Representative droplet digital polymerase chain reaction (PCR) results of patient whole-eye tissue (A), retinoblastoma-affected whole-eye tissue (B), and Sturge-Weber syndrome (SWS) brain tissue (C). The dot plots show the droplet fluorescence for the wild-type allele (x-axis) and GNAQ R183Q allele (y-axis). D, GNAQ R183Q allelic frequencies determined by droplet digital PCR in choroidal hemangioma (CH), retinoblastoma (RB), SWS-affected brain, and normal lung tissue. Choroidal vessels were isolated with laser-capture microdissection.