After years of study, researchers have come to understand that all retinal degenerative diseases cause vision loss by damaging photoreceptor cells in the retina. However, despite their unique symptoms, RP, Usher syndrome, MD, and related retinal degenerative diseases are all commonly linked by the loss of photoreceptor cells. Photoreceptors are the light sensitive cells in the retina that begin phototransduction - the process of turning light into an electrical signal that is transmitted to the brain via the optic nerve. Rod cells, found mainly in the periphery of the retina, help us see in dark and dimly lit environments. Rod cells also help us see images that come into the periphery of our vision.
Cone cells are densely concentrated in the macula, the center of the retina.
Cone cells perceive fine visual detail and discern colors. They are responsible for central vision, allowing us to read, recognize familiar faces, watch television, sew, and perform other visually detailed tasks. In the initial stages of RP, rod cells begin to degenerate, causing night blindness and a gradual loss of peripheral vision. Unfortunately, due to its progressive nature, RP rarely spares central vision. Once cone cells in the macula degenerate, individuals with MD are left to discern the indistinct images that enter their periphery.