Bledsoe's disease

Bledsoe's Disease was bioengineered by Doctor Kaaldar, an elite Imperial scientist, in the years following the Battle of Yavin. Specific strains of the disease could be released at will, each causing unique reactions. Commonly, Bledsoe's caused the skin to burn, followed gradually by discoloration of the eyes. The discoloration resolved itself into a starfield pattern--dictated by the strain in question. Each pattern was a starmap which revealed the location of a Rebel base. Imperial forces watched for outbreaks of Bledsoe's and used the discoloration as a silent means of communication and strategizing.