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Tuesday / March 5.
HomeminewsWater Gradient Contact Lenses Begin New Era

Water Gradient Contact Lenses Begin New Era

Optometrists attending a presentation at the Shanghri-la Hotel in early March have been told that in a study conducted by Alcon, “more than 97 per cent of people were successfully fit with Dailies Total1 lenses and nine out of 10 patients were so comfortable they didn’t feel anything”.

An Alcon representative was speaking to optometrists at a key optometry education event in Sydney where the company’s new water gradient contact lens was introduced.

During the presentation the Alcon spokesperson stated that “the release of the first water gradient contact lenses marks the start of yet another new era in comfort for contact lens wearers in Australia and New Zealand and around the world”.

In developing the new lens, Alcon’s researchers had considered the question: “for a lens to be comfortable all day and for long wearing days why have the same water content at the core and surface, or indeed the same material chemistry at the core and surface of a lens?”

The spokesperson said this consideration had led to a radical departure from “single bulk material thinking” and formed the basis for the development of the delefilcon A water gradient lens material.

As a result, “the Dailies Total 1 features a measurable change – from the core to surface – of the lens material for water content and modulus. The water content, for instance changes from 33 per cent at the core to greater than 80 per cent at the surface approaching 100 per cent at the outer surface and achieves a total Dk/t of 156 (-3.00D lens). This is achieved by using a lens material that transitions from a highly breathable silicone hydrogel at the core to an ultrasoft hydrophilic gel at the surface.

“As well as the water content of the lens changing, the modulus of the Dailies Total1 changes – while the outer surface has a compression modulus of <0.025 MPa the lens core maintains a 0.7 MPa modulus. This results in an outer surface that is almost as soft as the corneal epithelium with its integrity maintained by the lens core material and allows for excellent handling characteristics.

“The unique properties at the surface of the lens are key to a comfortable lens wearing experience. The surface co-efficient of friction, or lubricity, has a high correlation with lens comfort scores. We blink about 14,000 times each day and with each blink the superior lid has to slide down, then back up the lens surface. That makes lubricity highly predictive of lens comfort,” said the spokesperson. The surface lubricity was demonstrated by sliding the lenses down an angled surface compared to competitive lenses. He said using the kinetic coefficient of friction, measured by the inclined plate method, delefilcon A has been shown to have extremely low friction, and therefore excellent lubricity.

“With the delefilcon A lens, oxygen transmissibility is measured at the centre of the lens,” said the Alcon spokesperson, adding that starting with the highest available central Dk/t value is therefore the best way to avoid hypoxic concerns, particularly in the lens periphery, and meet the needs of various patient lifestyles.