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Craig W. Norman, FCLSA
The year 2021 is the 50th anniversary of soft contact lenses for vision correction. Their popularity continues to increase as technology improves, along with the wide acceptance of convenient daily disposables.
There are approximately 42 million1 contact lens wearers in the U.S. However, nearly 7 million have stopped wearing them. While there are many reasons why patients discontinue lens wear, let’s discuss two important contributing factors: compatibility of the lens material to a wearer’s eyes and the on-eye fitting characteristics.
The Soft Lens Material
While there are multiple soft lens material attributes, the two primary ones are oxygen transmission and what is termed “wetting.”
For eye health, oxygen flow received from the surrounding air needs to be maintained. However, wearing a contact lens can disrupt oxygen flow. Therefore, the ideal contact lens will be made of a polymer that allows oxygen to penetrate the material. One such material, silicone hydrogel, is used today to maximize the amount of oxygen reaching the cornea.
Contact lens comfort is achieved by eliminating lens awareness. Lens awareness refers to how much you can feel the lens on the eye. Although there are many possible reasons for this, it’s most often associated with dryness. Studies2 show that for many it’s due to the inability of the lens to remain “wet” on the eye, resulting in dryness later in the day. To help eliminate dryness, a contact lens needs to stay lubricated, ideally mimicking the eye’s natural tear film which lubricates, smooths, and protects the ocular surface.
Some lens materials enhance this wetting by adding a special treatment to the surfaces. One such treatment is called HydraMist® (Tangible® Science) which is only available on the select soft lens daily disposable lenses, Unity BioSync®. This treatment attracts and holds tears on its surfaces, decreasing lens awareness and improving wearing comfort.
Importance of the Lens Fit
A properly fit soft contact lens provides adequate distribution of its weight over the entire corneal surface. This leads to proper lens position, centration, and enough movement to have optimal tear flow, all of which produce minimal mechanical effect between the eye and the contact lens.
Contact lens wearers’ eyes are unique and a lens that fits for one may not fit comfortably for another. Besides the previously described material characteristics, proper contact lens fit depends on the size and curvature of the lens compared to the eye it is being fit on. If the contact lens doesn’t fit properly on the ocular surface, it will produce different pressure points that may result in complications.
Manufacturers of today’s daily disposable lenses attempt to make them as cost-effective as possible for the lens wearer. One way to do so is to limit the sizes and shapes of lenses. In fact, many of the lenses are only available in one size or shape to accommodate the shapes of most eyes.
Another strategy is to offer at least two different shapes of lenses. This shape is called the “base curve.” To ensure the best possible outcome for successful wear, eye doctors prefer to provide base curve options as they know that one shape will not fit everyone equally.
Eye doctors take the proper steps to ensure they provide the best comfort, eye health, and vision for their patients. They choose a soft lens material that stays wet during all-day wear and combine that with choosing the right size or shape of the lens to ensure the proper fit. This provides the disposable soft lens wearer the ability to achieve the all-day comfortable wear they desire.
Mr. Craig W. Norman, FCLSA
During Craig’s career in the contact lens industry, he has been involved in the development and
evaluation of numerous products and technologies in the soft, GP, and scleral lens category. He is
adjunct faculty at the Vision Research Institute at the Michigan College of Optometry, co-curator of
the Contact Lens Museum and the CTO (Chief Thinking Officer) of Wink Productions, Inc. an eye care
training and professional development company.
This blog is for informational purposes only. Plexus Optix and affiliated entities cannot and do not provide professional or medical advice.
1 The Vision Council VisionWatch Eyewear U.S. Study, June 2020
2 Barnett, Brujic, et al; The Role of the Ocular Surface In Contact Lens Wear; CL Spectrum, January 2020
More to Come!
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