CLs: Water gradient technology – applied science and future applications

In-eye wettability has been put forward as one of the main challenges to achieving all-day comfort with contact lenses and may be essential in reducing the high level of contact lens dropout still experienced today. Delefilcon A material was introduced as a unique dual technology combining a low water content silicone hydrogel core, to achieve optimal oxygen supply, with a high water content hydrogel surface to provide a highly lubricious, wettable lens. The objective of this review is to ascertain whether, after several years in use, this technology achieved its intended aim based on review of published literature and completed studies. Material analysis confirmed the water gradient structure of the delefilcon A lens. In vitro analysis of the surface properties demonstrated both a very low coefficient of friction and surface modulus. The clinical literature demonstrated superior on-eye wettability compared to other contact lenses evidenced by a long tear film break-up time, the presence of a continuous tear film during the interblink period, and excellent resistance to dehydration when a break occurs (even in an adverse environment). Minimal tissue interaction was also recorded. Assessments from contact lens users indicated that delefilcon A lenses were preferred over other contact lenses and at least equivalent to spectacles over the course of the day