Effect of intravenous administration of romifidine on intraocular pressure in clinically normal horses Mohamed A. Marzok,* Sabry A. El-khodery† and Aiman H. Oheida‡ *Department of Veterinary Surgery, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt; †Department of Internal Medicine and Infectious Diseases, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt; and ‡Department of Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, University of Tripoli, Tripoli 13662, Libya Address communications to: M. A. Marzok Tel.: +2 01222238237 Fax: +2 0473231311 e-mail: marzok2000@hotmail. com Abstract Objective To evaluate the effect of intravenous administration of romifidine on the intraocular pressure (IOP) in horses. Animals studied Twenty-four horses with no ocular abnormalities. Procedure Horses were randomly assigned into two equal groups (treatment and control). All horses in the treatment group received an intravenous (IV) injection of romifidine (40 lg/kg). The horses in the control group were administrated an intravenous injection of 0.9% saline (0.4 mL/100 kg). In both groups, the IOP values were measured immediately (T 0 ) pre-administration and at 5 (T 5 ), 15 (T 15 ), 30 (T 30 ), 45 (T 45 ), 60 (T 60 ), 90 (T 90 ), and 120 (T 120 ) min after drug administration. Results The pre-treatment values (T 0 ) of IOP for right and left eyes were 24.25 Æ 3.5 and 25.16 Æ 3.4 mmHg, respectively. A significant decrease in IOP values was observed in both right and left eyes of the horses in treatment group at T 5 ,T 15 ,T 30 , T 45 ,T 60 , and T 90 in comparison with the baseline values (P < 0.05). The lowest level of IOP in romifidine-treated groups was recorded at T 45 for the right and left eyes (10.25 Æ 2.3 and 11.25 Æ 3.5 mmHg, respectively). Conclusion Romifidine significantly decreased IOP in clinically normal horses and may be used safely for surgery or diagnostic ocular procedures in horses when specific control of IOP is required. Key Words: applanation tonometry, horse, intraocular pressure, romifidine INTRODUCTION Measurement of intraocular pressure (IOP) or tonometry is part of the routine eye examination in horses. 1 In recent years, measurement of IOP in the horse has been revolu- tionized by the development of handheld portable digital tonometers that do not require the horse to be in lateral recumbency. 2 Tonometry is indicated in horses that have ocular disorders such as focal or diffuse corneal edema, red or painful eye, orbital trauma, lens luxation, glaucoma, and uveitis. 3,4 Alpha-2 adrenoceptor agonists, including xylazine, de- tomidine, and romifidine, are used most commonly when performing ophthalmic examination and/or surgical ocular procedures in the horse. 5,6 Standing sedation and analgesia is required on horses to facilitate several ophthalmic diag- nostic tests especially in flighty or very painful animals. 7 For short standing ocular procedures, single intravenous (IV) injection of standard doses of an alpha-2 agonist is often sufficient. For longer procedures, constant rate infu- sion (CRI) may be advantageous over repeated bolus injec- tions to provide a consistent level of sedation. 8 In equine practice, alpha-2 adrenoceptor agonists are also used for premedication in most anesthetic protocols for ophthalmic procedures. The selection of an appropriate anesthetic protocol for intraocular surgery is critical to the success of such procedure. The ability to regulate IOP is considered essential for successful ophthalmic surgery and can be greatly affected by the anesthetic protocol. 9 Therefore, when performing ophthalmic examination or any surgical ocular procedures in horses, the effects of sedation on IOP should be considered. In recent years, several studies have evaluated the effects of anesthetic drugs on IOP values in horses. One study, for example, reported effects of ketamine hydrochloride, prop- ofol, or compounded thiopental sodium administration on © 2014 American College of Veterinary Ophthalmologists Veterinary Ophthalmology (2014) 17, Supplement 1, 149–153 DOI:10.1111/vop.12181