© 2008 American College of Veterinary Ophthalmologists Veterinary Ophthalmology (2008) 11, Supplement 1, 2–7 Blackwell Publishing Inc Fluorangiographic study of the ocular fundus in normal horses José M. Molleda*, Isabel Cervantes*, Alba Galán*, Rodrigo Tardón†, José M. Gallardo‡ and Eva M. Martín-Suárez* *Department of Animal Medicine and Surgery, University of Cordoba, Cordoba, Spain; †Department of Clinical Sciences, University of Concepción, Santiago de Chile, Chile; ‡Ophthalmology Service, Reina Sofia Hospital, Cordoba, Spain ABSTRACT Purpose: To describe the protocol and appearance of fluorescein angiography (FA) in normal horses. Animals: A total of 25 healthy horses aged between 5 and 15 years. Materials and Methods: The horses were sedated with 15 μg/kg detomidine and 50 μg/kg butorphanol and dilated with topical tropicamide 1%. All angiograms were recorded after intravenous bolus injection of 10 mg/kg of fluorescein sodium solution. Results: Two successive angiographic phases could be discerned: the choriopapillary phase, starting at 46.95 ± 9.48 s, and the retinal vascular phase, starting at 47.79 ± 10.38 s. The retinal vascular phase was divided in three parts: filling phase, maximum fluorescence point, and fading phase. During the filling phase, the dye progressed into the retinal vessels, obtaining maximum fluorescence at 59.79 ± 10.39 s, termed the maximum fluorescence point. The fading phase started immediately following the maximum fluorescence point. During this phase, vascular fluorescence decreased to complete reduction at 74.76 ± 9.81 s. Also, areas of delayed choroidal filling, the presence of short retinal vessels in the ventral region of the optic disc, and a particular filling of the optic disc were also observed. Conclusions: The normal angiographic sequence was described in horses. FA may be a useful method for studying the integrity of the blood–retinal barriers in horses. Key Words: fluorescein angiography, horse, ocular fundus, retinal vessels Address communications to: E. M. Martín-Suárez Tel.: +34 957-12011 Fax: +34 957-211093 e-mail: pv2masue@uco.es INTRODUCTION Relatively little is known about diseases affecting the retina, choroid and optic nerve in horses when compared to dogs and cats. 1 Inactive inflammatory lesions of the peripapillary region are the most common abnormality identified in equine fundus. 1,2 Location and pigmentary changes of inactive chorioretinitis can be observed by ophthalmoscopy. However, other diseases of the equine fundus such as active chorioretinitis, inactive lesions in the tapetal fundus, optic neuritis or optic neuropathy, can be more difficult to identify by ophthalmoscopy. Fluorescein angiography (FA) has been described as a noninvasive and useful test to obtain detailed description of the ocular fundus in animals and providing information about the early alteration of the blood–retinal barrier. 3 FA may be useful for assessing diseases affecting the retinal pigment epithelium, retina/choroid, and optic disc, by delineating areas of involvement, guiding treatment, and formulating a prognosis. To interpret FA images, knowledge of retinal/ choroidal anatomy, and circulation is essential. Differences in arterial and venous circulation, as well as the retina’s barriers against the passage of sodium fluorescein dye including the retinal pigment epithelium (RPE) (outer blood–retinal barrier) and the retinal vascular endothelium (inner blood– retinal barrier), must be understood. 4,5 FA studies and descriptions of angiograms of the equine eye have not been widely reported. 3,6,7 Walde 6 made a super- ficial comparison between dog and horse angiograms and Slatter 7 noted a few pathologic findings using FA. However, normal equine angiographic patterns and technique proto- col have not been fully described. Therefore, the purpose of this paper is to describe the protocol and normal appearance of FA in horses. MATERIALS AND METHODS Animals Fluorangiographic examinations were performed on 25 normal Spanish thoroughbred horses. All horses aged