Flies with homozygous visual systems (made using the eyFLP method) and flies in which homozygous clones have been induced in the photoreceptors only (made using the ey3.5FLP system) show severe defects in electroretinogram (ERG) recordings. The ERGs lack both on and off transients, and the hyperpolarization curves are extremely reduced compared to wild type.
The terminals of homozygous R1-R6 photoreceptors form synaptic cartridges in the lamina and the number of synapses is normal, although the number of synaptic terminals per cartridge is more variable than controls. The ratio of mitochondrial area to photoreceptor terminal area is normal. The total number of capitate projections per cartridge is normal, but they are shallower than in wild type.