Contact Lens Design & Materials
One-Day Market, Three New Contact Lenses
BY DAVID KADING, OD, FAAO
Daily disposable lenses are the fastest growing contact lens modality. They account for 20% of lens utilization in the United States (Nichols, 2014) and 31% in the rest of the world (Morgan et al, 2014).
Recently, several new contact lenses have entered into the oneday space: Dailies Total1 (Alcon), MyDay (CooperVision), and Miru 1day (Menicon). All of these new lenses offer unique features never before seen in the contact lens market.
Water Gradient Lens
Dailies Total1 (delefilcon A) is unique in its structure in that it transitions from its silicone hydrogel core, which has a water content of 33%, to a water gradient surface, which has a water content greater than 80%.
These characteristics of the lens are related to the crosslinked polymeric wetting agents that are embedded into the core of the lens. The 6-micron-thick water gradient surface provides a very low-silicone surface content, aiding its hydrophilic nature.
Additionally, the delefilcon A material has a Dk/t of 156 at −3.00D, making it the second most breathable disposable contact lens on the market.
Oxygen Delivery Channels
CooperVision’s MyDay daily disposable lenses (stenfilcon A) use a chemical structure called Smart Silicone chemistry to create channels for oxygen delivery. Through this mechanism, the lens does not require as much silicone to achieve its Dk/t of 100 and water content of 54%.
With less silicone, MyDay also has a lower, hydrogel-like modulus. The lens has been released in Europe and will be rolling out elsewhere in the world in 2014.
Flat Pack Technology
Menicon has released the Miru 1day lens into the United States (at this time it is available only in select areas). This marks a milestone for the company; Menicon distributes soft contact lenses worldwide, but this is the first soft lens that the company has released in the United States.
Miru 1day (hioxifilcon A) is a HEMA/GMA-based product that the company states has numerous free hydroxyl radicals that attract and bond water molecules. The molecular structure mimics the oligosaccharides that are found in the mucous layer of the tear film.
One aspect of the Miru 1day lens that sets it apart is its packaging, which is remarkably thin at 1.0mm (Figure 1). A patient wearing Miru 1day lenses can fit six times the number of lenses into the space of a conventional blister pack. In addition, the outer surface of the contact lens is always facing up. This means that fingers never need to come into contact with the inside surface of the lens, and it will help prevent patients from applying their lenses inside out.
Figure 1. The packaging of Miru 1day lenses is only 1mm thick.
The features of these new lenses offer some very unique approaches to help our patients function more comfortably with their contact lenses. All will be great assets to the growing modality of single-use lenses. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #218.
Dr. Kading is in practice in Seattle and is an adjunct faculty member at Pacific University. He is a stock shareholder of Optometric Insights, a consultant or advisor to Alcon, Nicox, and Bausch + Lomb, has an educational grant or contract with Valley Contax, and has received lecture or authorship honoraria from the STAPLE program.