Light first enters a person's eye through their cornea. Corneas have been compared to the lens cover on a camera. If the lens cover or the cornea is closed by way of the eyelid, then no light enters and you can not see a thing. When they open the light enters and you begin your site. The cornea bends the light next to go toward the pupil.
Your Pupil and Iris
Your pupil is the round black circle in your eye that gets bigger and smaller depending on the amount of light in the room or outside. The iris is the color surrounding the pupil. People can have three basic iris colors: blue, green, and brown. Sometimes individuals can have some varying shades of those three basic colors. The pupil and iris are like a camera's aperture which is an open space that allows the light to pass through farther in to the eye. The light then travels to the lens of your eye.
The lenses of your eye are just like the lenses of a camera. They help to bring the light in to focus. They send the light to the back of the eye. Lenses, just like camera lenses, can become cloudy. This is called a cataract and it must be removed. Cataract surgery is common today and usually done without any complications so that the patient can see clearly again. With a camera, you just have to wipe it clean.
The Retina and the Optical Nerve
In the back of the eye you will find the retina. The retina contains photoreceptor nerve cells. These cells take the light and transform them in to electrical impulses. These electrical impulses are sent to the optic nerve of the eye. The optic nerve then transmit the information to the brain and allows you see to what you see. Using a camera demonstration you can call the retina the film of the camera. If your film goes bad you will not be able to view any pictures no matter what you do. The same goes with the retina. If the retina is damaged you are not going to be able to process any pictures or images. In other words you won't be able to see.