What is the function of the iris,lens and retina?
The iris consists of pigmented fibrovascular tissue known as a stroma. It is the most forward portion of the eye and the only one seen on superficial inspection. The stroma connects a sphincter muscle (sphincter pupillae), which contracts the pupil, and a set of dilator muscles (dilator pupillae) which open it. So, it controls the light level entering the eye, when you are staring at a bright light, the iris contracts to avoid to much light, which can damage the light receptors and thus avoid blindness. The lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina.The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina.The lens is flexible and its curvature is controlled by ciliary muscles. The vertebrate retina is a light sensitive part inside the inn
