 The Abbe number for a material at a particular refractive index formulation is usually specified as its Abbe value.In practice, a change from 30 to 32 Abbe will not have a practically noticeable benefit, but a change from 30 to 47 could be beneficial for users with strong prescriptions that move their eyes and look "off-axis" of optical center of the lens.Note that some users do not sense color fringing directly but will just describe "off-axis blurriness".