Abstract: A prescription lens insert and methods of use are described, in which flexing a frame of a prescription lens insert, such that left and right rims of the frame are displaced mediolaterally, aligns respective larger ends of two keyhole apertures of the frame with left and right mushroom-shaped connector pegs protruding rearward from a pair of protective glasses. The prescription lens insert is then placed over the left and right connector pegs, such that distal heads of the connector pegs pass through the two keyhole apertures of the frame and the keyhole apertures are disposed adjacent shaft portions of the connector pegs. The frame of the prescription lens insert is then unflexed to align respective smaller ends of the two keyhole apertures with the left and right connector pegs, such that the distal heads prevent removal of the unflexed frame.