This Demonstration shows how the human ocular lens adjusts its convexity in response to the distance of an object from the eyes in order to get a focused image to the retina. Use the sliders to change the distance of the object and watch how the lens becomes more or less convex and how the light rays from the object refract into the retina to get a completely focused image. As the object gets closer, the light converges and requires more refraction from the lens for better focus. If light rays from the object hit the lens, then the lens adjusts so the refraction points exactly to the retina for a focused image.