Eye Basics

Dr. Stuart Sondheimer is a well-renowned surgeon providing laser vision correction in Chicago. To help educate his patients on how vision works he has created this page. Please read the information below to better understand how the eye works.

To better understand the many problems and diseases as well as the revolutionary technology available in eye care today, it is important to have a basic understanding of the eye and the “magic” of how we see. By having a better understanding, Chicago LASIK, cataracts and glaucoma patients hopefully will be able to seek medical care early in the disease process and make the choices in treatment that are right for them.

How we see

Basically, the eye is a miraculously complex structure that comes complete its own circulatory system. The process of “seeing” begins when light enters the cornea (clear front portion of the eye) and travels through the eye’s natural crystalline lens where light is focused on the retina (back portion of the eye). The macula of the retina is a small, centrally located area which contains a cuplike depression, also known as the fovea, and is closely packed with cones which give us our most acute, discriminating vision. Once images of light are focused on the macula, the optic nerve sends these images to the brain where they are translated into what we know as “sight.” This process occurs literally millions of times each day and is dependent on the correct function of many physiological functions.

Maintaining the balance

The eye’s natural balance is dependent on a tear system that lubricates the eye and circulatory system that brings blood into the vital structures of the eye such as the retina, choroid, cilliary body, and iris. Tears are secreted by special glands around the eye, some of which are commonly called “tear ducts.” Tear film is composed of basically three layers: mucous, oil and water to spread antibodies and special proteins, provide for comfort and to help resist infection. When the tear film is insufficient, dry eyes, causing an uncomfortable grtitty feeling may occur. When abnormalities in the eye’s circulatory system occur, serious disease such as glaucoma (increased pressure on the optic nerve) or retinal circulatory disorders may result. It is easy to see that all systems must be a “go” in order for the eye to function properly and give us good vision. In fact, the most common problem, refractive error, is often improved with modern procedures such as LASIK or PRK in addition to glasses and/or contact lenses. So whether you are considering LASIK, suffering from diminished vision due to cataracts, or you are concerned about your family history of glaucoma, see your Chicago eye doctor for early diagnosis and state-of-the-art treatment. Remember, your vision is precious! Learn more about eye disorders.

Refractive Errors

The Normal Eye

The normal eye acts as a camera that allows light to converge in a clear point of focus on the retina, which functions like the film in a camera.

Nearsightedness (Myopia)

In the nearsighted eye, the corneal curvature is too steep thus causing light to focus in front of the retina. As a result, distance vision appears blurred.

Farsightedness (Hyperopia)

In the farsighted (hyperopic) eye, the light converges at a point beyond the retina making it difficult to clearly see objects.


The front of the astigmatic eye has an irregular shape, much like a football instead of a baseball, and causes objects to look blurred or double (ghosting).

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Deerfield, IL 60015

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