Tear production and intraocular pressure values in clinically normal eyes of whooper swans (Cygnus cygnus)

• Published in: Open Veterinary Journal
• Main Authors: Liga Kovalcuka, Dmitrij Boiko, David L. Williams
• Format: Article in Journal/Newspaper
• Language: English
• Published: Tripoli University 2018
• Subjects: Eye; Intraocular pressure; Phenol red thread test; Tear production; Whooper swan; Zoology; QL1-991; Cygnus cygnus; Whooper Swan
• Online Access: https://doi.org/10.4314/ovj.v8i3.14; https://doaj.org/article/03e90587bc344f02a3a3ad2ce044a1ec

The objective of this study was to determine the normal range of tear production and values of intraocular pressure (IOP) in clinically normal eyes of whooper swans (Cygnus cygnus). A total of 86 birds: 81 cygnets (6-10 weeks old) and 5 moulting – adult swans (3-6 years old) were examined in this study. Both eyes of all birds underwent a complete ophthalmic examination, including evaluation of tear production with the phenol red thread test (PRTT) and the assessment of the IOP by rebound tonometry, employing the TonoVet® device. The mean ± standard deviation of PRTT values were as follows: all cygnets (81) 22.59±3.48 mm/15s, male cygnets (45) 22.64±3.54 mm/15s, female cygnets (36) 22.53±3.44 mm/15s. IOP was as follows: all cygnets 11.30±3.55 mmHg, male cygnets 10.93±3.56 mmHg, female cygnets 11.74±3.50 mmHg. No statistically significant differences between right and left eye and between female and male cygnets were found for IOP and PRTT values. This study provides the reference values for the PRTT and IOP in healthy whooper swan cygnets, showing that PRTT determination of the tear production and rebound tonometry to evaluate the IOP methods are practical methods for ophthalmic examination in swans.