Your dog’s eyes allow perception of colors, forms, and depth. Their eyes are specially adapted to see well in the dark due to the presence of a tapetum. You can see the yellow-green reflective layer of the tapetum when you shine a light in your dog’s eye in the dark. A dog’s eye is a complex organ that offers a window into the rest of the body. When looking inside the eye with specialized equipment, your veterinarian sees blood vessels, nerves, and lymphoid tissue that cannot be seen in other areas of the body from the outside. Inspection of the inner layers of your dog’s eye reveals whether the cause of the red eye indicates a local problem, (such as conjunctivitis or glaucoma) or a systemic problem (such as retinal bleeding caused by an elevated systemic blood pressure).