Tonometry and Tear Production Assessment in a Colony of Screech Owls (Megascops asio)
American Association of Zoo Veterinarians Conference 2007

M. Camille Harris1, DVM, MS; Jamie J. Schorling2, DVM; Ian P. Herring2, DVM, MS, DACVO; Francois Elvinger3, DrMedVet., PhD, DACVPM, DECVPH; Patricia R. Bright1, DVM, MS, DACVPM; J. Phillip Pickett2, DVM, DACVO

1The Wildlife Center of Virginia, Waynesboro, VA, USA; 2Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA; 3Department of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA


Approximately 30% of raptors admitted to the Wildlife Center of Virginia from 1996–2005 had ocular injuries. Almost half of these cases were screech owls (Megascops asio). Few avian ophthalmology publications have focused on the family Strigidae. Therefore, the objective of this study was to report ophthalmic findings in the screech owl. Twenty-three, apparently healthy, adult captive screech owls received complete ophthalmic examinations. One randomly assigned eye of each bird was measured by phenol red thread tear test (PRT), and the other eye by Schirmer tear test (STT). TonoVet® (Jorgensen Laboratories, Loveland, CO, USA) rebound tonometry and TonoPen-XL® (Bio-Rad, Inc., Santa Ana, CA, USA) applanation tonometry were performed in each eye to measure intraocular pressure (IOP). Median STT result was ≤2 mm/minute, ranging from ≤2–6 mm/minute, and mean ± standard deviation (SD) PRT was 15±4.3 mm/15 second. In this study, PRT provided more consistently measurable values than STT-I and is recommended for this species. Mean ± SD IOP were 9±1.8 mm Hg TonoVet®-P, 14±2.4 mm Hg TonoVet®-D, and 11±1.9 mm Hg TonoPen-XL®. There are no published manometric studies of IOP in screech owls or other reports of rebound tonometry in birds, so interpretation of which measurement technique is most accurate is not possible at this time. This is the first report of rebound tonometry and PRT in owls. Further studies in tonometry with concurrent manometry are necessary to determine the most accurate IOP measurement technique in this species.


Speaker Information
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M. Camille Harris, DVM, MS
The Wildlife Center of Virginia
Waynesboro, VA, USA

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