The Eye and Vision

How the Eye Works

How does the eye focus light?

The eye works like a camera to focus light and create a clear image. There are two main eye structures that share the job of providing good focus, the cornea, and the lens. The cornea is the window of the eye, much like your car windshield. It is made of living tissue (cells and collagen) that is perfectly clear and shaped with a curved surface. As the light rays enter this curved surface the rays are bent (or refracted), directing the rays closer together and towards the lens. The next structure that light rays encounter is the lens. The lens of the eye is shaped like an M&M candy and is also composed of perfectly clear cells and collagen. The lens also bends the light rays, refracting them towards the posterior surface in the eye, the retina.

Why can’t you see well without glasses?

The eye is amazing! Your body has it’s own auto-focusing camera system with 3-D technology. Clear vision without glasses requires the eye to be a perfect shape and size with each component of the eye doing its job in the focusing process. Looking around the world at the people you see every day it is easy to realize that we all aren’t born with a perfect shape and size. If your eye is bigger or smaller than average, or if each component of the eye (cornea and lens) doesn’t focus perfectly, your vision will be out of focus. Blurry vision due to focusing problems is called Refractive Error. There are three main categories of refractive error: myopia, hyperopia, and astigmatism.

What causes people to be nearsighted (myopia)?

Myopia, or nearsightedness, is a condition of the eye where the focusing power of the eye does not match the size and shape of the eyeball. People who are myopic generally have an eye that is bigger than average or a cornea that has a higher curvature than average. This results in blurred vision for distant objects. One benefit to being myopic is the ability to see things up close without your glasses or contact lenses.

What causes people to be hyperopic?

Hyperopia is caused by an eye that is smaller than average or a cornea that is flatter than it should be. In many people, the auto-focusing ability of the eye is able to help keep an image in focus when the eye is young and healthy. Because of this many hyperopic people don’t need to wear glasses when they are children and young adults. Eventually the auto-focus mechanism ages and blurry vision results, leading to the need for glasses. A hyperopic person can’t see well in the distance or up close without glasses or contact lenses.

What is astigmatism?

Astigmatism is a focusing problem of the eye related to the shape of the cornea. A normal cornea is perfectly round like a basketball. With astigmatism, the eye develops with a slightly oval shape like a football. Astigmatism is corrected with glasses or contact lenses. Almost everyone has a small amount of astigmatism. Astigmatism can be treated with LASIK and PRK. The ICL surgery at this time is limited in the ability to correct significant amounts of astigmatism.

Other than glasses or contact lenses how is refractive error treated?

There are three main methods of surgically treating refractive error. Since the cornea and lens are the two eye structures that focus the light, they are the main structures commonly treated to improve vision. Laser technology can be used to reshape the cornea (LASIK and PRK), and surgical procedures can be done to replace the existing lens (Refractive lens exchange) or simply insert a new lens (Visian ICL).

What is monovision and who should consider it?

Monovision is an option to help people in their 40’s and older to avoid wearing reading glasses. As the eye ages, it loses its ability to focus on items within 18-24 inches. This aging change is called presbyopia. One method to treat presbyopia, monovision, is to use your dominant eye for distance activities (driving, TV) and the other eye for close activities (reading, computer). This is commonly done with contact lenses for people in the mid-40’s and older. If you are in your 40’s and are considering LASIK, PRK, or an ICL implant, monovision may be beneficial for you. If you have not tried monovision, before having a permanent surgery we recommend working with your optometrist in a monovision contact lens trial to make sure you can adjust to it. Benefits of monovision include less need for reading glasses. Some people have difficulty tolerating the different focus between the two eyes and reduced depth perception.

What is co-management?

Dr. DeBry often works closely with your optometrist planning your refractive surgery. Your optometrist may help make some of the initial measurements on your eye to achieve an accurate power selection. The optometrist may also see you for some of the post-operative visits. You have the choice to decide which doctors will participate in your pre- and post-operative care. If your optometrist provides some of these services they will be paid accordingly based on the services they provide. We may elect to have you pay separate payments to our clinic and the optometrist. Please see the co-management consent form located later in this book for more information.


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