Albino mammals have specific deficits in their retinae and in the pattern of decussation at their optic chiasm, demonstrating that a melanin-related agent is crucial for normal development of the visual system. Although much attention has been paid to chiasmatic abnormality over the past 30 years, little progress has been made in understanding the abnormality. There has now been a shift of attention towards an analysis of the developing albino retina, which is providing significant advances in our understanding of the role played by this melanin-related agent. It is now possible to identify one candidate substance that emanates from the synthetic pathway of melanin that plays a key role in regulating retinal development.