In these units lenses are sometimes paired up with curved mirrors to help make a catadioptric procedure where the lens's spherical aberration corrects the other aberration during the mirror (like Schmidt and meniscus correctors). Your Call lenses will come with crystal clear Directions on how to make use of them, https://rowan65w85.liberty-blog.com/7613076/an-unbiased-view-of-eyes-lenses