I know I will get hatemail again due to mentioning again the benefits of vitamin A, but the results of the study below are hard to argue with. It appears, vitamin A (retinoic acid) is required for the first step of retinal cell differentiation during fetal development, and thyroid hormone is required for the second one. The role of vitamin A in eyesight has been known for quite some time, to the point that the US Navy ran human experiments during the Cold War with a vitamin A analog trying to get humans to be able to see in the dark like nocturnal animals. Thyroid hormone’s role is less known, but considering the retina is part of the central nervous system and the latter is extremely sensitive to metabolic disturbances, the fact that good thyroid function is required for good vision is not really all that surprising. Ray did recommend thyroid and vitamin A to people with poor eyesight, especially the elderly, as well as serotonin antagonists. Since serotonin is the primary “brake” on oxidative metabolism in the central nervous system, his recommendations make perfect sense, and match the findings of the study below.
https://www.pnas.org/doi/10.1073/pnas.2510799123
https://hub.jhu.edu/2026/02/18/retina-organoids-human-vision/
“…The Johns Hopkins team concluded the distribution of cones in the foveola results from a coordinated process of cell fate specification and conversion during early development. Initially, a sparse number of blue cones are present in the foveola at weeks 10 through 12. But, by week 14, they transform into red and green cones. The patterning occurs by way of two processes, the new study shows. First, a molecule derived from vitamin A called retinoic acid is broken down to limit the creation of blue cones. Second, thyroid hormones encourage blue cones to convert into red and green cones. “First, retinoic acid helps set the pattern. Then, thyroid hormone plays a role in converting the leftover cells,” Johnston said. “That’s very important because if you have those blue cones in there, you don’t see as well.” The findings offer a different perspective to the prevailing theory that blue cones migrate to other parts of the retina during development. Instead, the data suggest that these cells convert to achieve optimal cone distribution in the foveola. “The main model in the field from about 30 years ago was that somehow the few blue cones you get in that region just move out of the way, that these cells decide what they’re going to be, and they remain this type of cell forever,” Johnston said. “We can’t really rule that out yet, but our data supports a different model. These cells actually convert over time, which is really surprising.” The insights could pave the way for new therapies for vision loss.”
Via: https://haidut.me/?p=3000
