Determining whether transgenes targeted to the central nervous system (CNS) are expressed has previously required sacrificing the animal; thus, if a line was to be maintained, it was necessary to generate offspring from the original founder mouse before assay. We describe a method for assaying for the expression of a variety of CNS-targeted transgenes that allows for the survival of the founder mice. Many CNS genes are expressed in the retina, which can be obtained from a mouse by simple survival surgery. We demonstrate that reverse transcription PCR of RNA isolated from a single eye can detect the mRNAs for glial fibrillary acidic protein (GFAP), vimentin, neurofilament light chain (NF-68) and Thy1, all of whose promoters have been used to direct transgene expression in the CNS. We also show that this method readily detects expression of an astrocyte-specific GFAP-driven lacZ transgene and a neuron-specific L7-driven lacZ transgene.