Lip twitch restraint on rebound tonometry in horses

Abstract

ABSTRACT: The purpose of this study was to verify the effect of the upper lip twitch restraint on intraocular pressure (IOP) of healthy horses. In this study, forty five Criollo horses, aged between two to 20 years (male or female) were evaluated with rebound tonometer, with and without upper lip twitch restraint. A previous ophthalmic examination was performed with Schirmer tear test, fluorescein test, slit lamp biomicroscopy and direct ophthalmoscopy in all horses. Only healthy animals with no ocular findings were used. The order of the IOP measurements (with or without twitch) and order of the eye (right or left) were randomized. Three measurements of each eye were made and the mean was calculated. Head position was kept above the heart level and no pressure was made over eyelids. At least 10 minutes passed between the evaluations of the same horse. Measurements were made between 3:30 and 5:30pm to avoid circadian fluctuation of intraocular pressure. Statistical analysis was performed with SAS 9.2 software. A Split plot factorial design was used where horses were considered blocks. The mean intraocular pressure values obtained with lip twitch restraint (34.68±6.47mmHg) were significantly higher (P<0.05) than those obtained without (29.35±4.08mmHg). There was no relevant statistical difference between right and left eyes. The restraint of horses with upper lip twitch increased equine intraocular pressure measured with the rebound tonometry.