Secondary Photoreceptor Degenerations

Secondary photoreceptor degenerations can be partially distinguished from primary photoreceptor degenerations based upon whether or not correction of the defect in the photoreceptors themselves would be sufficient to arrest photoreceptor death. The distinction is by no means perfect, since there can be genetic mutations that affect directly the survival of photoreceptors as well as the survival of adjacent retinal or retinal pigment epithelium cells that could secondarily be critical for photoreceptor survival. As we attempt to distinguish intrinsic and extrinsic causes of both primary and secondary photoreceptor degenerations, it is increasingly clear that complex interactions and mechanisms can be involved.