Researchers at the University of Kentucky have discovered one possible cause of dry macular degeneration. The reduction of the Dicer enzyme in the retina is found in patients with geographic atrophy (a condition that causes death of retinal cells). This is caused by an accumulation of a toxic type of RNA, which under normal circumstances would be degraded by the Dicer enzyme. A reduced Dicer enzyme cannot control the toxic RNA and therefore the retinal cells die. The U of K researchers, led by Dr.