My prescription is a strong -7.5 diopters, plus about 2 diopters of astigmatism correction. I have an "easy clip" system with temple-mounted magnets to attach either sunglasses or clear +1.5 reading glasses. For bicycling, single-vision works fine, since I can always slide my glasses down my nose for reading or remove them to read fine print. (The sole benefit of being radically myopic is that one can function quite well without bi/tri-focals.)
__________________
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069