The concept of lenses created from silicone hydrogel was first proposed over 20 years ago. The potential advantages were clear however the technological problem was as tough as needing to mix oil and water to provide an optically clear product. Researcher organizations should date invested considerable academic and financial sources to attain the high efficiency delicate lenses of today. They've carried out this fairly just because they see this materials as the way forward and the final word commonplace of the future.
On the time of writing, silicone hydrogel lenses can be found within the USA from four producers: "Night & Day" and "O2OPTIX" from CIBA Vision, "Pure Vision" from Bausch & Lomb, and "Acuvue OASYS" and "Advance" from J&J Vision Care.
OXYGEN TRANSPORT
So what’s so special about silicone hydrogel as a lens material? Essentially, the nice good thing about this materials is it’s means to move oxygen to the attention and thus maintain correct eye health. Trendy contact lens technology is all to do with oxygen permability, which is measured using the "Dk" index. And for optimum oxygen transmission, this should be as high as possible.
The Dk of conventional, non-silicone based hydrogel lenses is immediately associated to the amount of water that the material can hold, since oxygen dissolves into the water-part of the material and thus diffuses by means of the lens. The Dk the truth is will increase logarithmically with growing water content. Water itself has a Dk of solely 80, thus inserting a ceiling on the Dk of convential supplies, and the original tender contact lens material, polyHEMA, possesses a Dk of solely around 10 (with a water content material of about 38%).
Nonetheless, in silicone hydrogels, the relationship between Dk and water content material is the opposite. Here increased water content implies lower Dk. With these lenses Dk increases significantly as the silicone content - not water content - of the lens increases. The Dk values of silicone hydrogel contact lenses are much increased than these of older soft lens materials.
SLEEPING IN CONTACT LENSES
According to market data from CIBA Vision, eighty four% of soft contact lens wearers occasionally sleep with their lenses in, and one-third admit to doing this regularly. 25% of wearers of 1 to two-week disposable lenses with low oxygen transmissibility occasionally or routinely sleep of their lenses overnight. And seventy two% of sentimental contact lens wearers mentioned they would prefer to be allowed to put on their lenses overnight offered it was safe.
Thus the demand for lenses with the capablities of silicone hydrogels is evidently very high with virtually three-quarters of soft lens wearers wanting to have the ability to sleep in their lenses.
LENS HANDLING
Silicone hydrogel lenses are significantly more inflexible than their conventional counterparts, because of the presence of silicone. This increased rigidity does possess some advantages, making the lenses markedly simpler to deal with and thus the best choice for wearers with a less delicate touch. There is a downside to this nonetheless in that the rigidity makes the lenses much less susceptible to adopting the form of the attention so readily, ensuing within the possibility for a few of diminished comfort.
REDUCED DEPOSITIONS
Historically, the deposition of proteins and lipids has been an issue with contact lenses. The quantity of depositions is actually linked to the period of damage, the lens material and the tear composition of every individual wearer. With conventional lenses, a frequent substitute schedule enormously reduces the buildup of dangerous deposits.
Silicone hydrogel contact lenses have been confirmed to supply main advantages within the discount of protein and lysozyme deposition. Indeed, combined with the right alternative schedule and applicable care system, problems related to protein deposition have change into nearly a thing of the past.
DRY EYES
An issue incessantly encountered by wearers of traditional comfortable contact lenses is one in every of a sense of discomfort and "grittiness" within the eyes in the direction of the top of the day. It has been reported that after one week wearing silicone hydrogel lenses, the quantity of normal mushy lens wearers in a selected research group who previously suffered significantly from finish-of-day dryness, was lowered dramatically to only 13% of the sample.
LIFESTYLE BENEFITS
Silicone hydrogel contact lenses additionally provide some benefits that typical lenses don't. Steady put on contact lenses could be particularly beneficial to be used by members of sure professions, comparable to medical workers, police, the armed forces and firefighters who steadily work unpredictable and lengthy hours.
Moreover, an rising numbers of contact lens wearers can now enjoy active out of doors lifestyles, enjoying pursuits corresponding to tenting and climbing where it's often difficult to deal with and disinfect the lenses with the appropriate degree of hygiene.
THE FUTURE FOR CONTACT LENSES
There may be much evidence to suggest that, owing to their important benefits over conventional comfortable lenses, silicone hydrogel lenses will ultimately, and sooner quite than later, displace other forms of contact lens as the prefferred alternative for each every day and in a single day put on for the majority of contact lens wearers. Silicone hydrogel lenses present a much improved physical performance, wonderful dealing with properties and larger comfort. They is likely to be thought-about as the ideal lens for common goal use that exists right now and are prone to turn into the brand new on a regular basis standard.
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