To corroborate these findings we therefore evaluated the timing of cognitive decline in a separate cohort of 21 patients diagnosed with classical CLN3 disease from the Dutch national NCL referral center and — to delineate the influence of rapid vision loss — we compared these to a cohort of 13 patients with isolated retinal degeneration due to early onset Stargardt disease. This evidence concerns the gene CLN3 and retinal degeneration.