About 7 million cones are present in each retina. By the time the cones deteriorate doctors can see distinctive changes when they look at the retina. All of these changes get worse as the disease progresses. Everyone has a blind spot in each eye where the nerve to the brain connects to the back of the eyeball. To find yours, try the following.
X X Hold the paper away at normal reading distance.
Close your right eye. With your left eye look at the right X but notice the left X in your peripheral vision. Continue looking at the right X as you move the paper toward your eyes. At about 10 inches from your eye, the left X will disappear. Symptoms of RP In RP, rods deteriorate first, then cones.