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Abstract

A soft contact lens made of a hydrated polymer with an overall water content in the range of 40% to 90% by weight has a water content at the front surface of the lens which is at least 3 percentage points higher than the water content at its rear cornea-contacting surface, as measured by use of an Abbe refractometer. The lens is made from a monomer capable of polymerizing to form a clear transparent partially swollen hydrogel polymer and a diluent forming from 15 to 50% by weight of the moulding mixture, which is moulded between a convex and a concave mould member of different materials chosen so that the lens has the different water contents at its surfaces, as mentioned above. After curing, the mould members are separated with the partially swollen lens adhering to the convex mould member and the whole immersed in an aqueous medium, which may be a weak alkali solution, so as to cause the lens to separate from the convex mould member, to substitute water for any replaceable non-aqueous diluent in the lens, and to cause the lens to swell to substantially its fully hydrated state. The swollen lens is then transferred into saline solution which replaces the water and is packaged and sealed in saline solution in a container. The lens may be sterilized by treatment in an autoclave before and/or after packaging and sealing.

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First Claim