Ablend of medical, electronic, and engineering break-throughs has improved the quality of life for many people faced with physical handicaps. New prosthetic limbs can move and flex like the original equipment and even respond to the wearer's own mental commands and cochlear implants let the deaf hear. Blindness, however, has proven less amenable to technological solutions. Yet that, too, may soon change. An assortment of engineers confronting that challenge now expect that, within a few years, those who have lost their sight to degenerative retinal disease will again see the light.