Inside of a Dog: What Dogs See, Smell, and Know

by Alexandra Horowitz

Our eyes face forward, and our retinae have foveae: central areas with an extra abundance of photoreceptors. Having so many cells in the center of the retina means that we are very good at seeing things right in front of us in high detail, great focus, and strong color. Perfect for identifying that blob of color and form coming at you as your boyfriend or your mortal enemy. Only primates have foveae. By contrast, dogs have what is called an area centralis: a broad central region with fewer receptors than a fovea, but more than in peripheral parts of the eye. Things directly in front of a dog’s face are visible to him, but they are not quite as sharply in focus as they would be for us. The lens of the eye, which adjusts its curvature to focus light onto the retina, doesn’t accommodate to nearby sources of light. In fact, dogs might overlook small things right in front of their nose (within ten to fifteen inches), because they have fewer retinal cells committed to receiving light from that part of the visual world.