A copolymeric hydrogel for contact lenses with physiological saline uptake 65-85% is formed from an N-vinyl lactam e.g. N-vinyl-2-pyrrolidone and up to 15% of a hydrophobic comonomer of formula IMAGE where R1 is H or C1-C4 alkyl (preferably methyl) X is -O- or -NH- and R2 is aryl, C1-C6 alkyl substituted by aryl or aryloxy, or C1-C6 alkoxy substituted by aryl or aryloxy. Preferably the aryl or aryloxy group contain one or two six-membered carbocyclic aromatic rings; they may be C1-C4 alkyl, C1-C4 alkoxy, or halogen, substituted. Crosslinking agents used preferably have their two functional groups differing in reactivity e.g. allyl, or 3-allyloxy-2-hydroxypropyl, methacrylates.
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