An adapted abacus, invented by Tim Cranmer, and called a Cranmer abacus is commonly used by visually impaired users.
ɐn ɐdˈæptᵻd ˈæbækəs, ɪnvˈɛntᵻd baɪ tˈɪm kɹˈænmɚ, ænd kˈɔːld ɐ kɹˈænmɚɹ ˈæbækəs ɪz kˈɑːmənli jˈuːzd baɪ vˈɪʒuːəli ɪmpˈɛɹd jˈuːzɚz.