However, we also find that the developmental clock and the epigenetic clock are not always in synchrony: (1) developmental gradients across the retina are not reflected in DNAm age, (2) organoids are significantly accelerated in DNAm age, despite their similar developmental time with fetal retinas, and (3) the epigenetic clock is significantly accelerated in fetal retina from Down syndrome samples, though the developmental clock does not show major changes and remains correlated with gestational age. The gene discussed is CLOCK; the disease is Down syndrome.