The protein of the lens had changed, making it opaque and preventing light from reaching the retina .
He tried to imagine a world with colours and brightness but all he could think of was the feeling he got when he stared directly at a light for too long and it burned a red and blue image on his retina when he closed his eyes.
The lens works much like a camera, focusing light onto the retina at the back of the eye.
The chip captures light that enters the eye, and generates an electrical signal that is transmitted to the overlaying neural cells of the retina .
I watched until my eyes hurt, and when I turned away, a black imprint was left on my retina by light too strong to bear.
And for vision it is also necessary that there should be visual purple behind the retina and an opaque cornea and iris.
His dissection of the eye yielded the distinction between cornea, retina , iris, and chorioid coat.
Light rays bounce off the person and onto the retina through the pupil, so if the pupils are large, more light will enter the eyes, and therefore providing a better image.
The flatter cornea then focuses images farther back inside the eyeball, projecting them on the retina instead of in front of it, as is the case in nearsightedness.
As with similar work in the United States, the prosthetic retina works by passing artificially stimulating the optic nerve, in line with signals from a tiny digital camera mounted on a pair of glasses.