Greater curvature produces greater magnification.
As the curvature increases, the possibility of distortion increases, especially as the diameter of the glass also increases. Generally speaking, it is for this reason that most larger diameter mirrors have less magnification than the smaller diameter styles. As described on this site, this lens is flat on the viewing surface, with a curved rear coated surface. This lens offers distortion-free, 8X magnification, with unlimited focal points. Everyone is able to find their unique focal point, regardless of whether they wear eyeglasses or contacts to see.