This is likely due to the density of the cells and the intense
brightness of their fluorescent signals prohibiting resolution
of individual cells. This result does not preclude use of the
fundus lens with these transgenic fish where the brightness
of the signal would be an informative experimental outcome.
For example, a loss of total rod opsin protein during photoreceptor
degeneration can be a useful outcome, and longitudinal
studies of inflammation associated with neurodegeneration
often use abundance of glial fibrillary acidic protein abundance
as an informative outcome for assessing treatment
efficacy. Alternatively, one can envisage study of these cells
using transgenic lines that deploy other labeling technologies
or where genetically mosaic animals are available, though we
did not pursue this line of research in this study.