Model of the dog eye

Abstract

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.

Functional performance of the visual system in dogs and humans: A comparative perspective

“…The cornea is the principal refractive structure for converging light within the eye, and even small changes will have significant impact on visual ability. Although the dog cornea is larger and thicker (see Figure S1) than that in humans (Igarashi, 2005), their cell morphology and functioning are similar (Pigatto et al, 2008). The dog cornea is, depending on breed, 12.5-17 mm in diameter (anterior-posterior surface) and 0.6-0.95 mm in central corneal thickness Tanimura, 1977), indicating extensive variability (see also Table S1).…”

“…This structure differs greatly between dogs and humans (see also Figure S1). The ratio of lens-to-globe is 1:18 in dogs but 1:10 in humans (Beaver, 2009), the lens diameter is 9.5-11 mm (breed dependent) in dogs but 11 mm in humans , its anterior-posterior length (thickness) is ~7 mm in dogs but ~4 mm in humans (Coile, 2007;Igarashi, 2005;, and its anterior radius of curvature is 7.6 mm in dogs but 12 mm in middle-aged humans (Brown, 1974;Dubbelman & Van der Heijde, 2001; see also Table S1). Furthermore, in comparison with humans, the composite fibers of the dog lens are arranged to have a less flexible structure , and the ciliary body that controls the dynamic shape of the lens is also weaker .…”

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“…This structure differs greatly between dogs and humans (see also Figure S1). The ratio of lens-to-globe is 1:18 in dogs but 1:10 in humans (Beaver, 2009), the lens diameter is 9.5-11 mm (breed dependent) in dogs but 11 mm in humans , its anterior-posterior length (thickness) is ~7 mm in dogs but ~4 mm in humans (Coile, 2007;Igarashi, 2005;, and its anterior radius of curvature is 7.6 mm in dogs but 12 mm in middle-aged humans (Brown, 1974;Dubbelman & Van der Heijde, 2001; see also Table S1). Furthermore, in comparison with humans, the composite fibers of the dog lens are arranged to have a less flexible structure , and the ciliary body that controls the dynamic shape of the lens is also weaker .…”