- Person
- George Wald
- Lived
- 1906–1997
- Field
- Biochemistry of vision
- From
- American
The story
Doctors had known for a long time that people who lacked vitamin A lost the ability to see in dim light, a condition called night blindness. What they did not know was why. In 1932 George Wald, the Brooklyn-born son of Jewish immigrants and a newly trained zoologist from Columbia University, went to Otto Warburg’s laboratory in Berlin to look for the answer in the molecules of the eye itself.
The rod cells of the retina, which handle vision in low light, contain a reddish-purple pigment called rhodopsin that bleaches when light hits it. Wald guessed from its colour that it held a carotenoid, the chemical family that includes vitamin A. He extracted retinas, ran a chemical test, and saw the bright blue colour and light-absorption pattern of vitamin A. He then confirmed the finding with the chemist Paul Karrer in Zürich, using the eyes of cattle, sheep and pigs. In 1933, working in Heidelberg as the Nazis came to power, he found a related yellow substance in frog retinas and proposed a visual cycle: light releases a vitamin A compound from rhodopsin, the compound is recycled, and in the dark the pigment is rebuilt.
Back at Harvard, Wald and his colleagues Ruth Hubbard and Paul Brown filled in the details over the next two decades. They made rhodopsin in a test tube from the protein opsin and retinal, a form of vitamin A, and showed that only a bent form of the molecule, 11-cis retinal, works. Light does one thing: it straightens that molecule, which sets off the nerve signal. The retina then has to bend it back again, using fresh vitamin A from the blood when supplies run low. That is why a diet short of vitamin A leaves the eye unable to rebuild its light sensor fast enough to see at night.
It was the first time anyone had shown what a fat-soluble vitamin actually does in the body. The work, with his studies of the colour-sensing cone pigments, earned him a share of the 1967 Nobel Prize in Physiology or Medicine.
Why it matters
Wald’s visual cycle explains why vitamin A deficiency, which the WHO calls the leading preventable cause of childhood blindness, takes away sight, and it underlies today’s vitamin A programmes and gene therapies such as Luxturna for inherited blindness.
About George Wald
Brooklyn-born biochemist who found vitamin A in the retina and worked out how the eye turns light into sight, explaining night blindness and grounding modern treatment of eye disease.
Sources
- George Wald 1906–1997, Biographical Memoir by John E. Dowling National Academy of Sciences
- George Wald, Biographical NobelPrize.org
- Vitamin A deficiency World Health Organization
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.