How Do Contact Lenses Work?

How Do Contact Lenses Work?

Contact Lenses

If you are one of the 45 million contact lens wearers in the US, you know that they are a great way to correct your vision. But do you know how they actually work? In this blog, we’ll discuss the history of contact lenses, and how they help us see better. 

A Brief History

Contact lenses, as they are thought of today, date back to the late 1800’s, when Dr. Adolf Fick created a lens out of blown glass. These lenses were thick, heavy, and uncomfortable, and could not be worn for more than a few hours at a time. Although Dr. Fick was the first to create a wearable lens, the concept of contact lenses is often credited to Leonardo DaVinci, who discovered that the vision could be altered by placing the head in a bowl of water and looking through the liquid. Over the next century, contact lens designs were improved, and by the late 1940’s, contact lenses were smaller and made of hard plastic, allowing them to be worn for up to 16 hours at a time. By the 1960’s, developments in lens materials led to the manufacture of soft contact lenses, which were significantly more comfortable than their predecessors. The following decade, disposable lenses were developed. Over the last 50 years, contact lenses design and materials have continued to improve, enhancing the safety, comfort, and visual clarity of these corrective lenses.

Refraction

Pencil being refracted in a glass of water

Refraction is the process in which light is bent towards a different direction when it passes through a medium such as air, water, or glass. As the light bends, it changes both where the image appears (farther away or closer to the viewer) and the size of the image. This occurs because light rays pass through different materials at different speeds. Refraction is how contact lenses change images to make them clear to the wearer. 

This image shows the pencil being refracted in water. Notice that the pencil appears “bent” and looks larger when you are viewing it through the water. This is because light passes through water more slowly than through air.

Contacts VS Glasses

Contacts and glasses essentially work the same way. They both bend light via the process of refraction. However, contact lenses and eyeglass lenses are significantly different in design. Contacts are much smaller and thinner than eyeglass lenses. This is made possible by multiple factors:

  1. Contacts are worn directly on the surface of the eye, while glasses are worn several millimeters away. This distance is called the vertex distance. Because the vertex distance is shorter in contact lenses, the power of the lens needed to correct vision is less. The less power in a lens, the less thick they will be.
  2. Lens thickness is directly related to size. As a lens becomes larger, the thickness increases. Because contacts are so small, they are naturally less thick. 

Contact lenses are a great option for most people, and there are many different kinds of contact lenses available. Your eye doctor will discuss your lifestyle and expectations and help you select the correct lenses for your needs. To schedule a contact lens evaluation, call (907) 328-2920.

References:

Centers for Disease Control, Healthy Contact Lens Wear and Care, https://www.cdc.gov/contactlenses/fast-facts.html.

Written by:

Gina Stafford COA, LDO, ABOC

 

Posted in: Uncategorized

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