Schirmer tear test type I readings and intraocular pressure values assessed by applanation tonometry (Tonopen®XL) in normal eyes of four European species of birds of prey

Abstract

To determine normal values for Schirmer tear test I and intraocular pressure in four European species of birds of prey. Twenty birds from each of the following species: Eurasian Tawny owl (Strix aluco), Little owl (Athene noctua), Common buzzard (Buteo buteo), and European kestrel (Falco tinnunculus). Both eyes of all birds (80 eyes) underwent a complete ophthalmic examination, which included a Schirmer tear test type I (STT-I) performed with commercially available strips and the assessment of the intraocular pressure (IOP) by applanation tonometry, employing the Tonopen-XL(®) device. The animals, which had been taken to a rescue center, were examined for ocular lesions prior to their eventual release into the wild. STT-I readings and IOP values were expressed as means±standard deviation. Schirmer tear test type I readings were as follows: Eurasian Tawny owls: 3.12±1.92mm/min; Little owls: 3.5±1.96mm/min; Common buzzards: 12.47±2.66mm/min; European kestrels: 6.20±3.67mm/min. IOP values were as follows: Eurasian Tawny owls: 11.21±3.12mmHg; Little owls: 9.83±3.41mmHg; Common buzzards: 17.2±3.53mmHg; European kestrels: 8.53±1.59mmHg. The results of this study give representative values for STT-I and IOP in four of the most common species of birds of prey in Europe.