ABSTRACT. In dogs, a variety of diseases of the retina and choroid have been reported, either separately or concomitantly; however, the canine choroid is difficult to evaluate by veterinary techniques currently available. Indocyanine green (ICG) angiography is widely used in human ophthalmology, but has not been investigated for use in canine ophthalmology. The aim of this study was to apply a new approach to ICG angiography and compare the resulting angiograms with fluorescein (FLUO) angiograms of the ocular fundus in dogs. With a fundus camera equipped with an infrared-sensitive charged coupled device (CCD), we performed angiography on eight healthy beagles under inhalation anesthesia. ICG angiography enabled clear visualization of the choroidal vasculature, whereas FLUO angiography showed only the retinal vessels. At 8.4 ± 3.6 sec after administration of ICG dye into the cephalic vein, the choroidal arteries could be seen extending radially from the optic disc, then the choroidal veins became apparent at 10.2 ± 4.1 sec, coursing alongside the choroidal arteries. Gradual fading of the choroidal vessels began 13.2 ± 2.2 min after the dye was administered, and overall diffuse fluorescence of the fundus appeared. Diffuse fluorescence of the fundus continued after the choroidal vessels and optic disc faded at about 58.3 ± 5.3 min from administration of the dye. In conclusion, ICG angiography provides clear resolution and is reliable and simple, thus offering promise as a diagnostic aid for clinical evaluation of the choroid in dogs. KEY WORDS: choroid, dog ophthalmology, fluorescein, indocyanine green, ocular angiography.J. Vet. Med. Sci. 69 (5): [465][466][467][468][469][470] 2007 In the dog eye, retinal circulation can be examined with clarity, but by current veterinary techniques the choroidal circulation eludes examination [7]. Consequently, disorders associated with the choroidal vessels could go undetected until it is too late to ward off deterioration of the animal's vision. Situated between the sclera and the retina, the choroid is a strategic part of the vascular tunic that provides nutritive support to the retina. Given that early recognition of possible ocular pathologic change is paramount to maintaining the eyes in working condition, a new diagnostic approach is needed for the imaging of the vascular structures of the choroid.For examination of retinal circulation, fluorescein (FLUO) angiography is currently used in both human and animal ophthalmology. As a diagnostic tool, the FLUO angiogram provides a reliable guide for laser photocoagulation of exudative and proliferative retinal diseases such as diabetic retinopathy or occlusion of the retinal branch vein [22]. Poor transmission of fluorescence, however, is an inherent characteristic of FLUO dye that limits its usefulness in evaluating either the normal or abnormal choroidal vessels. FLUO dye does not allow visualization through the ocular media opacification, the fundus pigmentation, or through pathologic manifestations [1].In human ophthalmol...

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Model of the dog eyeWith advances in veterinary ophthalmology, instruction of veterinary medical students and medical discussions with clients have been hampered by the lack of a representative canine model. Therefore, we designed the first canine eye model based upon anatomic information from the beagle eye.This model shows the unique features of the canine eye (Fig. 1). The corneal curvature of the dog is larger than that of humans. The site and position of the ocular retractor muscle (not present in humans) surrounding the optic nerve are depicted. The positions of extraocular muscles, insertions and optic nerve are illustrated. The relative ratio of the cornea to the equator of the globe (more than 70%, considerably high than humans) and the iris margin are also correctly depicted.The model is also designed to divide into two hemispheres perpendicularly along the equator permitting observation of intraocular structures (Fig 2). The curvature of the lens is different in the anterior and posterior; the anterior is nearly flat and the posterior is convex. The size of the canine lens from the front to rear axis and along the horizontal axis is larger than in humans, and is approximately two times larger in terms of volume. The inner structure of the iris and pigment changes of the retina are accurately described. The iris, retina and zonular fibers are illustrated in detail and the position of the anterior and posterior chambers of the eye is clearly represented. The ocular fundus shows the optic nerve head (optic disk or papilla), retinal arteries and veins, tapetal fundus, and nontapetal fundus. For comparison, both the normal (clear) lens and cataractous (cloudy) lens are provided. This canine eye model is designed to promote veterinary ophthalmology and was the goal of the late Tadao Kotani, the former professor of veterinary surgery and veterinary ophthalmologist of Rakuno Gakuen University. I would also like to express my sincere gratitude to Mr Tomoaki Honda, CEO of Figure 1.Figure 2.

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