CLN3 and retinal degeneration: Therefore, while the onset timing of the retinal function decline in homozygous Cln3Δex7/8 mice, like in the other Cln3 mouse models, may not coincide with that observed in JNCL patients, there is accumulating evidence that the Cln3 mouse models indeed recapitulate the early features of retinal degeneration in JNCL, and that photoreceptor loss in human patients, which occurs at a much later stage in the mouse models, might result from degenerative processes of the middle and/or inner retina.