Human Eye Anatomy and Aging Eyes

Eye Anatomy and Anatomy of the Aging Eye

Eye anatomy can help us to understand how human sense of sight perceives an object. As a complex organ, your eyes consist of many parts that give you a sense of sight. Your ability to see depends on the conditions of those parts and how they work together.

When you look at a tree your eyes processing the light it reflects or emits. The light rays from the tree enter the cornea through the pupil and onto the lens. It then progresses through the pupil and the crystalline lens.

Source: National Eye Institute, National Institutes of Health

In the role of focusing light rays, the cornea provides about two-thirds of the eye's focusing power and the lens plays a fine-focusing role. Both of the parts focus the light onto the retina, a delicate tissue that lines the interior walls of the back and sides of the eye. On the retina, the tree image becomes reversed and upside-down.

The central area of the retina is the macula, which provides your best vision. The macula is responsible for your critical focusing vision. You use your macula to stare intensely at an object.

The sensitive retinal tissue then converts the light rays into electrical impulses that are transmitted through the optic nerve, to the back of the brain. Here the electrical impulses are interpreted in an upright tree image.

Human Eye and Camera Analogy

To understand more about eye anatomy and the process of how the eye sees a tree, let's use eye and camera analogy.

An automatic camera's aperture will get smaller when the bright light enters its lens. Similarly, your eyes' pupils will constrict due to the pupillary light response. Like the camera's aperture, the pupils adjust light rays entering your vision system.

A conventional camera needs a lens and a film to produce the tree image. In the same way, the eye employs cornea, crystalline lens and vitreous to focus the light on the retina, as a film. While you develop your camera's film into a positive print, the retina captures the image and sends it to the brain to be developed.

So, if any one or more of these components are not functioning perfectly, the result is a poor tree picture. As with the camera, the eye is only an optical instrument of your visual process. You "don't see" the tree with your eyes. You actually see the tree with your brains.

Anatomy of the Aging Eye and Presbyopia

Beginning at age 40, the eye anatomy is affected by presbyopia -- the difficulty to focus on close objects caused by the natural aging process. The aging process makes the crystalline lens less flexible and the muscles surrounding the lens, which control lens focusing, weak.

The lens can no longer accommodate to increase its power to see near objects clearly. The term accommodate here refers to the thickening ability of eye lens to adjust its focusing distance.

You'll first notice difficulty reading very fine print books. Print seems to have less contrast or blurred and the eyes become easily fatigued when reading the books. If you don't have any other eye problems holding reading material at arm length can help you see clearly.

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