More people than ever before are being prescribed daily disposable contact lenses fitted with a toric design. A few reasons for the increased popularity of daily toric lenses has to do with the lenses' great visual quality and convenience. Also, new studies suggest that at least one third of contact wearers now have some form of astigmatism, which means they require a contact lens with a toric design.
Since there are no indications this trend will slow down as the years advance, eye doctors are taking a closer look at how well these lenses allow oxygen to reach the eyes' tissues. They are particularly worried some of these popular lenses could lead to chronic hypoxia, which results from a lack of oxygen reaching the eyes' tissues.
All toric lenses depend on using eyelid stabilization technology in their contact lens design. The change in thickness in certain toric lens designs leads to a decrease in oxygen transmissibility levels (which is usually measured in Dk/t).
Unfortunately, eye doctors can't really rely on most Dk/t measurements nowadays. This has to do with the fact that the standard in the contact lens industry is to publish oxygen transmissibility numbers with just a single value of Dk/t using the geometric centre of a -3.00 lens as a base. This doesn't really work well for toric lenses, which could range in centre thickness from +4.00 to -4.00.
Another problem with the current toric lenses on the market is the fact that there are so few to choose from. Eye doctors are hoping that more daily toric contacts will soon be released that have the ability of releasing the perfect amount of oxygen to eyes of all different sizes.
One toric lens that shows a great deal of promise is the New MyDay toric by CooperVision. Compared to other toric lenses on the market, New MyDay contacts blow away the competition in terms of oxygen permeability. The New MyDay contact with a lens power of -3.00/-0.75x180 had a mean Dk/t score of 54.4, and the -6.00/-0.75x180 lens power New MyDay tested had a Dk/t score of 47.3.
The closest scores using the same lens powers to MyDay came from clariti 1 day toric which had mean scores of 33.7 and 31.2 Dk/t. 1-Day Acuvue Moist for Astigmatism performed the worst with scores of 14.8 and 13.6 mean Dk/t.
Since oxygen transmissibility is such a key component in helping maintain the health and structure of the cornea, doctors believe these CooperVision lenses could be a great option for millions of contact lens wearers around the world. Not only will CooperVision's contacts provide the same comfort as other toric lenses, they will also be able to address issues like astigmatism and reduce the risk for chronic hypoxia.
CooperVision is a division of the multinational medical specialties supplier Cooper Companies. Founded in 1980, CooperVision is currently headquartered in Pleasanton, California. Today, CooperVision sells vision care products to around 100 nations with key distributors in Belgium, the United States, and the United Kingdom.