjunctival microbial flora, 5,10,19 and ultrasonographic findings 5,14,[20][21][22] in a small number of avian species ranging from large psittacine birds to raptors. Additionally, electroretinographic findings of retinal photoreceptor function have been reported in Hispaniolan Amazon parrots (Amazona ventralis) and in free-living raptors.…”