Scientists have been trying for years without success to restore sight to the blind. Now, researchers have the first glimmerings that blindness can be reversed.
The experiments began when Manuel del Cerro and co-workers at the University of Rochester used bright light to damage the retinas of lab rats. Del Cerro proved that the rats were blind by using a "startle" test: If animals see a flash of light before hearing a loud noise, they jump less vigorously than if they hear the noise alone. Next, del Cerro implanted rat fetal retinal cells into the rats' damaged retinas.
Previous research had shown that the transplanted tissue survives and makes connections to the nervous system. But the question was whether these connections actually functioned. So del Cerro subjected the rats again to the startle test. By jumping less when they heard the noise, the rats showed that they could at least perceive light. Del Cerro cautions that trials with people are many years away, but he hopes that the technique eventually may be able to tackle some forms of human blindness.