FlyBase curator comment: this entry is used to capture phenotypic information when the particular allele (or allele combination) used by the author could not be determined but the context of the experiment suggests that the phenotype being described is some kind of loss of function.
Flies exposed to light or phorbol esters have an abnormal electroretinogram (ERG); the on- and off-transients are absent, and there is no prolonged depolarising afterpotential in response to maximal-intensity blue light. Spike potentials are seen after illumination with intense light.