Glasses with selectively adjustable optical power lenses

An adjustable power lens assembly comprising one or more frame parts, including a frame body, and an adjustable lens that is mounted to the frame body, the adjustable lens comprising two superposed lens elements, which define an optical axis, the lens elements being slidable relative to one another along an axis of sliding that is in a direction transverse the optical axis and comprising cooperating respective lens surfaces that are shaped to act together to form the adjustable lens, the power of which varies according to the relative disposition of the two lens elements;

• wherein at least one of the lens elements is mounted slidably to the frame body and comprises a plurality of guide formations that cooperate with corresponding formations on the frame body for guiding sliding movement of the at least one lens element relative to the other lens element along the axis of sliding, such that the position of the one lens element relative to the other lens element can be adjusted;
• wherein the plurality of guide formations comprise at least two tabs that protrude outwards from the periphery of the at least one lens element in the same direction as each other and the corresponding formations comprise one or more corresponding channels, the tabs and one or more corresponding channels configured and arranged to define a locus of movement of the at least one lens element relative to the frame body;
• and wherein at least one of the lens elements is mounted slidably to the frame body and is resiliently biased against the frame body in a direction orthogonal to the direction of sliding, thereby registering the lens element to a datum defined by the frame body.